Journal of Cardiovascular Nursing
Vol. 30, No. 1, pp 26Y34 x Copyright B 2015 Wolters Kluwer Health | Lippincott Williams & Wilkins
Cholesterol Screening in US Adults and Awareness of High Cholesterol Among Individuals With Severe Hypertriglyceridemia National Health and Nutrition Examination Surveys 2001Y2008 Jennifer Briley Christian, PharmD, MPH, PhD; Nancy Ellen Bourgeois, BS; Kimberly Anne Lowe, PhD Background: Cholesterol screening is an effective method for identifying individuals with elevated triglyceride levels. Individuals with severe hypertriglyceridemia (SHTG; Q500 mg/dL) have a substantially higher risk for developing coronary heart disease and acute pancreatitis than individuals with lower triglyceride levels. Objective: The aims of this study were to estimate the proportion of US adults who reported having their cholesterol checked, to evaluate the characteristics associated with having cholesterol checked, and to assess factors that are associated with awareness of having high cholesterol among adults with SHTG. Methods: The sample included 7988 adults who participated in the National Health and Nutrition Examination Surveys 2001-2008. Polytomous logistic regression models were used to identify factors that were associated with time since the last cholesterol screening, categorized as never screened, screened less than 2 years ago, and screened 2 or more years ago. Results: Approximately 71% of the US adults reported ever having their cholesterol checked. Only 56% of the individuals with SHTG were aware of having high cholesterol. Factors associated with awareness of high cholesterol among those with SHTG included obesity, education, having insurance, having diabetes, and having a history of cardiovascular events. Conclusions: Most adults in the United States have had their cholesterol checked; however, only half of those with SHTG were aware of having high cholesterol. Awareness is the first step in implementing strategies to attenuate the health risks associated with dyslipidemia. KEY WORDS:
cholesterol, dyslipidemia, hypertriglyceridemia, NHANES, triglycerides
Jennifer Briley Christian, PharmD, MPH, PhD Senior Director, GlaxoSmithKline, Durham, North Carolina.
Nancy Ellen Bourgeois, BS Data Analyst, GlaxoSmithKline, Durham, North Carolina.
Kimberly Anne Lowe, PhD Managing Epidemiologist, Exponent Health Sciences, Bellevue, Washington. This work was conducted and funded by GlaxoSmithKline, with scientific and editorial support from Kimberly Anne Lowe, who is an employee of Exponent. Jennifer Briley Christian is an employee of and holds equity interest in GlaxoSmithKline, and Nancy Ellen Bourgeois is a contracted worker for GlaxoSmithKline. Kim Lowe is currently employed by Amgen Inc, Seattle, WA. All authors meet the criteria for authorship set forth by the International Committee for Medical Journal Editors. Editorial support in the form of development of draft outline and first draft of manuscript, editorial suggestions to draft versions of this paper, assembling tables and figures, collating author comments, copyediting, fact checking, referencing, and overall analysis was provided by Exponent Health Sciences and was funded by GlaxoSmithKline.
Correspondence Jennifer Briley Christian, MPH, PhD, PharmD, GlaxoSmithKline, 5 Moore Dr, B. 3116, Durham, NC 27709-3398 ([email protected]). DOI: 10.1097/JCN.0000000000000101
R
esults from the National Health and Nutrition Examination Survey (NHANES) suggest that approximately 3.4 million American adults (Q20 years of age) have severe hypertriglyceridemia (SHTG; Q500 mg/dL).1 These individuals have a substantially higher risk for developing coronary heart disease (CHD) and acute pancreatitis than do individuals with lower triglyceride (TG) levels.2 Coronary heart disease is the leading cause of death for adults in the United States, accounting for approximately 26% of deaths for both men and women in 2006.3,4 Aggressive efforts to reduce TG levels include behavior modification (such as weight control, increased exercise, reduced dietary fat intake, reduced simple carbohydrate intake, and smoking cessation) and the use of dyslipidemic agents. Despite the fact that almost 68% of Americans with SHTG who participated in the NHANES 2001Y2006 reported having health insurance, only 20% reported taking 1 or more dyslipidemic agents.1 It is plausible that this low prevalence
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Cholesterol Screening and Awareness 27
of treatment use may be attributed to the fact that many individuals with SHTG were unaware of their condition before their participation in the NHANES.1 The current guidelines set forth by the National Cholesterol Education Program Adult Treatment Panel III recommend that all individuals who are 20 years or older have their complete fasting lipid profile (total cholesterol, low-density lipoprotein [LDL] cholesterol, high-density lipoprotein [HDL] cholesterol, and TGs) evaluated once every 5 years and that physicians should clearly communicate the results of these tests to their patients.2 Knowledge of personal cholesterol levels has been shown to have a positive impact on improving health behaviors.5 Unfortunately, information regarding adherence to these guidelines in the United States and the personal factors or characteristics that may be associated with participating in lipid screening is limited. Although previous research has evaluated awareness of cholesterol levels in the US population, there is limited information regarding awareness among individuals with SHTG.6,7 Therefore, using data obtained from NHANES between 2001 and 2008, our objectives were to identify the proportion of Americans who reported having their cholesterol checked and examine the timing of their last screening, to evaluate factors that are associated with having cholesterol checked in the general population, to quantify the percentage of adults with hypertriglyceridemia and SHTG who are aware that they have high cholesterol, and to characterize the demographics and comorbidities associated with being aware of having high cholesterol levels among those with SHTG.
multiyear data sets. Since 1999, NHANES has been conducted as a continuous annual survey and released on public-use data files in 2-year increments. For this study, the NHANES 2001Y2008 surveys were combined to achieve the largest sample possible for the analyses. All adults who participated in the NHANES 2001Y2008 surveys were included in our study, except for people who were younger than 20 years, pregnant and lactating women, and anyone for whom morning, fasting TG levels were not drawn. The national estimates presented herein were obtained using the NHANES sampling weights. The sample weights for NHANES reflect the unequal probabilities of selection, nonresponse adjustments, and adjustments to independent population controls. All analyses are based on the weighted estimates, as suggested from the NHANES analytic guidelines (http://www.cdc.gov/ nchs/data/nhanes/nhanes_03_04/nhanes_analytic_ guidelines_dec_2005.pdf).
Materials and Methods
The following risk factors were included in our analysis and categorized as yes or no unless otherwise specified: gender (male or female), race (non-Hispanic white, Mexican American, non-Hispanic black, and other), age (20Y39, 40Y59, and Q60 years), body mass index (BMI; under/normal weight, G25 kg/m2; overweight, 25Y29.9 kg/m2; and obese, Q30 kg/m2), abdominal obesity (large, Q102 cm for men or Q88 cm for women; normal, G102 cm for men or G88 cm for women), education (less than high school diploma, high school diploma, and more than high school diploma), smoking status (never, current, and former), alcohol consumption (ever or never), health insurance, diagnosed diabetes, history of cardiovascular disease (includes CHD, myocardial infarction, angina, congestive heart failure, or stroke), HDL (Q40 mg/dL and G40 mg/dL), total cholesterol (G200 mg/dL, 200YG240 mg/dL, and Q240 mg/dL), and non-HDL cholesterol (G160 mg/dL, 160YG190 mg/dL, and 190 þ mg/dL). The National Cholesterol Education Program guidelines2 were used to categorize the TG levels as follows: normal (G150 mg/dL), borderline high (150Y199 mg/dL), high (200Y499 mg/dL), and very high TGs (referred to as SHTG in this article; Q500 mg/dL).
Data Source and Study Population Data provided by the NHANES 2001Y2008 surveys were used for this study. Specific details about NHANES have been provided by the Centers for Disease Control and Prevention (CDC) at the following Web site: www .cdc.gov/nchs/nhanes.htm. Briefly, NHANES is a program of studies designed to assess the health and the nutritional status of adults and children in the United States. NHANES provides a valuable set of data because the survey combines interviews with physical examinations and laboratory measures. The NHANES participants were initially interviewed in their homes and then were asked to visit a mobile examination center, where they completed additional questionnaires and underwent a physical examination and blood draw. Data obtained from NHANES are our best resource for estimating the distribution of TG levels as well as the prevalence of hypertriglyceridemia and SHTG in the US adult population. In the past, NHANES surveys were conducted on a periodic basis, and the data were released as single,
Laboratory Methods to Quantify Triglyceride Levels Approximately 50% of the NHANES participants provided a fasting blood sample during a morning examination. All lipid measurements in the NHANES survey were standardized through the CDC National Heart, Lung, and Blood Institute Lipid Standardization Program Methods. A detailed description of measuring TG levels for NHANES can be found elsewhere.8 Patient Characteristics and Classification of the Triglyceride Levels
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28 Journal of Cardiovascular Nursing x January/February 2015 Measures of Cholesterol Awareness The primary outcome in this study was awareness of high cholesterol. Information on this outcome was ascertained directly from the NHANES Blood Pressure and Cholesterol Questionnaires using the following sequential questions: ‘‘Have you ever had your blood cholesterol checked?’’ and ‘‘Has a doctor ever told you that you have high cholesterol?’’ The study participants who answered yes to both of these questions and provided the timing of their last cholesterol screening were categorized as being aware of having high cholesterol. Time since last cholesterol screening was categorized as never screened, screened less than 2 years ago, and screened 2 or more years ago for all subsequent analyses. Statistical Analysis Descriptive statistics, including mean values for continuous variables and percentages for categorical variables, were used to summarize the data. The 95% confidence interval was calculated around all percentages. Univariate and multivariate polytomous logistic regression models were developed to evaluate the association between potential risk factors and time since the study participant’s last cholesterol screening. In these models, those who had never had their cholesterol measured were included as the reference group and were compared with those who had their cholesterol checked within 2 years and with those who had it checked more than 2 years ago. To estimate the adjusted model, we started with a full model that included all variables in the univariate models. We then conducted a backward stepwise regression in which variables with the highest P value were removed one at a time until all of the variables included in the final adjusted model had a P value of 0.20 or less. The # 2 test was used to test the null hypothesis that there is no association between personal characteristics and awareness of high cholesterol levels among individuals with SHTG. Data analyses were conducted using the SAS version 9.1 (SAS Institute, Cary, North Carolina). All statistical tests were considered statistically significant at P G 0.05.
