Accepted Manuscript Primary care physician visits by patients with incident hypertension Fiona M. Clement, PhD Guanmin Chen, MD, PhD Nadia Khan, MD, MSc Karen Tu, MD, MSc Norm R.C. Campbell, MD Mark Smith, MSc Hude Quan, MD, PhD Brenda R. Hemmelgarn, MD, PhD Finlay A. McAlister, MD, MSc PII:
S0828-282X(14)00191-3
DOI:
10.1016/j.cjca.2014.03.033
Reference:
CJCA 1165
To appear in:
Canadian Journal of Cardiology
Received Date: 28 October 2013 Revised Date:
26 March 2014
Accepted Date: 26 March 2014
Please cite this article as: Clement FM, Chen G, Khan N, Tu K, Campbell NRC, Smith M, Quan H, Hemmelgarn BR, McAlister FA, , Primary care physician visits by patients with incident hypertension, Canadian Journal of Cardiology (2014), doi: 10.1016/j.cjca.2014.03.033. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Primary care physician visits by patients with incident hypertension
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Fiona M Clement, PhDa,b, Guanmin Chen MD, PhDa, b, Nadia Khan, MD, MScc, Karen Tu, MD, MScd, Norm R.C. Campbell, MDa, e, f, Mark Smith, MScg, Hude Quan, MD, PhDa, b, Brenda R. Hemmelgarn, MD, PhDa, b,e, Finlay A. McAlister, MD, MSch for the Hypertension Outcome and Surveillance Team a
Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada Institute of Public Health, University of Calgary, Calgary, Alberta, Canada c Division of General Internal Medicine, University of British Columbia, British Columbia, Vancouver, Canada d Department of Family and Community Medicine, University of Toronto/Institute for Clinical Evaluative Sciences (ICES), Toronto, Ontario, Canada e Department of Medicine, University of Calgary, Calgary, Alberta, Canada f Department of Pharmacology and Therapeutics, University of Calgary, Calgary, Alberta, Canada g Manitoba Centre for Health Policy, University of Manitoba, Winnipeg, Manitoba, Canada h Division of General Internal Medicine, University of Alberta, Edmonton, Ontario, Canada
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Short Title: PCP use among incident hypertensives Corresponding Author:
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Dr. Fiona Clement GD3#18, TRW Building University of Calgary 3280 Hospital Dr NW, Calgary, AB T2N 4Z6 Phone: 403-210-9373 Email: [email protected]
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Word Count: 2645 words, 3 tables, 3 figures, 1 etable
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Brief Summary The study objective is to compare primary care physician (PCP) visits among patients with incident hypertension with and without other comorbidities. Three categories of comorbidities were defined: 1)
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none, 2) vascular risk-related and 3) unrelated. The frequency of PCP visits was high before (88% at least one visit, mean 4.94 per annum) and after (94% at least one visit, mean 6.88 per annum) diagnosis
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of hypertension.
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Abstract (249 words) Background: Access to primary care physicians (PCP) improves health outcomes among patients with hypertension. The study objective is to compare PCP use among patients with incident hypertension
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with and without comorbidities.
Methods: Newly diagnosed hypertensives between April 1, 1998 and March 31, 2009 were identified using Alberta administrative databases. Three comorbidity subgroups were defined: 1) none, 2)
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vascular risk-related, and 3) unrelated. The number of PCP visits was calculated using zero-inflation Poisson regression, with time trends compared using the chi-squared test. A Cox model was used to
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assess the association between PCP utilization and clinical outcomes.
Results: Of 456,263 newly diagnosed hypertensives (mean age 57.6 years, 50.6% men, 62.5% no comorbidity), 88% had seen a PCP in the year pre-diagnosis and 94% in the year following. Compared to pre-diagnosis, the mean number of PCP visits increased after diagnosis (none 3.95 vs.6.15; vascular
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risk-related 6.45 vs. 7.99; and unrelated 6.76 vs.8.24). Over the study period the frequency of prediagnosis PCP visits was constant; there was a statistically significant decline in the adjusted mean number of visits after diagnosis. Those with higher PCP use were less likely to die but more likely to be
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hospitalized regardless of comorbidity.