RESULTS Our sample included 7988 adults who participated in the NHANES 2001Y2008 surveys and who provided a fasting blood sample. The distribution of TG levels was as follows: less than 150 mg/dL (68.4%), 150 to G200 mg/dL (14.6%), 200 to G500 mg/dL (15.3%), and 500 mg/dL or greater (1.6%). As illustrated in Figure A, a total of 71% of the sample reported having their cholesterol checked. This approximates a population estimate of 142 million Americans. Approximately 66% of our population reported having their cholesterol checked
FIGURE. On the basis of the national estimates, which were derived from NHANES sampling weights, Figure A illustrates the proportion of the study participants who reported having their cholesterol checked (yes: 142,263,428/200,391,782 = 71%; no: 51,737,937/200,391,782 = 26%; unknown/missing: 6,390,417/200,391,782 = 3%). Figure B illustrates the proportion of the study participants who reported the timing of their last cholesterol screening among those who reported having their cholesterol checked (G1 year: 85,704,851/200,391,782 = 43%; 1YG2 years: 25,704,486/200,391,782 = 13%; 2YG5 years: 19,300,483/200,391,782 = 10%; Q5 years: 10,726,843/ 200,391,782 = 5%; and 58,955,118/200,391,782 = 29%). Figure C illustrates the proportion of the study participants who reported that a doctor has told them that they have high cholesterol (yes: 58,476,860/200,391,782 = 29%; no: 83,150,659/200,391,782 = 42%; unknown/missing: 58,764,263/200,391,782 = 29%).
within the past 5 years. Specific details about the study population are summarized in Table 1, stratified by those who have never had their cholesterol levels screened (n = 2091, 26.8%), those who had it screened less than 2 years ago (n = 4,569, 57.7%), and those who had it screened 2 or more years ago (n = 1019, 15.5%). The results for the univariate and multivariate polytomous regression models are presented in Table 2. The factors that were statistically significantly associated
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Cholesterol Screening and Awareness 29 TABLE 1
Participant Characteristics, by Time Since Last Cholesterol Screening: National Health and Nutrition Examination Surveys 2001Y2008 Never Screened for Cholesterol
Characteristic Gender Male Female Race/ethnicity Mexican American Non-Hispanic white Non-Hispanic black Other Age, mean (95% CI) Body mass index, kg/m2 Underweight /normal (G25.0) Overweight (25.0Y29.9) Obese (Q30.0) Unknown/missing Abdominal obesity, cm e102 (men), e88 (women) 9102 (men), 988 (women) Unknown/missing Education Less than high school High school diploma/GED More than high school Unknown/missing Current smoker Ever used alcohol Have health insurance HDL, mg/dL G40 Q40 Total cholesterol, mg/dL G200 200YG240 240þ Non-HDL cholesterol, mg/dL G160 160YG190 190þ Triglycerides, mg/dL G150 150YG200 200YG500 500þ History of diabetes History of cardiovascular eventsa
Screened for Cholesterol G2 Years
Screened for Cholesterol Q2 Years
n = 2,091
n = 4,569
n = 1,019
N = 51,737,937
N = 111,409,337
N = 30,027,326
% (95% CI)
% (95% CI)
% (95% CI)
56.7 (54.4Y59.0) 43.3 (41.0Y45.6)
46.0 (44.5Y47.5) 54.0 (52.5Y55.5)
50.0 (46.2Y53.8) 50.0 (46.2Y53.8)
14.8 58.6 13.6 12.9 35.0
(12.0Y17.6) (53.8Y63.5) (11.3Y16.0) (9.8Y16.1) (34.2Y35.7)
4.8 75.7 10.7 8.9 52.6
(3.7Y5.9) (72.5Y78.9) (8.6Y12.8) (7.2Y10.6) (51.8Y53.4)
6.2 80.7 7.6 5.5 45.1
(4.6Y7.7) (77.8Y83.6) (6.0Y9.2) (3.9Y7.2) (44.1Y46.1)
40.1 34.1 24.5 1.3
(37.6Y42.6) (31.2Y37.0) (22.2Y26.8) (0.6Y2.0)
28.3 33.7 36.3 1.8
(26.7Y29.8) (31.6Y35.8) (34.3Y38.2) (1.3Y2.4)
33.5 34.3 30.2 2.1
(30.1Y36.8) (30.8Y37.7) (26.9Y33.6) (0.9Y3.2)
59.9 (57.6Y62.2) 37.3 (34.9Y39.8) 2.8 (1.8Y3.8)
39.0 (37.0Y40.9) 58.0 (56.0Y60.1) 3.0 (2.4Y3.6)
51.3 (47.9Y54.7) 45.6 (42.4Y48.7) 3.2 (1.7Y4.7)
27.1 29.4 43.3 0.2 34.6 70.0 60.8
15.8 24.2 60.0 0.0 19.1 64.2 91.9
13.2 24.3 62.4 0 24.5 74.3 79.3
(24.3Y29.9) (26.4Y32.4) (40.4Y46.3) (0.0Y0.4) (31.8Y37.3) (67.1Y72.9) (57.9Y63.7)
(14.0Y17.7) (22.5Y25.8) (57.3Y62.7) (0.0Y0.1) (17.4Y20.8) (61.3Y67.0) (90.7Y93.1)
(10.9Y15.6) (20.9Y27.8) (57.8Y67.1) (20.4Y28.6) (70.2Y78.3) (76.0Y82.5)
18.3 (15.7Y21.0) 81.7 (79.0Y84.3)
16.6 (15.0Y18.2) 83.4 (81.8Y85.0)
18.2 (15.1Y21.2) 81.8 (78.8Y84.9)
65.0 (62.4Y67.5) 24.9 (22.5Y27.3) 10.2 (8.6Y11.7)
52.3 (50.0Y54.5) 32.0 (29.9Y34.0) 15.8 (14.3Y17.2)
46.9 (42.7Y51.1) 34.0 (30.3Y37.8) 19.1 (16.1Y22.1)
74.3 (72.1Y76.6) 15.7 (13.9Y17.4) 10.0 (8.5Y11.6)
66.6 (64.6Y68.5) 20.0 (18.5Y21.5) 13.5 (12.1Y14.9)
60.4 (56.4Y64.4) 20.4 (17.1Y23.7) 19.2 (16.1Y22.3)
74.4 12.5 12.0 1.1 1.9 2.1
65.4 15.9 17.2 1.5 11.6 12.8
67.3 15.2 14.6 2.9 2.9 4.2
(72.3Y76.5) (10.9Y14.2) (10.2Y13.8) (0.6Y1.6) (1.3Y2.5) (1.6Y2.6)
(63.7Y67.1) (14.8Y17.1) (15.8Y18.5) (1.1Y1.9) (10.4Y12.8) (11.4Y14.2)
(63.8Y70.8) (12.6Y17.8) (12.2Y17.1) (1.7Y4.0) (1.7Y4.1) (2.7Y5.6)
Abbreviations: CI, confidence interval; GED, General Education Development; HDL, high-density lipoprotein. a Cardiovascular events include coronary heart disease, myocardial infarction, angina, congestive heart failure, or stroke.