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Conclusions: The frequency of PCP visits was high before and after diagnosis. Increased PCP use was associated with a lower risk of death, however, it does increase the costs of caring for patients with hypertension, therefore future studies are required to determine the optimal utilization level to achieve cost-effective use of PCP resources.
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Introduction Hypertension is one of the most common chronic conditions world-wide (1) affecting 23% of
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the Canadian adult population (2). It is an important modifiable risk factor for cardiovascular disease and the most common attributable cause for mortality in the world (3;4). More patients visit primary care physicians (PCPs) and receive prescriptions for the treatment of hypertension than any other
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medical disorder (5;6), with more than 4 million prescriptions for antihypertensive medications written every month in Canada (7). The cost in high income countries’ health care systems to manage patients
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with hypertension and related complications is estimated to consume 10% of all health care spending (8;9).
A better understanding of health care resource use for hypertension will enable targeted strategies to be developed to facilitate more cost-effective care. Even small changes in healthcare costs
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to manage hypertension will have a large overall impact given the high prevalence of hypertension in Canada. With an aging Canadian population it is expected that there will be an increase in the burden of hypertension related chronic illnesses, multiple comorbidities, and disability as well as the demand
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for health care services (10). Hypertension Canada, policy makers and health care professionals have made extensive efforts to improve hypertension detection and management through development of
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ongoing national knowledge translation strategies (11;12). Currently in Canada there are no mechanisms in place to monitor hypertension management, hypertension-related outcomes, and health care resource implications. Inefficient care will lead to a significant burden to publically funded health care systems through either inefficient management, or excess hypertension attributable end-organ complications, with attendant implications on health and health care costs. Thus, at a time of unprecedented pressure on our health care system, health care
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leaders are driven to reduce waste and inefficiency. Identifying inefficiencies and factors associated with clinical care gaps in hypertension management is imperative for designing policy and intervention
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programs to close care gaps. To our best knowledge, no studies have documented the pattern of PCP visits after a new diagnosis of hypertension in the universal healthcare system in Canada, and whether the frequency of
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these visits varies by the presence of other comorbid conditions and socioeconomic factors. Given the prevalence and importance of hypertension in the outpatient setting, particularly primary care physician
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offices, this study focused on evaluating the PCP utilization patterns among patients with incident hypertension with and without other comorbidities. Methods Data Sources
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Administrative health databases from Alberta were linked using an anonymized unique personal identifier. The study databases included provincial health insurance registries, hospital discharge abstracts and physician billing claims. The Alberta insurance registry contains demographic
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information including date of birth, sex, and mailing address for all residents of the province eligible to receive health services. Discharge abstracts contain clinical information for all hospitalized patients
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with up to 25 diagnosis codes recorded for each hospitalization using the International Classification of Disease (ICD), 9th Revision (i.e., ICD-9), ICD-9 Clinical Modification (ICD-9-CM) prior to April 2002 or ICD-10 Canadian Modification (i.e., ICD-10-CA) after April 2002 (13-15). Physician billing claims contains fee-for-service billing information that includes a unique physician identifier and ICD-9 codes for services provided. At least one ICD-9 code, and up to three are recorded, corresponding to the primary reasons for each physician visit. Physicians submit claims for payment or reporting services to
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provincial government insurance programs. The physician claims capture outpatient physician services and the majority of inpatient physician services and each claim records the billing physicians’ specialist
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type. Study Population
We defined a cohort of patients newly diagnosed with hypertension between April 1 1998 and
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March 31, 2009 (fiscal years 1998-2008). Hypertension cases were identified using a previously validated case definition for Canadian hospital discharge and physician claims administrative databases
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which was 75% sensitive and 94% specific, with positive predictive value of 81%, when evaluated in the Alberta datasets in the same timeframe as this study (16;17). The first date a hypertension code was specified was defined as the date of diagnosis. We excluded patients with an index date between April 1 1994 and March 31 1997 (i.e., 3 year washout period) to focus on patients with incident
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hypertension. Outcomes
The primary outcome was the mean number of out-patient PCP visits in the year following their
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diagnosis of hypertension. As the majority of patients with hypertension are managed in the
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community by a PCP (Figure 1), only outpatient PCP services were analyzed in this study. Hypertension-related PCP visits and the number of patients with no visits were secondary outcomes. Hypertension-related PCP visits were identified using ICD-9 codes 401.x, 402.x, 403.x, 404.x, or 405.x. Patients with no PCP outpatient visits in the year following diagnosis were considered to have no PCP utilization. To assess the association between PCP utilization and outcomes, death, all cause hospitalization, cardiovascular-specific hospitalization (ICD codes G45, G46, I60 - I69, H340, I43, I50, I099, I110, I130, I132, I255, I420, I425 - I429, P290, I21, I22, I252 as the most responsible diagnosis) 6
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and hypertension-specific hospitalization (ICD codes 401.x, 402.x, 403.x, 404.x, or 405.x as the most responsible diagnosis) were considered. All outcomes were defined 1 year following hypertension
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diagnosis. Exposure Variables
Comorbidity status, defined using the Charlson comorbidities, was the exposure variable. All
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comorbidities were derived from validated ICD9/ICD10 algorithms using both the hospital discharge abstract data and the physician claims database for the three years prior to hypertension diagnosis
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(18;19). Three categories of comorbidity were considered: 1) no comorbidity, 2) vascular risk-related comorbidity (myocardial infarction, congestive heart failure, peripheral vascular disease, and cerebrovascular disease, diabetes with and without complications and renal disease) and 3) unrelated comorbidity (ie. unrelated to vascular risk including dementia, chronic pulmonary obstructive disease,
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connective tissue disease, rheumatic disease, peptic ulcer disease, paraplegia/hemiplegia, liver disease, cancer/metastatic carcinoma and AIDS/HIV). In the analysis considering clinical outcomes, PCP utilization was the exposure variable, and categorized based on utilization within other healthcare
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Independent Variables
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settings (20) as ≤ 2 visits per year, 2-5 visits per year and ≥ 5 visits per year.
Age and sex at index date of hypertension diagnosis were defined using the registry data. Age was categorized into 6 groups: under 35, 35-45, 45-55, 55-65, 65-75 and over 75 years of age. Median income quintile was assigned using 2001 Statistics Canada Census data and each patient’s postal code forward sortation area. Statistical Analysis
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Baseline characteristics of patients with incident hypertension were analyzed descriptively. To provide a baseline measure of utilization, all outcomes were calculated for both the year preceding and following hypertension diagnosis. The number of PCP visits in the year preceding and the year
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following diagnosis was estimated using zero-inflation Poisson regression to account for the overdispersion due to excessive zeros counts. If the Poisson assumption that variance is equal to the mean was not met, negative binominal regression was used. If hypertension was defined using physician
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claims, the 2 visits required to meet the definition of hypertension were not included in estimates of the mean number of visits. Both crude and adjusted means are reported. The adjusted model included age
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group, sex, income quintile, rural/urban, and year of diagnosis. To assess if utilization patterns have changed over time, the mean number of PCP visits was calculated by year of diagnosis. A chi-squared test for trend was completed for each comorbidity group over time. A proportional hazard Cox model was completed to assess the association between PCP utilization and clinical outcomes including death,
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and all cause-, cardiovascular- and hypertension-specific hospitalization. Due to the time-dependent nature of PCP exposure, only adjusted analyses are considered. A time-dependent variable was included to account for the relationship between PCP utilization and exposure time. All analyses were
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adjusted for age, sex, income quintile, rural/urban and year of diagnosis. The statistical analyses were conducted using Statistical Analysis software (SAS) version 9.3. Ethics approval was obtained from
Results
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the Conjoint Health Research Ethics Board at the University of Calgary.
In total, 456,263 patients (mean age 57.6 years, 50.6% men) with newly diagnosed hypertension were identified in fiscal years 1998 to 2008, of whom the majority (62.5%) had no comorbidities at the time of their hypertension diagnosis (Table 1). Patients with newly diagnosed hypertension and no comorbidity were more likely to be younger, have a higher income and be urban dwellers (Table 1).