with having a cholesterol screening test for the participants who had been screened either less than 2 years or 2 or more years ago in the multivariate polytomous models were female gender, increased age, higher BMI, and having health insurance compared with those who reported never having their cholesterol checked. Having
a history of diagnosed diabetes or cardiovascular disease resulted in a statistically significant increased likelihood of screening less than 2 years but not 2 or more years ago. Elevated non-HDL cholesterol levels resulted in statistically significant increased odds of screening 2 or more years ago but not less than 2 years. The
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30 Journal of Cardiovascular Nursing x January/February 2015 TABLE 2
Univariate and Multivariate Polytomous Regression Results Comparing Individuals Who Had Their Cholesterol Checked Within 2 Years or 2 or More Years Ago With Those Who Have Never Had It Checked: National Health and Nutrition Examination Surveys 2001Y2008 Cholesterol Screened G2 Years
Categories Gender (ref: male) Female Ethnicity (ref: non-Hispanic white) Mexican American Non-Hispanic black Other Age groups, y (ref: 20Y39) 40Y59 Q60 Body mass index, kg/m2 (ref: underweight/normal [G25.0]) Overweight (25.0Y29.9) Obese (Q30.0) Abdominal obesity (ref: no) Yes Education (ref: more than high school) High school diploma Less than high school Smoking status (ref: never) Current Former Alcohol use (ref: never) Ever Insurance (ref: no) Yes HDL, mg/dL (ref: Q40) G40 Total cholesterol, mg/dL (ref: G200) 200YG240 240þ NonYHDL cholesterol, mg/dL (ref: G160) 160YG190 190þ Triglycerides, mg/dL (ref: G150) 150YG200 200YG500 500þ Diabetes (ref: no) Yes CV history (ref: no) Yes
Cholesterol Screened Q2 Years
Univariate Results, Odds Ratio (95% CI)
Multivariate Results, Odds Ratio (95% CI)a
1.5 (1.4Y1.7)
1.4 (1.2Y1.6)
1.3 (1.1Y1.6)
1.3 (1.1Y1.7)
0.3 (0.2Y0.3) 0.6 (0.5Y0.7) 0.5 (0.4Y0.7)
0.6 (0.5Y0.8) 0.8 (0.7Y1.0) 0.9 (0.7Y1.3)
0.3 (0.2Y0.4) 0.4 (0.3Y0.5) 0.3 (0.2Y0.4)
0.5 (0.4Y0.7) 0.5 (0.4Y0.6) 0.4 (0.3Y0.6)
5.8 (4.9Y6.9) 20.3 (16.8Y24.4)
4.9 (4.0Y6.0) 13.9 (10.8Y18.0)
3.6 (2.8Y4.6) 4.7 (3.6Y6.2)
3.2 (2.4Y4.2) 4.3 (2.9Y6.5)
1.4 (1.2Y1.6) 2.1 (1.8Y2.4)
1.1 (0.9Y1.3) 1.7 (1.2Y2.2)
1.2 (1.0Y1.5) 1.5 (1.2Y1.9)
1.1 (0.9Y1.4) 1.8 (1.2Y2.7)
2.4 (2.1Y2.7)
1.1 (0.9Y1.4)
1.4 (1.2Y1.7)
0.8 (0.6Y1.0)
0.6 (0.50Y0.7) 0.4 (0.4Y0.5)
0.5 (0.4Y0.7) 0.4 (0.3Y0.5)
0.6 (0.4Y0.8) 0.3 (0.3Y0.4)
0.5 (0.4Y0.7) 0.4 (0.3Y0.5)
0.6 (0.5Y0.6) 2.0 (1.6Y2.4)
0.7 (0.6Y0.9) 1.1 (0.9Y1.3)
0.7 (0.5Y0.9) 1.6 (1.3Y2.0)
0.7 (0.5Y1.0) 1.0 (0.8Y1.4)
0.7 (0.6Y0.8)
1.2 (1.0Y1.5)
1.1 (0.9Y1.4)
1.3 (1.0Y1.6)
7.5 (6.5Y8.8)
3.9 (3.3Y4.7)
2.5 (2.1Y3.0)
1.5 (1.3Y1.9)
0.9 (0.7Y1.1)
Not included in the final model
1.0 (0.7Y1.3)
Not included in the final model
1.6 (1.4Y1.9)
Not included in the final model
1.9 (1.6Y2.3)
Not included in the final model
1.9 (1.6Y2.4)
Univariate Results, Multivariate Results, Odds Ratio Odds Ratio (95% CI)a (95% CI)a
2.6 (2.0Y3.4)
1.4 (1.2Y1.7) 1.5 (1.2Y1.9)
1.2 (0.9Y1.5) 1.2 (0.9Y1.6)
1.6 (1.3Y2.1) 2.4 (1.8Y3.1)
1.4 (1.1Y1.9) 1.9 (1.4Y2.7)
1.4 (1.2Y1.7) 1.6 (1.4Y2.0) 1.5 (0.9Y2.5)
1.0 (0.8Y1.3) 1.2 (0.9Y1.5) 1.4 (0.8Y2.6)
1.3 (1.1Y1.7) 1.4 (1.0Y1.8) 2.8 (1.6Y4.9)
1.1 (0.8Y1.4) 1.0 (0.7Y1.3) 2.0 (1.1Y3.7)
6.8 (4.8Y9.8)
3.0 (2.0Y4.6)
1.6 (0.9Y2.6)
1.1 (0.6Y2.0)
6.9 (5.3Y8.9)
2.8 (2.0Y3.8)
2.0 (1.4Y3.0)
1.5 (0.9Y2.5)
Abbreviations: CI, confidence interval; CV, cardiovascular; HDL, high-density lipoprotein; ref, reference. a Variables included in the final multivariate model were selected on the basis of backward stepwise regression methods, in which variables with the highest P value were removed from the model 1 at a time until all of the variables included in the final adjusted model were statistically significantly associated with awareness.
factors that were statistically significantly associated with a decreased likelihood of having a cholesterol screening in both of the multivariate polytomous mod-
els included being Mexican American or non-Hispanic black, having a high school diploma or less education, and being a current smoker.
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Cholesterol Screening and Awareness 31
Approximately 29% of those who reported ever having their cholesterol checked said that a doctor had told them that they have high cholesterol, 42% said that a doctor had not told them that they have high cholesterol, and 29% could not remember or did not answer the survey question (shown in Figure C). The study participants were categorized as being aware of their high cholesterol level if they reported having their blood cholesterol checked and the timing of their last cholesterol screening and reported that a doctor had told them that they have high cholesterol. A total of 42 study participants were not included in these analyses because they did not provide information on the timing of their last cholesterol screening. The level of awareness reported increased with each successive TG category. Specifically, the level of awareness of high cholesterol was approximately 45% among those with TG levels 200 to G500 mg/dL and 55.6% among those with TG levels 500 mg/dL or greater, as shown in Table 3. Table 4 summarizes the characteristics of the survey participants with SHTG, stratified by awareness of having high cholesterol. Several personal characteristics were substantially more common among those who were aware of having high cholesterol levels compared with those who were not aware, including being obese (57.6% vs 26.0%, respectively, P G 0.001), having more than a high school education (63.2% vs 38.5%, respectively, P = 0.05), never using alcohol (40.3% vs 9.1%, respectively, P G 0.001), having health insurance (82.1% vs 55.8%, respectively, P = 0.02), having a history of diagnosed diabetes (26.3% vs 5.2%, respectively, P = 0.008), and having a history of cardiovascular disease (16.0% vs 1.2%, respectively, P G 0.001). Conversely, the factors that are substantially more common among those who were not aware of their high cholesterol levels compared with those who were aware of their high cholesterol levels included being 20 to 39 years of age (47.2% vs 15.9%, respectively, P G 0.001) and being
Mexican American (17.3% vs 4.3%, respectively, P = 0.05).
Discussion It is currently recommended that adults older than 20 years have a complete lipoprotein profile drawn rather than screening for total cholesterol and HDL alone every 5 years.9 The purposes behind this recommendation are to identify individuals who should be taking steps to lower their LDL cholesterol through behavior modification and/or by taking lipid-lowering medications and to recommend treatment beyond LDL lowering for those with TG levels of 200 mg/dL or greater who have reached their LDL goals.10 Our results indicate that approximately 71% of adults in the United States have had their cholesterol checked at least once and 66% of adults had it checked within 5 years. Indeed, approximately 43% of adults have had it checked less than a year ago, which equates to approximately 85 million Americans having had their cholesterol checked less than 1 year ago. There is evidence to suggest that knowledge of personal cholesterol levels may have a positive impact on the implementation of improved health behaviors. In a review of 55 studies from 8 different countries, Bankhead et al5 reported that cholesterol screening generally resulted in improved dietary and exercise habits as well as a reduction in weight among individuals who were informed of their high cholesterol levels. It was also reported that individuals who visited their doctor for cholesterol screening were more likely to return for additional cholesterol screening in the future and were also more likely to participate in other types of health examinations than were individuals who did not get their cholesterol screened. In our study, the factors that were positively associated with having cholesterol screening at any time point included being female, increased age, higher BMI, and having health insurance.
TABLE 3 Proportion of Participants With Elevated Triglyceride Levels Who Are Aware of Their High Cholesterol: National Health and Nutrition Examination Surveys 2001Y2008 Awarea of High Cholesterol
Total Sample TG Levels, mg/dL G150 150YG200 200YG500 Q500
b
Sample, n
Population Estimate, N
Sample, n
Population Estimate,b N
% (95% CI)
5,399 1,220 1,246 123
137,085,669 29,341,488 30,729,562 3,235,063
V V 562 65
V V 13,780,129 1,798,769
V V 44.8 (41.3Y48.4) 55.6 (43.8Y67.4)
Abbreviation: CI, confidence interval; NHANES, National Health and Nutrition Examination Survey; TG, triglyceride. a The study participants were categorized as being aware of having high cholesterol if they reported having their blood cholesterol checked, knew the timing of their last cholesterol screening, and reported that a doctor had told them that they have high cholesterol. A total of 42 study participants were not included in these analyses because they did not provide information on the timing of their last cholesterol screening. b The NHANES provides sampling weights that must be used to produce unbiased national estimates. The sample weights for the NHANES reflect the unequal probabilities of selection, nonresponse adjustments, and adjustments to independent population controls. All analyses are based on the weighted estimates, as suggested from the NHANES analytic guidelines.