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The vast majority of our cohort was diagnosed with hypertension on the basis of 2 outpatient clinic visits (90.1%). Within our cohort, in the year preceding diagnosis of hypertension, 7,386,681 physician claims
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were submitted (Figure 1). Of those, 4,933,038 were excluded because they were for diagnostic and therapeutic services, in-patient services, day surgical procedures or emergency department visits. An additional 220,346 claims (3.0% of the total number of claims) were excluded because the service
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provider specialty was an internal medicine specialist in an outpatient clinic rather than a PCP (i.e. it was a visit with general internal medicine, cardiology, nephrology, etc.). The remaining 2,233,297 out-
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patient PCP claims were included in the analysis in the year preceding hypertension diagnosis. Similarly, in the year following diagnosis with hypertension, 8,888,886 physician claims were submitted. Of those, 5,499,698 were excluded because they were for diagnostic and therapeutic services, in-patient services, day surgical procedures or emergency department visits and 271,710 were
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excluded (3.1% of the total number of claims) as they were internal medicine specialist outpatient visits. The remaining 3,389,188 out-patient PCP claims in the year following diagnosis were included. Of note, only 4228 of our incident hypertension cohort (0.93%) were seen solely by an internal
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medicine specialist as an outpatient in the year after diagnosis and had no PCP visits. More than 88% of all patients had seen a PCP at least once in the year prior to their diagnosis of
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hypertension (Table S1 in Supplementary Materials), and the frequency of PCP visits for any indication increased after the diagnosis of hypertension in all four comorbidity-defined subgroups. As expected, the mean number of visits among those with comorbidities was higher than those with no comorbidities both before and after the diagnosis of hypertension. Generally, the mean number of visits was higher among females than males and among older age groups than younger age groups, but utilization patterns did not vary substantially across rural versus urban regions or by socioeconomic status. The
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majority of the increase in PCP visits observed from the year preceding diagnosis to the year following diagnosis was accounted for by hypertension-related visits (Table S1 in Supplementary Materials). The absolute (and relative) increase was greater in those with no comorbidities compared to those with at
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least one comorbidity. Individuals under 35 years of age, males, and those from lower income quintile had higher percentages of patients with no PCP visits (Table S2 in Supplementary Materials).
However, it should be noted that even in these “under-served” subgroups, more than 90% of patients
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had at least one PCP visit in the year after the diagnosis of hypertension.
The mean number of PCP visits before hypertension diagnosis remained stable from 1998-2008