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32 Journal of Cardiovascular Nursing x January/February 2015
TABLE 4 Characteristics of Severe Hypertriglyceridemia by Awareness of Having High Cholesterol: National Health and Nutrition Examination Surveys 2001Y2008 Total
Gender Male Female Race/ethnicity Mexican American Non-Hispanic white Non-Hispanic black Other Age groups, y 20Y39 40Y59 Q60 Body mass index, kg/m2 Underweight/normal (G25.0) Overweight (25.0Y29.9) Obese (Q30.0) Abdominal obesity e102 (men), e88 (women) 9102 (men), 988 (women) Education status Less than high school High school diploma/GED More than high school Smoking status Current Former Never Ever use alcohol Yes No Have health insurance Yes No HDL, mg/dL G40 Q40 Total cholesterol, mg/dL G200 200YG240 240þ Non-HDL cholesterol, mg/dL G160 160YG190 190þ History of diabetes Yes No History of cardiovascular eventsb Yes No
Aware of High Cholesterol
Not Aware of High Cholesterol
n = 123
n = 65
n = 58
N = 3,235,063
N = 1,798,769
N = 1,436,294
% (95% CI)
% (95% CI)
% (95% CI)
P
74.6 (63.1Y86.2) 25.4 (13.8Y36.9)
76.3 (62.4Y90.1) 23.7 (9.9Y37.6)
72.5 (55.4Y89.7) 27.5 (10.3Y44.6)
0.71
10.1 68.8 5.5 15.6
4.3 70.1 6.9 18.7
17.3 67.1 3.8 11.8
0.05
(5.6Y14.6) (59.5Y78.0) (2.6Y8.4) (7.4Y23.8)
(1.1Y7.6) (57.8Y82.5) (2.8Y10.9) (6.0Y31.4)
(8.6Y26.1) (55.4Y78.8) (0.0Y8.1) (1.8Y21.8)
29.8 (19.1Y40.5) 56.9 (46.2Y67.6) 13.3 (7.0Y19.6)
15.9 (7.5Y24.4) 64.8 (53.4Y76.1) 19.3 (9.7Y29.0)
47.2 (27.6Y66.7) 47.0 (28.4Y65.7) 5.8 (0.0Y11.6)
G0.001
10.0 (1.6Y18.4) 46.7 (37.3Y56.1) 43.3 (33.7Y52.9)
0.6 (0.0Y1.8) 41.9 (29.3Y54.4) 57.6 (44.9Y70.2)
21.5 (4.3Y38.7) 52.5 (38.0Y67.0) 26.0 (10.0Y42.0)
G0.001
33.3 (21.4Y45.1) 66.7 (54.9Y78.6)
26.0 (11.1Y40.8) 74.0 (59.2Y88.9)
42.0 (22.6Y61.4) 58.0 (38.6Y77.4)
0.20
18.1 (11.9Y24.4) 29.6 (18.2Y41.1) 52.2 (41.2Y63.2)
13.2 (5.0Y21.4) 23.7 (12.0Y35.3) 63.2 (49.7Y76.6)
24.3 (13.0Y35.7) 37.1 (18.1Y56.2) 38.5 (23.1Y54.0)
0.05
34.7 (22.2Y47.1) 31.6 (22.0Y41.3) 33.7 (23.2Y44.2)
27.7 (15.4Y40.0) 38.1 (25.8Y50.4) 34.2 (19.7Y48.7)
43.4 (23.5Y63.3) 23.5 (10.1Y36.9) 33.1 (16.68Y49.6)
0.22
73.2 (61.1Y85.3) 26.8 (14.7Y38.9)
59.7 (40.9 78.5) 40.3 (21.5Y59.1)
90.9 (83.7Y98.1) 9.1 (1.9Y16.4)
G0.001
70.4 (58.6Y82.2) 29.6 (17.75Y41.4)
82.1 (69.3Y94.8) 17.9 (5.2Y30.7)
55.8 (37.3Y74.4) 44.2 (25.7Y62.7)
0.02
71.7 (60.4Y83.0) 28.3 (17.0Y39.6)
67.9 (55.3Y80.5) 32.1 (19.5Y44.7)
76.4 (58.9Y93.9) 23.6 (6.1Y41.1)
0.42
12.2 (5.6Y18.9) 22.0 (13.2Y30.8) 65.8 (55.1Y76.5)
9.2 (1.5Y17.0) 18.2 (8.7Y27.7) 72.6 (61.2Y84.0)
16.0 (4.2Y27.9) 26.8 (12.4Y41.2) 57.2 (39.2Y75.2)
0.28
8.6 (3.1Y14.2) 18.0 (8.4Y27.5) 73.4 (62.9Y83.9)
7.9 (0.5Y15.4) 10.8 (2.4Y19.3) 81.3 (70.6Y92.0)
9.6 (0.5Y18.6) 27.0 (9.3Y44.6) 63.5 (44.0Y83.0)
0.14
17.0 (9.3Y24.6) 83.0 (75.4Y90.7)
26.3 (12.3Y40.4) 73.7 (59.6Y87.7)
5.2 (0.0Y10.9) 94.8 (89.1Y100.0)
0.008
9.5 (3.3Y15.5) 90.5 (84.3Y96.7)
16.0 (5.1Y26.9) 84.0 (73.1Y94.9)
1.2 (0.0Y3.2) 98.8 (96.8Y100.0)
G0.001
Abbreviations: CI, confidence interval; GED, General Education Development; HDL, high-density lipoprotein. a The study participants were categorized as being aware of having high cholesterol if they reported having their blood cholesterol checked, knew the timing of their last cholesterol screening, and reported that a doctor had told them that they have high cholesterol. b Cardiovascular events include coronary heart disease, myocardial infarction, angina, congestive heart failure, or stroke.
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Cholesterol Screening and Awareness 33
What’s New and Important h Although most US adults are having their cholesterol tested, awareness of their levels continues to be poor. h Only half of individuals with elevated TG levels were aware of having high cholesterol. h Awareness is critical for implementing strategies to attenuate the health risks associated with elevated cholesterol.
The factors that were negatively associated with having cholesterol screening at any time point included being Mexican American or non-Hispanic black, having a high school diploma or less education, and being a current smoker. We categorized the participants with SHTG as being aware of having high cholesterol levels if they reported ever having had their cholesterol checked, were told by a doctor that they had high cholesterol, and reported how long it had been since they had their cholesterol checked. Of the study participants with SHTG, only 56% reported being aware of having high cholesterol. Previous studies11Y15 have evaluated the accuracy of self-reported hypercholesterolemia among individuals with total cholesterol levels of 200 mg/dL or greater and found that sensitivity ranged from 41% to 72%, specificity ranged from 75% to 93%, the positive-predictive value ranged from 63% to 88%, and the negativepredictive value ranged from 52% to 85%. It has also been shown that although self-reported cholesterol levels are generally underestimated, these are strongly related to risk for cardiovascular disease.16 The strengths of our study include the large sample size and the use of a nationally representative survey to determine patterns within the US population. NHANES has been a valuable resource for answering questions regarding the epidemiology of dyslipidemia in US adults and children.1,17,18 To our knowledge, this is the first study to evaluate factors that are associated with awareness of high cholesterol among those with SHTG. As expected, the factors that were more common among those who reported being aware of their high cholesterol levels included having a condition that would likely warrant regular doctor visits, including diabetes and previous cardiovascular events. Not surprisingly, the characteristics that were more common among those who were not aware of their high cholesterol levels included low education levels, smoking, alcohol use, and having a large waist circumference. It should be noted that certain key measures within NHANES, such as history of disease, education, and personal habits, rely on self-reported data, which may be subject to issues with recall or other biases.11 However, the prevalence estimates for several chronic conditions and health behaviors related to dyslipidemia
such as heart disease, stroke, hypertension, diabetes, and smoking history were comparable between NHANES and the national averages, as reported by the CDC (www.cdc.gov/DataStatistics/). In summary, we estimate that most adults in America have had their cholesterol checked; however, only half of the Americans with SHTG were aware of having high cholesterol. There continues to be a gap in awareness of cholesterol status, which may serve as the first step in implementing strategies to attenuate the health risks associated with elevated cholesterol.
REFERENCES 1. Christian JB, Bourgeois N, Snipes R, Lowe KA. Prevalence of severe (500 to 2,000 mg/dl) hypertriglyceridemia in United States adults. Am J Cardiol. 2011;107(6):891Y897. 2. National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) final report. Circulation. 2002;106(25):3143Y3421. 3. CDC. Leading causes of death in females: United States http://www.cdc.gov/women/lcod/. Accessed September 30, 2011. 4. CDC. Leading causes of death in males: United States (2006). http://www.cdc.gov/men/lcod/index.htm. Accessed September 30, 2011. 5. Bankhead CR, Brett J, Bukach C, et al. The impact of screening on future health-promoting behaviours and health beliefs: a systematic review. Health Technol Assess. 2003; 7(42):1Y92. 6. Hyre AD, Muntner P, Menke A, Raggi P, He J. Trends in ATP-IIIYdefined high blood cholesterol: prevalence, awareness, treatment and control among U.S. adults. Ann Epidemiol. 2007;17(7):548Y555. 7. Merkin SS, Karlamangla A, Crimmins E, et al. Education differentials by race and ethnicity in the diagnosis and management of hypercholesterolemia: a national sample of U.S. adults (NHANES 1999Y2002). Int J Public Health. 2009; 54(3):166Y174. 8. CDC. NHANES 1999Y2000 Data Documentation (Revised 2007): Lab 13AM - Triglycerides and LDL Cholesterol. Atlanta, GA: CDC; 2007:1Y5. 9. Patel A, Barzi F, Jamrozik K, et al. Serum triglycerides as a risk factor for cardiovascular diseases in the Asia-Pacific region. Circulation. 2004;110(17):2678Y2686. 10. Garber AM, Browner WS, Hulley SB. Cholesterol screening in asymptomatic adults, revisited: part 2. Ann Intern Med. 1996;124(5):518Y531. 11. Natarajan S, Lipsitz SR, Nietert PJ. Self-report of high cholesterol: determinants of validity in U.S. adults. Am J Prev Med. 2002;23(1):13Y21. 12. Bowlin SJ, Morrill BD, Nafziger AN, Jenkins PL, Lewis C, Pearson TA. Validity of cardiovascular disease risk factors assessed by telephone survey: the Behavioral Risk Factor Survey. J Clin Epidemiol. 1993;46(6):561Y571. 13. Colditz GA, Martin P, Stampfer MJ, et al. Validation of questionnaire information on risk factors and disease outcomes in a prospective cohort study of women. Am J Epidemiol. 1986;123(5):894Y900.
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34 Journal of Cardiovascular Nursing x January/February 2015 14. Martin LM, Leff M, Calonge N, Garrett C, Nelson DE. Validation of self-reported chronic conditions and health services in a managed care population. Am J Prev Med 2000;18(3):215Y218. 15. Newell S, Girgis A, Sanson-Fisher R, Ireland M. Accuracy of patients’ recall of Pap and cholesterol screening. Am J Public Health. 2000;90(9):1431Y1435. 16. Huang PY, Buring JE, Ridker PM, Glynn RJ. Awareness, accuracy, and predictive validity of self-reported cholesterol in women. J Gen Intern Med. 2007;22(5):606Y613.
17. Christian JB, Bourgeois NE, Lowe KA. Prevalence, clinical characteristics and treatment patterns of low high-density lipoprotein cholesterol in the US population: National Health and Nutrition Examination Survey 2005Y2008. J Cardiovasc Med (Hagerstown). 2011;12(10):714Y722. 18. Christian JB, Juneja MX, Meadowcroft AM, Borden S, Lowe KA. Prevalence, characteristics, and risk factors of elevated triglyceride levels in US children. Clin Pediatr (Phila). 2011; 50(12):1103Y1109.
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Vol. 30, No. 1, pp 26Y34 x Copyright B 2015 Wolters Kluwer Health | Lippincott Williams & Wilkins
Cholesterol Screening in US Adults and Awareness of High Cholesterol Among Individuals With Severe Hypertriglyceridemia National Health and Nutrition Examination Surveys 2001Y2008 Jennifer Briley Christian, PharmD, MPH, PhD; Nancy Ellen Bourgeois, BS; Kimberly Anne Lowe, PhD Background: Cholesterol screening is an effective method for identifying individuals with elevated triglyceride levels. Individuals with severe hypertriglyceridemia (SHTG; Q500 mg/dL) have a substantially higher risk for developing coronary heart disease and acute pancreatitis than individuals with lower triglyceride levels. Objective: The aims of this study were to estimate the proportion of US adults who reported having their cholesterol checked, to evaluate the characteristics associated with having cholesterol checked, and to assess factors that are associated with awareness of having high cholesterol among adults with SHTG. Methods: The sample included 7988 adults who participated in the National Health and Nutrition Examination Surveys 2001-2008. Polytomous logistic regression models were used to identify factors that were associated with time since the last cholesterol screening, categorized as never screened, screened less than 2 years ago, and screened 2 or more years ago. Results: Approximately 71% of the US adults reported ever having their cholesterol checked. Only 56% of the individuals with SHTG were aware of having high cholesterol. Factors associated with awareness of high cholesterol among those with SHTG included obesity, education, having insurance, having diabetes, and having a history of cardiovascular events. Conclusions: Most adults in the United States have had their cholesterol checked; however, only half of those with SHTG were aware of having high cholesterol. Awareness is the first step in implementing strategies to attenuate the health risks associated with dyslipidemia. KEY WORDS:
cholesterol, dyslipidemia, hypertriglyceridemia, NHANES, triglycerides
Jennifer Briley Christian, PharmD, MPH, PhD Senior Director, GlaxoSmithKline, Durham, North Carolina.
Nancy Ellen Bourgeois, BS Data Analyst, GlaxoSmithKline, Durham, North Carolina.
Kimberly Anne Lowe, PhD Managing Epidemiologist, Exponent Health Sciences, Bellevue, Washington. This work was conducted and funded by GlaxoSmithKline, with scientific and editorial support from Kimberly Anne Lowe, who is an employee of Exponent. Jennifer Briley Christian is an employee of and holds equity interest in GlaxoSmithKline, and Nancy Ellen Bourgeois is a contracted worker for GlaxoSmithKline. Kim Lowe is currently employed by Amgen Inc, Seattle, WA. All authors meet the criteria for authorship set forth by the International Committee for Medical Journal Editors. Editorial support in the form of development of draft outline and first draft of manuscript, editorial suggestions to draft versions of this paper, assembling tables and figures, collating author comments, copyediting, fact checking, referencing, and overall analysis was provided by Exponent Health Sciences and was funded by GlaxoSmithKline.
Correspondence Jennifer Briley Christian, MPH, PhD, PharmD, GlaxoSmithKline, 5 Moore Dr, B. 3116, Durham, NC 27709-3398 ([email protected]). DOI: 10.1097/JCN.0000000000000101
R
esults from the National Health and Nutrition Examination Survey (NHANES) suggest that approximately 3.4 million American adults (Q20 years of age) have severe hypertriglyceridemia (SHTG; Q500 mg/dL).1 These individuals have a substantially higher risk for developing coronary heart disease (CHD) and acute pancreatitis than do individuals with lower triglyceride (TG) levels.2 Coronary heart disease is the leading cause of death for adults in the United States, accounting for approximately 26% of deaths for both men and women in 2006.3,4 Aggressive efforts to reduce TG levels include behavior modification (such as weight control, increased exercise, reduced dietary fat intake, reduced simple carbohydrate intake, and smoking cessation) and the use of dyslipidemic agents. Despite the fact that almost 68% of Americans with SHTG who participated in the NHANES 2001Y2006 reported having health insurance, only 20% reported taking 1 or more dyslipidemic agents.1 It is plausible that this low prevalence
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Cholesterol Screening and Awareness 27
of treatment use may be attributed to the fact that many individuals with SHTG were unaware of their condition before their participation in the NHANES.1 The current guidelines set forth by the National Cholesterol Education Program Adult Treatment Panel III recommend that all individuals who are 20 years or older have their complete fasting lipid profile (total cholesterol, low-density lipoprotein [LDL] cholesterol, high-density lipoprotein [HDL] cholesterol, and TGs) evaluated once every 5 years and that physicians should clearly communicate the results of these tests to their patients.2 Knowledge of personal cholesterol levels has been shown to have a positive impact on improving health behaviors.5 Unfortunately, information regarding adherence to these guidelines in the United States and the personal factors or characteristics that may be associated with participating in lipid screening is limited. Although previous research has evaluated awareness of cholesterol levels in the US population, there is limited information regarding awareness among individuals with SHTG.6,7 Therefore, using data obtained from NHANES between 2001 and 2008, our objectives were to identify the proportion of Americans who reported having their cholesterol checked and examine the timing of their last screening, to evaluate factors that are associated with having cholesterol checked in the general population, to quantify the percentage of adults with hypertriglyceridemia and SHTG who are aware that they have high cholesterol, and to characterize the demographics and comorbidities associated with being aware of having high cholesterol levels among those with SHTG.
multiyear data sets. Since 1999, NHANES has been conducted as a continuous annual survey and released on public-use data files in 2-year increments. For this study, the NHANES 2001Y2008 surveys were combined to achieve the largest sample possible for the analyses. All adults who participated in the NHANES 2001Y2008 surveys were included in our study, except for people who were younger than 20 years, pregnant and lactating women, and anyone for whom morning, fasting TG levels were not drawn. The national estimates presented herein were obtained using the NHANES sampling weights. The sample weights for NHANES reflect the unequal probabilities of selection, nonresponse adjustments, and adjustments to independent population controls. All analyses are based on the weighted estimates, as suggested from the NHANES analytic guidelines (http://www.cdc.gov/ nchs/data/nhanes/nhanes_03_04/nhanes_analytic_ guidelines_dec_2005.pdf).
Materials and Methods
The following risk factors were included in our analysis and categorized as yes or no unless otherwise specified: gender (male or female), race (non-Hispanic white, Mexican American, non-Hispanic black, and other), age (20Y39, 40Y59, and Q60 years), body mass index (BMI; under/normal weight, G25 kg/m2; overweight, 25Y29.9 kg/m2; and obese, Q30 kg/m2), abdominal obesity (large, Q102 cm for men or Q88 cm for women; normal, G102 cm for men or G88 cm for women), education (less than high school diploma, high school diploma, and more than high school diploma), smoking status (never, current, and former), alcohol consumption (ever or never), health insurance, diagnosed diabetes, history of cardiovascular disease (includes CHD, myocardial infarction, angina, congestive heart failure, or stroke), HDL (Q40 mg/dL and G40 mg/dL), total cholesterol (G200 mg/dL, 200YG240 mg/dL, and Q240 mg/dL), and non-HDL cholesterol (G160 mg/dL, 160YG190 mg/dL, and 190 þ mg/dL). The National Cholesterol Education Program guidelines2 were used to categorize the TG levels as follows: normal (G150 mg/dL), borderline high (150Y199 mg/dL), high (200Y499 mg/dL), and very high TGs (referred to as SHTG in this article; Q500 mg/dL).