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across all comorbidity subgroups (Figure 2, p-values: no comorbidity 0.47, vascular risk-related 0.93, unrelated 0.41). The adjusted model included age, sex, urban/rural dwelling and income quintile. However, the adjusted mean number of visits after diagnosis appeared to decline over time (Figure 3) with a statistically significant decline amongst those with no comorbidities (p-value 0.01), vascular
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risk-related comorbidities (p-value 75 yrs. Income quintile (mean, 95% CI) 1 (lowest) 2 3 4 5 (highest) Missing Region of residence (mean, 95% CI)) Rural Urban Missing
7.99 (7.95-8.03)
1.20 (1.18-1.21)
6.76 (6.72-6.81)
8.24 (8.19-8.29)
1.77 (1.75-1.79)
4.54 (4.51-4.56) 3.34 (3.32-3.35)
6.78 (6.75-6.81) 5.51 (5.48-5.53)
2.35 (2.33-2.37) 2.22 (2.2-2.24)
7.05 (6.98-7.13) 6.05 (5.99-6.11)
8.68 (8.6-8.76) 7.96 (7.89-8.03)
1.41 (1.36-1.47) 1.22 (1.18-1.27)
7.38 (7.31-7.45) 5.95 (5.89-6.01)
8.88 (8.81-8.96) 7.54 (7.47-7.61)
2.02 (1.97-2.06) 1.92 (1.88-1.97)
3.91 (3.86-3.96) 3.8 (3.76-3.83) 3.71 (3.69-3.74) 3.75 (3.73-3.78) 3.95 (3.92-3.99) 4.24 (4.19-4.30)
5.74 (5.68-5.80) 5.95 (5.91-5.99) 5.97 (5.94-6.00) 6.05 (6.01-6.08) 6.37 (6.32-6.41) 6.64 (6.57-6.70)
1.94 (1.91-1.98) 2.39 (2.36-2.42) 2.45 (2.43-2.47) 2.38 (2.36-2.4) 2.37 (2.35-2.40) 2.22 (2.19-2.26)
6.22 (6.00-6.45) 6.53 (6.39-6.67) 6.30 (6.21-6.39) 6.54 (6.45-6.62) 6.81 (6.72-6.89) 6.83 (6.75-6.91)
7.61 (7.37-7.86) 8.46 (8.30-8.62) 8.42 (8.32-8.52) 8.59 (8.5-8.68) 8.68 (8.59-8.77) 8.17 (8.08-8.26)
1.12 (1.03-1.21) 1.47 (1.4-1.55) 1.47 (1.41-1.53) 1.50 (1.44-1.56) 1.44 (1.39-1.5) 1.00 (0.96-1.04)
6.99 (6.80-7.17) 7.18 (7.06-7.3) 6.67 (6.58-6.76) 6.36 (6.27-6.44) 6.38 (6.29-6.46) 6.25 (6.15-6.35)
8.41 (8.21-8.61) 8.69 (8.55-8.82) 8.33 (8.24-8.43) 8.05 (7.96-8.15) 8.04 (7.95-8.15) 7.61 (7.5-7.72)
1.85 (1.77-1.94) 2.16 (2.09-2.23) 2.21 (2.15-2.26) 2.09 (2.04-2.14) 2.02 (1.97-2.08) 1.56 (1.52-1.61)
4.00 (3.97-4.04) 3.89 (3.86-3.92) 3.97 (3.93-4.00) 3.97 (3.94-4.00) 3.78 (3.75-3.82) 3.74 (3.69-3.79)
6.23 (6.18-6.27) 6.12 (6.08-6.16) 6.20 (6.16-6.24) 6.24 (6.20-6.28) 5.90 (5.86-5.94) 5.99 (5.93-6.06)
2.29 (2.26-2.31) 2.29 (2.27-2.32) 2.30 (2.28-2.33) 2.32 (2.29-2.35) 2.23 (2.21-2.26) 2.29 (2.25-2.33)
6.82 (6.73-6.91) 6.68 (6.59-6.78) 6.67 (6.58-6.77) 6.49 (6.39-6.59) 6.22 (6.12-6.33) 6.33 (6.17-6.49)
8.47 (8.38-8.57) 8.43 (8.33-8.53) 8.56 (8.45-8.67) 8.31 (8.2-8.42) 8.07 (7.95-8.18) 8.06 (7.88-8.23)
1.25 (1.20-1.3) 1.30 (1.25-1.36) 1.34 (1.29-1.4) 1.37 (1.31-1.43) 1.35 (1.29-1.41) 1.29 (1.22-1.36)
7.06 (6.96-7.15) 6.77 (6.67-6.86) 6.75 (6.65-6.84) 6.70 (6.60-6.80) 6.14 (6.04-6.24) 6.40 (6.24-6.56)
8.62 (8.51-8.72) 8.36 (8.26-8.47) 8.44 (8.33-8.55) 8.25 (8.14-8.36) 7.65 (7.54-7.76) 7.82 (7.64-7.99)
1.93 (1.88-1.98) 1.95 (1.90-2.01) 2.01 (1.96-2.07) 2.03 (1.97-2.09) 2.00 (1.95-2.06) 1.89 (1.81-1.97)
3.75 (3.72-3.79) 3.96 (3.95-3.98) 3.74 (3.69-3.79)
5.83 (5.79-5.87) 6.21 (6.19-6.23) 6.00 (5.93-6.06)
2.22 (2.19-2.25) 2.30 (2.29-2.32) 2.29 (2.25-2.33)
6.77 (6.68-6.87) 6.57 (6.51-6.63) 6.33 (6.17-6.49)
8.52 (8.42-8.63) 8.35 (8.29-8.42) 8.06 (7.89-8.24)
1.30 (1.25-1.35) 1.33 (1.28-1.38) 1.29 (1.22-1.37)
6.74 (6.65-6.84) 6.71 (6.66-6.76) 6.40 (6.24-6.57)
8.35 (8.25-8.46) 8.28 (8.22-8.34) 7.82 (7.64-8.00)
1.96 (1.91-2.01) 1.99 (1.95-2.03) 1.89 (1.81-1.97)
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6.45 (6.41-6.49)
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Age (mean, 95% CI) < 35 yrs.
2.08 (2.07-2.09)
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Male
58.9 (58.6-59.3)
6.15 (6.13-6.17)
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Sex (mean, 95% CI) Female
HTN-r*
3.95 (3.93-3.97)
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Number of visits (mean, 95% CI)
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Table S1: Utilization of primary care physicians visits in the year preceding and following hypertension diagnosis, by comorbidity status Comorbidity status None Vascular related Unrelated Variable (n=285599) (n=96467) (n=74197) Before After HTN-r* Before After HTN-r* Before After 86.9 95.0 66.9 90.4 91.7 44.3 94.7 95.7 Percent utilizing a PCP (86.8-87.1) (94.9-95.1) (66.8-67.1) (90.2-90.6) (91.5-91.9) (44.0-44.6) (94.5-94.9) (95.5-95.8) (%, 95% CI)
*Hypertension-related PCP visits
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Table S2: Percent utilizing a PCP in the year preceding and following hypertension diagnosis, by comorbidity status Comorbidity status None Vascular related Unrelated Variable (n=285599) (n=96467) (n=74197) Before After HTN-r* Before After HTN-r* Before After HTN-r* 86.9 95.0 66.9 90.4 91.7 44.3 94.7 95.7 58.9 Overall (%) Sex (%) Female 89.8 96.5 68.1 91.2 89.7 44.4 95.7 96.2 59.7 Male 82.2 93.1 65.3 88.7 91.6 43.5 92.8 94.4 57.5 Age (%) < 35 yrs. 83.8 91.9 56.5 84.3 89.3 37.4 94.5 95.9 53.4 35-45 yrs. 84.4 93.5 66.1 86.9 94.0 45.9 95.3 96.5 60.5 45-55 yrs. 85.3 94.8 68.6 88.3 95.1 47.4 94.9 96.6 62.4 55-65yrs. 86.5 95.5 76.7 89.8 94.4 47.9 94.8 96.4 61.4 65-75 yrs. 88.1 96.1 67.8 91.4 92.8 47.0 94.5 96.0 59.6 > 75 yrs. 88.4 95.7 65.3 89.8 83.3 36.4 92.0 90.3 48.5 Income quintile (%) 1 (lowest) 84.8 94.4 66.0 88.6 89.0 41.2 93.4 94.4 56.6 2 85.3 94.9 66.8 89.7 91.0 43.7 94.0 95.0 58.5 3 86.1 94.9 66.7 90.5 91.2 44.5 94.4 95.8 59.6 4 86.8 95.0 67.4 91.0 92.1 46.2 95.2 96.3 60.2 5 (highest) 87.1 95.0 67.0 90.2 92.0 45.7 95.3 96.2 60.6 Missing 85.3 94.5 66.2 87.6 89.7 41.2 94.0 94.7 55.0 Region of residence (%) Rural 84.4 94.1 65.8 89.8 91.7 44.1 93.5 95.5 58.7 Urban 86.4 95.0 67.0 89.9 90.6 43.9 94.6 95.4 59.0 Missing 85.3 94.5 66.2 87.6 89.7 41.2 94.0 94.7 55.0 *Hypertension-related PCP visits
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S0828-282X(14)00191-3
DOI:
10.1016/j.cjca.2014.03.033
Reference:
CJCA 1165
To appear in:
Canadian Journal of Cardiology
Received Date: 28 October 2013 Revised Date:
26 March 2014
Accepted Date: 26 March 2014
Please cite this article as: Clement FM, Chen G, Khan N, Tu K, Campbell NRC, Smith M, Quan H, Hemmelgarn BR, McAlister FA, , Primary care physician visits by patients with incident hypertension, Canadian Journal of Cardiology (2014), doi: 10.1016/j.cjca.2014.03.033. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Primary care physician visits by patients with incident hypertension
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Fiona M Clement, PhDa,b, Guanmin Chen MD, PhDa, b, Nadia Khan, MD, MScc, Karen Tu, MD, MScd, Norm R.C. Campbell, MDa, e, f, Mark Smith, MScg, Hude Quan, MD, PhDa, b, Brenda R. Hemmelgarn, MD, PhDa, b,e, Finlay A. McAlister, MD, MSch for the Hypertension Outcome and Surveillance Team a
Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada Institute of Public Health, University of Calgary, Calgary, Alberta, Canada c Division of General Internal Medicine, University of British Columbia, British Columbia, Vancouver, Canada d Department of Family and Community Medicine, University of Toronto/Institute for Clinical Evaluative Sciences (ICES), Toronto, Ontario, Canada e Department of Medicine, University of Calgary, Calgary, Alberta, Canada f Department of Pharmacology and Therapeutics, University of Calgary, Calgary, Alberta, Canada g Manitoba Centre for Health Policy, University of Manitoba, Winnipeg, Manitoba, Canada h Division of General Internal Medicine, University of Alberta, Edmonton, Ontario, Canada
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Short Title: PCP use among incident hypertensives Corresponding Author:
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Dr. Fiona Clement GD3#18, TRW Building University of Calgary 3280 Hospital Dr NW, Calgary, AB T2N 4Z6 Phone: 403-210-9373 Email: [email protected]
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Word Count: 2645 words, 3 tables, 3 figures, 1 etable
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Brief Summary The study objective is to compare primary care physician (PCP) visits among patients with incident hypertension with and without other comorbidities. Three categories of comorbidities were defined: 1)