Data Source and Study Population Data provided by the NHANES 2001Y2008 surveys were used for this study. Specific details about NHANES have been provided by the Centers for Disease Control and Prevention (CDC) at the following Web site: www .cdc.gov/nchs/nhanes.htm. Briefly, NHANES is a program of studies designed to assess the health and the nutritional status of adults and children in the United States. NHANES provides a valuable set of data because the survey combines interviews with physical examinations and laboratory measures. The NHANES participants were initially interviewed in their homes and then were asked to visit a mobile examination center, where they completed additional questionnaires and underwent a physical examination and blood draw. Data obtained from NHANES are our best resource for estimating the distribution of TG levels as well as the prevalence of hypertriglyceridemia and SHTG in the US adult population. In the past, NHANES surveys were conducted on a periodic basis, and the data were released as single,
Laboratory Methods to Quantify Triglyceride Levels Approximately 50% of the NHANES participants provided a fasting blood sample during a morning examination. All lipid measurements in the NHANES survey were standardized through the CDC National Heart, Lung, and Blood Institute Lipid Standardization Program Methods. A detailed description of measuring TG levels for NHANES can be found elsewhere.8 Patient Characteristics and Classification of the Triglyceride Levels
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28 Journal of Cardiovascular Nursing x January/February 2015 Measures of Cholesterol Awareness The primary outcome in this study was awareness of high cholesterol. Information on this outcome was ascertained directly from the NHANES Blood Pressure and Cholesterol Questionnaires using the following sequential questions: ‘‘Have you ever had your blood cholesterol checked?’’ and ‘‘Has a doctor ever told you that you have high cholesterol?’’ The study participants who answered yes to both of these questions and provided the timing of their last cholesterol screening were categorized as being aware of having high cholesterol. Time since last cholesterol screening was categorized as never screened, screened less than 2 years ago, and screened 2 or more years ago for all subsequent analyses. Statistical Analysis Descriptive statistics, including mean values for continuous variables and percentages for categorical variables, were used to summarize the data. The 95% confidence interval was calculated around all percentages. Univariate and multivariate polytomous logistic regression models were developed to evaluate the association between potential risk factors and time since the study participant’s last cholesterol screening. In these models, those who had never had their cholesterol measured were included as the reference group and were compared with those who had their cholesterol checked within 2 years and with those who had it checked more than 2 years ago. To estimate the adjusted model, we started with a full model that included all variables in the univariate models. We then conducted a backward stepwise regression in which variables with the highest P value were removed one at a time until all of the variables included in the final adjusted model had a P value of 0.20 or less. The # 2 test was used to test the null hypothesis that there is no association between personal characteristics and awareness of high cholesterol levels among individuals with SHTG. Data analyses were conducted using the SAS version 9.1 (SAS Institute, Cary, North Carolina). All statistical tests were considered statistically significant at P G 0.05.
RESULTS Our sample included 7988 adults who participated in the NHANES 2001Y2008 surveys and who provided a fasting blood sample. The distribution of TG levels was as follows: less than 150 mg/dL (68.4%), 150 to G200 mg/dL (14.6%), 200 to G500 mg/dL (15.3%), and 500 mg/dL or greater (1.6%). As illustrated in Figure A, a total of 71% of the sample reported having their cholesterol checked. This approximates a population estimate of 142 million Americans. Approximately 66% of our population reported having their cholesterol checked
FIGURE. On the basis of the national estimates, which were derived from NHANES sampling weights, Figure A illustrates the proportion of the study participants who reported having their cholesterol checked (yes: 142,263,428/200,391,782 = 71%; no: 51,737,937/200,391,782 = 26%; unknown/missing: 6,390,417/200,391,782 = 3%). Figure B illustrates the proportion of the study participants who reported the timing of their last cholesterol screening among those who reported having their cholesterol checked (G1 year: 85,704,851/200,391,782 = 43%; 1YG2 years: 25,704,486/200,391,782 = 13%; 2YG5 years: 19,300,483/200,391,782 = 10%; Q5 years: 10,726,843/ 200,391,782 = 5%; and 58,955,118/200,391,782 = 29%). Figure C illustrates the proportion of the study participants who reported that a doctor has told them that they have high cholesterol (yes: 58,476,860/200,391,782 = 29%; no: 83,150,659/200,391,782 = 42%; unknown/missing: 58,764,263/200,391,782 = 29%).
within the past 5 years. Specific details about the study population are summarized in Table 1, stratified by those who have never had their cholesterol levels screened (n = 2091, 26.8%), those who had it screened less than 2 years ago (n = 4,569, 57.7%), and those who had it screened 2 or more years ago (n = 1019, 15.5%). The results for the univariate and multivariate polytomous regression models are presented in Table 2. The factors that were statistically significantly associated
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Cholesterol Screening and Awareness 29 TABLE 1
Participant Characteristics, by Time Since Last Cholesterol Screening: National Health and Nutrition Examination Surveys 2001Y2008 Never Screened for Cholesterol
Characteristic Gender Male Female Race/ethnicity Mexican American Non-Hispanic white Non-Hispanic black Other Age, mean (95% CI) Body mass index, kg/m2 Underweight /normal (G25.0) Overweight (25.0Y29.9) Obese (Q30.0) Unknown/missing Abdominal obesity, cm e102 (men), e88 (women) 9102 (men), 988 (women) Unknown/missing Education Less than high school High school diploma/GED More than high school Unknown/missing Current smoker Ever used alcohol Have health insurance HDL, mg/dL G40 Q40 Total cholesterol, mg/dL G200 200YG240 240þ Non-HDL cholesterol, mg/dL G160 160YG190 190þ Triglycerides, mg/dL G150 150YG200 200YG500 500þ History of diabetes History of cardiovascular eventsa
Screened for Cholesterol G2 Years
Screened for Cholesterol Q2 Years
n = 2,091
n = 4,569
n = 1,019
N = 51,737,937
N = 111,409,337
N = 30,027,326
% (95% CI)
% (95% CI)
% (95% CI)
56.7 (54.4Y59.0) 43.3 (41.0Y45.6)
46.0 (44.5Y47.5) 54.0 (52.5Y55.5)
50.0 (46.2Y53.8) 50.0 (46.2Y53.8)
14.8 58.6 13.6 12.9 35.0
(12.0Y17.6) (53.8Y63.5) (11.3Y16.0) (9.8Y16.1) (34.2Y35.7)
4.8 75.7 10.7 8.9 52.6
(3.7Y5.9) (72.5Y78.9) (8.6Y12.8) (7.2Y10.6) (51.8Y53.4)
6.2 80.7 7.6 5.5 45.1
(4.6Y7.7) (77.8Y83.6) (6.0Y9.2) (3.9Y7.2) (44.1Y46.1)
40.1 34.1 24.5 1.3
(37.6Y42.6) (31.2Y37.0) (22.2Y26.8) (0.6Y2.0)
28.3 33.7 36.3 1.8
(26.7Y29.8) (31.6Y35.8) (34.3Y38.2) (1.3Y2.4)
33.5 34.3 30.2 2.1
(30.1Y36.8) (30.8Y37.7) (26.9Y33.6) (0.9Y3.2)
59.9 (57.6Y62.2) 37.3 (34.9Y39.8) 2.8 (1.8Y3.8)
39.0 (37.0Y40.9) 58.0 (56.0Y60.1) 3.0 (2.4Y3.6)
51.3 (47.9Y54.7) 45.6 (42.4Y48.7) 3.2 (1.7Y4.7)
27.1 29.4 43.3 0.2 34.6 70.0 60.8
15.8 24.2 60.0 0.0 19.1 64.2 91.9
13.2 24.3 62.4 0 24.5 74.3 79.3
(24.3Y29.9) (26.4Y32.4) (40.4Y46.3) (0.0Y0.4) (31.8Y37.3) (67.1Y72.9) (57.9Y63.7)
(14.0Y17.7) (22.5Y25.8) (57.3Y62.7) (0.0Y0.1) (17.4Y20.8) (61.3Y67.0) (90.7Y93.1)
(10.9Y15.6) (20.9Y27.8) (57.8Y67.1) (20.4Y28.6) (70.2Y78.3) (76.0Y82.5)
18.3 (15.7Y21.0) 81.7 (79.0Y84.3)
16.6 (15.0Y18.2) 83.4 (81.8Y85.0)
18.2 (15.1Y21.2) 81.8 (78.8Y84.9)
65.0 (62.4Y67.5) 24.9 (22.5Y27.3) 10.2 (8.6Y11.7)
52.3 (50.0Y54.5) 32.0 (29.9Y34.0) 15.8 (14.3Y17.2)
46.9 (42.7Y51.1) 34.0 (30.3Y37.8) 19.1 (16.1Y22.1)
74.3 (72.1Y76.6) 15.7 (13.9Y17.4) 10.0 (8.5Y11.6)
66.6 (64.6Y68.5) 20.0 (18.5Y21.5) 13.5 (12.1Y14.9)
60.4 (56.4Y64.4) 20.4 (17.1Y23.7) 19.2 (16.1Y22.3)
74.4 12.5 12.0 1.1 1.9 2.1
65.4 15.9 17.2 1.5 11.6 12.8
67.3 15.2 14.6 2.9 2.9 4.2
(72.3Y76.5) (10.9Y14.2) (10.2Y13.8) (0.6Y1.6) (1.3Y2.5) (1.6Y2.6)
(63.7Y67.1) (14.8Y17.1) (15.8Y18.5) (1.1Y1.9) (10.4Y12.8) (11.4Y14.2)
(63.8Y70.8) (12.6Y17.8) (12.2Y17.1) (1.7Y4.0) (1.7Y4.1) (2.7Y5.6)
Abbreviations: CI, confidence interval; GED, General Education Development; HDL, high-density lipoprotein. a Cardiovascular events include coronary heart disease, myocardial infarction, angina, congestive heart failure, or stroke.
with having a cholesterol screening test for the participants who had been screened either less than 2 years or 2 or more years ago in the multivariate polytomous models were female gender, increased age, higher BMI, and having health insurance compared with those who reported never having their cholesterol checked. Having
a history of diagnosed diabetes or cardiovascular disease resulted in a statistically significant increased likelihood of screening less than 2 years but not 2 or more years ago. Elevated non-HDL cholesterol levels resulted in statistically significant increased odds of screening 2 or more years ago but not less than 2 years. The
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30 Journal of Cardiovascular Nursing x January/February 2015 TABLE 2
Univariate and Multivariate Polytomous Regression Results Comparing Individuals Who Had Their Cholesterol Checked Within 2 Years or 2 or More Years Ago With Those Who Have Never Had It Checked: National Health and Nutrition Examination Surveys 2001Y2008 Cholesterol Screened G2 Years
Categories Gender (ref: male) Female Ethnicity (ref: non-Hispanic white) Mexican American Non-Hispanic black Other Age groups, y (ref: 20Y39) 40Y59 Q60 Body mass index, kg/m2 (ref: underweight/normal [G25.0]) Overweight (25.0Y29.9) Obese (Q30.0) Abdominal obesity (ref: no) Yes Education (ref: more than high school) High school diploma Less than high school Smoking status (ref: never) Current Former Alcohol use (ref: never) Ever Insurance (ref: no) Yes HDL, mg/dL (ref: Q40) G40 Total cholesterol, mg/dL (ref: G200) 200YG240 240þ NonYHDL cholesterol, mg/dL (ref: G160) 160YG190 190þ Triglycerides, mg/dL (ref: G150) 150YG200 200YG500 500þ Diabetes (ref: no) Yes CV history (ref: no) Yes
Cholesterol Screened Q2 Years
Univariate Results, Odds Ratio (95% CI)
Multivariate Results, Odds Ratio (95% CI)a
1.5 (1.4Y1.7)
1.4 (1.2Y1.6)
1.3 (1.1Y1.6)
1.3 (1.1Y1.7)
0.3 (0.2Y0.3) 0.6 (0.5Y0.7) 0.5 (0.4Y0.7)
0.6 (0.5Y0.8) 0.8 (0.7Y1.0) 0.9 (0.7Y1.3)
0.3 (0.2Y0.4) 0.4 (0.3Y0.5) 0.3 (0.2Y0.4)
0.5 (0.4Y0.7) 0.5 (0.4Y0.6) 0.4 (0.3Y0.6)
5.8 (4.9Y6.9) 20.3 (16.8Y24.4)
4.9 (4.0Y6.0) 13.9 (10.8Y18.0)
3.6 (2.8Y4.6) 4.7 (3.6Y6.2)
3.2 (2.4Y4.2) 4.3 (2.9Y6.5)
1.4 (1.2Y1.6) 2.1 (1.8Y2.4)
1.1 (0.9Y1.3) 1.7 (1.2Y2.2)
1.2 (1.0Y1.5) 1.5 (1.2Y1.9)
1.1 (0.9Y1.4) 1.8 (1.2Y2.7)
2.4 (2.1Y2.7)
1.1 (0.9Y1.4)
1.4 (1.2Y1.7)
0.8 (0.6Y1.0)
0.6 (0.50Y0.7) 0.4 (0.4Y0.5)
0.5 (0.4Y0.7) 0.4 (0.3Y0.5)
0.6 (0.4Y0.8) 0.3 (0.3Y0.4)
0.5 (0.4Y0.7) 0.4 (0.3Y0.5)
0.6 (0.5Y0.6) 2.0 (1.6Y2.4)
0.7 (0.6Y0.9) 1.1 (0.9Y1.3)
0.7 (0.5Y0.9) 1.6 (1.3Y2.0)
0.7 (0.5Y1.0) 1.0 (0.8Y1.4)
0.7 (0.6Y0.8)
1.2 (1.0Y1.5)
1.1 (0.9Y1.4)
1.3 (1.0Y1.6)
7.5 (6.5Y8.8)
3.9 (3.3Y4.7)
2.5 (2.1Y3.0)
1.5 (1.3Y1.9)
0.9 (0.7Y1.1)
Not included in the final model
1.0 (0.7Y1.3)
Not included in the final model
1.6 (1.4Y1.9)
Not included in the final model
1.9 (1.6Y2.3)
Not included in the final model
1.9 (1.6Y2.4)
Univariate Results, Multivariate Results, Odds Ratio Odds Ratio (95% CI)a (95% CI)a
2.6 (2.0Y3.4)
1.4 (1.2Y1.7) 1.5 (1.2Y1.9)
1.2 (0.9Y1.5) 1.2 (0.9Y1.6)
1.6 (1.3Y2.1) 2.4 (1.8Y3.1)
1.4 (1.1Y1.9) 1.9 (1.4Y2.7)
1.4 (1.2Y1.7) 1.6 (1.4Y2.0) 1.5 (0.9Y2.5)
1.0 (0.8Y1.3) 1.2 (0.9Y1.5) 1.4 (0.8Y2.6)
1.3 (1.1Y1.7) 1.4 (1.0Y1.8) 2.8 (1.6Y4.9)
1.1 (0.8Y1.4) 1.0 (0.7Y1.3) 2.0 (1.1Y3.7)
6.8 (4.8Y9.8)
3.0 (2.0Y4.6)
1.6 (0.9Y2.6)
1.1 (0.6Y2.0)
6.9 (5.3Y8.9)
2.8 (2.0Y3.8)
2.0 (1.4Y3.0)
1.5 (0.9Y2.5)
Abbreviations: CI, confidence interval; CV, cardiovascular; HDL, high-density lipoprotein; ref, reference. a Variables included in the final multivariate model were selected on the basis of backward stepwise regression methods, in which variables with the highest P value were removed from the model 1 at a time until all of the variables included in the final adjusted model were statistically significantly associated with awareness.
factors that were statistically significantly associated with a decreased likelihood of having a cholesterol screening in both of the multivariate polytomous mod-
els included being Mexican American or non-Hispanic black, having a high school diploma or less education, and being a current smoker.
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Cholesterol Screening and Awareness 31
Approximately 29% of those who reported ever having their cholesterol checked said that a doctor had told them that they have high cholesterol, 42% said that a doctor had not told them that they have high cholesterol, and 29% could not remember or did not answer the survey question (shown in Figure C). The study participants were categorized as being aware of their high cholesterol level if they reported having their blood cholesterol checked and the timing of their last cholesterol screening and reported that a doctor had told them that they have high cholesterol. A total of 42 study participants were not included in these analyses because they did not provide information on the timing of their last cholesterol screening. The level of awareness reported increased with each successive TG category. Specifically, the level of awareness of high cholesterol was approximately 45% among those with TG levels 200 to G500 mg/dL and 55.6% among those with TG levels 500 mg/dL or greater, as shown in Table 3. Table 4 summarizes the characteristics of the survey participants with SHTG, stratified by awareness of having high cholesterol. Several personal characteristics were substantially more common among those who were aware of having high cholesterol levels compared with those who were not aware, including being obese (57.6% vs 26.0%, respectively, P G 0.001), having more than a high school education (63.2% vs 38.5%, respectively, P = 0.05), never using alcohol (40.3% vs 9.1%, respectively, P G 0.001), having health insurance (82.1% vs 55.8%, respectively, P = 0.02), having a history of diagnosed diabetes (26.3% vs 5.2%, respectively, P = 0.008), and having a history of cardiovascular disease (16.0% vs 1.2%, respectively, P G 0.001). Conversely, the factors that are substantially more common among those who were not aware of their high cholesterol levels compared with those who were aware of their high cholesterol levels included being 20 to 39 years of age (47.2% vs 15.9%, respectively, P G 0.001) and being
Mexican American (17.3% vs 4.3%, respectively, P = 0.05).
Discussion It is currently recommended that adults older than 20 years have a complete lipoprotein profile drawn rather than screening for total cholesterol and HDL alone every 5 years.9 The purposes behind this recommendation are to identify individuals who should be taking steps to lower their LDL cholesterol through behavior modification and/or by taking lipid-lowering medications and to recommend treatment beyond LDL lowering for those with TG levels of 200 mg/dL or greater who have reached their LDL goals.10 Our results indicate that approximately 71% of adults in the United States have had their cholesterol checked at least once and 66% of adults had it checked within 5 years. Indeed, approximately 43% of adults have had it checked less than a year ago, which equates to approximately 85 million Americans having had their cholesterol checked less than 1 year ago. There is evidence to suggest that knowledge of personal cholesterol levels may have a positive impact on the implementation of improved health behaviors. In a review of 55 studies from 8 different countries, Bankhead et al5 reported that cholesterol screening generally resulted in improved dietary and exercise habits as well as a reduction in weight among individuals who were informed of their high cholesterol levels. It was also reported that individuals who visited their doctor for cholesterol screening were more likely to return for additional cholesterol screening in the future and were also more likely to participate in other types of health examinations than were individuals who did not get their cholesterol screened. In our study, the factors that were positively associated with having cholesterol screening at any time point included being female, increased age, higher BMI, and having health insurance.
TABLE 3 Proportion of Participants With Elevated Triglyceride Levels Who Are Aware of Their High Cholesterol: National Health and Nutrition Examination Surveys 2001Y2008 Awarea of High Cholesterol
Total Sample TG Levels, mg/dL G150 150YG200 200YG500 Q500
b
Sample, n
Population Estimate, N
Sample, n
Population Estimate,b N
% (95% CI)
5,399 1,220 1,246 123
137,085,669 29,341,488 30,729,562 3,235,063
V V 562 65
V V 13,780,129 1,798,769
V V 44.8 (41.3Y48.4) 55.6 (43.8Y67.4)
Abbreviation: CI, confidence interval; NHANES, National Health and Nutrition Examination Survey; TG, triglyceride. a The study participants were categorized as being aware of having high cholesterol if they reported having their blood cholesterol checked, knew the timing of their last cholesterol screening, and reported that a doctor had told them that they have high cholesterol. A total of 42 study participants were not included in these analyses because they did not provide information on the timing of their last cholesterol screening. b The NHANES provides sampling weights that must be used to produce unbiased national estimates. The sample weights for the NHANES reflect the unequal probabilities of selection, nonresponse adjustments, and adjustments to independent population controls. All analyses are based on the weighted estimates, as suggested from the NHANES analytic guidelines.
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32 Journal of Cardiovascular Nursing x January/February 2015
TABLE 4 Characteristics of Severe Hypertriglyceridemia by Awareness of Having High Cholesterol: National Health and Nutrition Examination Surveys 2001Y2008 Total
Gender Male Female Race/ethnicity Mexican American Non-Hispanic white Non-Hispanic black Other Age groups, y 20Y39 40Y59 Q60 Body mass index, kg/m2 Underweight/normal (G25.0) Overweight (25.0Y29.9) Obese (Q30.0) Abdominal obesity e102 (men), e88 (women) 9102 (men), 988 (women) Education status Less than high school High school diploma/GED More than high school Smoking status Current Former Never Ever use alcohol Yes No Have health insurance Yes No HDL, mg/dL G40 Q40 Total cholesterol, mg/dL G200 200YG240 240þ Non-HDL cholesterol, mg/dL G160 160YG190 190þ History of diabetes Yes No History of cardiovascular eventsb Yes No
Aware of High Cholesterol
Not Aware of High Cholesterol
n = 123
n = 65
n = 58
N = 3,235,063
N = 1,798,769
N = 1,436,294
% (95% CI)
% (95% CI)
% (95% CI)
P
74.6 (63.1Y86.2) 25.4 (13.8Y36.9)
76.3 (62.4Y90.1) 23.7 (9.9Y37.6)
72.5 (55.4Y89.7) 27.5 (10.3Y44.6)
0.71
10.1 68.8 5.5 15.6
4.3 70.1 6.9 18.7
17.3 67.1 3.8 11.8
0.05
(5.6Y14.6) (59.5Y78.0) (2.6Y8.4) (7.4Y23.8)
(1.1Y7.6) (57.8Y82.5) (2.8Y10.9) (6.0Y31.4)
(8.6Y26.1) (55.4Y78.8) (0.0Y8.1) (1.8Y21.8)
29.8 (19.1Y40.5) 56.9 (46.2Y67.6) 13.3 (7.0Y19.6)
15.9 (7.5Y24.4) 64.8 (53.4Y76.1) 19.3 (9.7Y29.0)
47.2 (27.6Y66.7) 47.0 (28.4Y65.7) 5.8 (0.0Y11.6)
G0.001
10.0 (1.6Y18.4) 46.7 (37.3Y56.1) 43.3 (33.7Y52.9)
0.6 (0.0Y1.8) 41.9 (29.3Y54.4) 57.6 (44.9Y70.2)
21.5 (4.3Y38.7) 52.5 (38.0Y67.0) 26.0 (10.0Y42.0)
G0.001
33.3 (21.4Y45.1) 66.7 (54.9Y78.6)
26.0 (11.1Y40.8) 74.0 (59.2Y88.9)
42.0 (22.6Y61.4) 58.0 (38.6Y77.4)
0.20
18.1 (11.9Y24.4) 29.6 (18.2Y41.1) 52.2 (41.2Y63.2)
13.2 (5.0Y21.4) 23.7 (12.0Y35.3) 63.2 (49.7Y76.6)
24.3 (13.0Y35.7) 37.1 (18.1Y56.2) 38.5 (23.1Y54.0)
0.05
34.7 (22.2Y47.1) 31.6 (22.0Y41.3) 33.7 (23.2Y44.2)
27.7 (15.4Y40.0) 38.1 (25.8Y50.4) 34.2 (19.7Y48.7)
43.4 (23.5Y63.3) 23.5 (10.1Y36.9) 33.1 (16.68Y49.6)
0.22
73.2 (61.1Y85.3) 26.8 (14.7Y38.9)
59.7 (40.9 78.5) 40.3 (21.5Y59.1)
90.9 (83.7Y98.1) 9.1 (1.9Y16.4)
G0.001
70.4 (58.6Y82.2) 29.6 (17.75Y41.4)
82.1 (69.3Y94.8) 17.9 (5.2Y30.7)
55.8 (37.3Y74.4) 44.2 (25.7Y62.7)
0.02
71.7 (60.4Y83.0) 28.3 (17.0Y39.6)
67.9 (55.3Y80.5) 32.1 (19.5Y44.7)
76.4 (58.9Y93.9) 23.6 (6.1Y41.1)
0.42
12.2 (5.6Y18.9) 22.0 (13.2Y30.8) 65.8 (55.1Y76.5)
9.2 (1.5Y17.0) 18.2 (8.7Y27.7) 72.6 (61.2Y84.0)
16.0 (4.2Y27.9) 26.8 (12.4Y41.2) 57.2 (39.2Y75.2)
0.28
8.6 (3.1Y14.2) 18.0 (8.4Y27.5) 73.4 (62.9Y83.9)
7.9 (0.5Y15.4) 10.8 (2.4Y19.3) 81.3 (70.6Y92.0)
9.6 (0.5Y18.6) 27.0 (9.3Y44.6) 63.5 (44.0Y83.0)
0.14
17.0 (9.3Y24.6) 83.0 (75.4Y90.7)
26.3 (12.3Y40.4) 73.7 (59.6Y87.7)
5.2 (0.0Y10.9) 94.8 (89.1Y100.0)
0.008
9.5 (3.3Y15.5) 90.5 (84.3Y96.7)
16.0 (5.1Y26.9) 84.0 (73.1Y94.9)
1.2 (0.0Y3.2) 98.8 (96.8Y100.0)
G0.001
Abbreviations: CI, confidence interval; GED, General Education Development; HDL, high-density lipoprotein. a The study participants were categorized as being aware of having high cholesterol if they reported having their blood cholesterol checked, knew the timing of their last cholesterol screening, and reported that a doctor had told them that they have high cholesterol. b Cardiovascular events include coronary heart disease, myocardial infarction, angina, congestive heart failure, or stroke.
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Cholesterol Screening and Awareness 33
What’s New and Important h Although most US adults are having their cholesterol tested, awareness of their levels continues to be poor. h Only half of individuals with elevated TG levels were aware of having high cholesterol. h Awareness is critical for implementing strategies to attenuate the health risks associated with elevated cholesterol.
The factors that were negatively associated with having cholesterol screening at any time point included being Mexican American or non-Hispanic black, having a high school diploma or less education, and being a current smoker. We categorized the participants with SHTG as being aware of having high cholesterol levels if they reported ever having had their cholesterol checked, were told by a doctor that they had high cholesterol, and reported how long it had been since they had their cholesterol checked. Of the study participants with SHTG, only 56% reported being aware of having high cholesterol. Previous studies11Y15 have evaluated the accuracy of self-reported hypercholesterolemia among individuals with total cholesterol levels of 200 mg/dL or greater and found that sensitivity ranged from 41% to 72%, specificity ranged from 75% to 93%, the positive-predictive value ranged from 63% to 88%, and the negativepredictive value ranged from 52% to 85%. It has also been shown that although self-reported cholesterol levels are generally underestimated, these are strongly related to risk for cardiovascular disease.16 The strengths of our study include the large sample size and the use of a nationally representative survey to determine patterns within the US population. NHANES has been a valuable resource for answering questions regarding the epidemiology of dyslipidemia in US adults and children.1,17,18 To our knowledge, this is the first study to evaluate factors that are associated with awareness of high cholesterol among those with SHTG. As expected, the factors that were more common among those who reported being aware of their high cholesterol levels included having a condition that would likely warrant regular doctor visits, including diabetes and previous cardiovascular events. Not surprisingly, the characteristics that were more common among those who were not aware of their high cholesterol levels included low education levels, smoking, alcohol use, and having a large waist circumference. It should be noted that certain key measures within NHANES, such as history of disease, education, and personal habits, rely on self-reported data, which may be subject to issues with recall or other biases.11 However, the prevalence estimates for several chronic conditions and health behaviors related to dyslipidemia
such as heart disease, stroke, hypertension, diabetes, and smoking history were comparable between NHANES and the national averages, as reported by the CDC (www.cdc.gov/DataStatistics/). In summary, we estimate that most adults in America have had their cholesterol checked; however, only half of the Americans with SHTG were aware of having high cholesterol. There continues to be a gap in awareness of cholesterol status, which may serve as the first step in implementing strategies to attenuate the health risks associated with elevated cholesterol.
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