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none, 2) vascular risk-related and 3) unrelated. The frequency of PCP visits was high before (88% at least one visit, mean 4.94 per annum) and after (94% at least one visit, mean 6.88 per annum) diagnosis
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of hypertension.
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Abstract (249 words) Background: Access to primary care physicians (PCP) improves health outcomes among patients with hypertension. The study objective is to compare PCP use among patients with incident hypertension
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with and without comorbidities.
Methods: Newly diagnosed hypertensives between April 1, 1998 and March 31, 2009 were identified using Alberta administrative databases. Three comorbidity subgroups were defined: 1) none, 2)
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vascular risk-related, and 3) unrelated. The number of PCP visits was calculated using zero-inflation Poisson regression, with time trends compared using the chi-squared test. A Cox model was used to
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assess the association between PCP utilization and clinical outcomes.
Results: Of 456,263 newly diagnosed hypertensives (mean age 57.6 years, 50.6% men, 62.5% no comorbidity), 88% had seen a PCP in the year pre-diagnosis and 94% in the year following. Compared to pre-diagnosis, the mean number of PCP visits increased after diagnosis (none 3.95 vs.6.15; vascular
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risk-related 6.45 vs. 7.99; and unrelated 6.76 vs.8.24). Over the study period the frequency of prediagnosis PCP visits was constant; there was a statistically significant decline in the adjusted mean number of visits after diagnosis. Those with higher PCP use were less likely to die but more likely to be
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hospitalized regardless of comorbidity.
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Conclusions: The frequency of PCP visits was high before and after diagnosis. Increased PCP use was associated with a lower risk of death, however, it does increase the costs of caring for patients with hypertension, therefore future studies are required to determine the optimal utilization level to achieve cost-effective use of PCP resources.
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Introduction Hypertension is one of the most common chronic conditions world-wide (1) affecting 23% of
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the Canadian adult population (2). It is an important modifiable risk factor for cardiovascular disease and the most common attributable cause for mortality in the world (3;4). More patients visit primary care physicians (PCPs) and receive prescriptions for the treatment of hypertension than any other
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medical disorder (5;6), with more than 4 million prescriptions for antihypertensive medications written every month in Canada (7). The cost in high income countries’ health care systems to manage patients
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with hypertension and related complications is estimated to consume 10% of all health care spending (8;9).
A better understanding of health care resource use for hypertension will enable targeted strategies to be developed to facilitate more cost-effective care. Even small changes in healthcare costs
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to manage hypertension will have a large overall impact given the high prevalence of hypertension in Canada. With an aging Canadian population it is expected that there will be an increase in the burden of hypertension related chronic illnesses, multiple comorbidities, and disability as well as the demand
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for health care services (10). Hypertension Canada, policy makers and health care professionals have made extensive efforts to improve hypertension detection and management through development of
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ongoing national knowledge translation strategies (11;12). Currently in Canada there are no mechanisms in place to monitor hypertension management, hypertension-related outcomes, and health care resource implications. Inefficient care will lead to a significant burden to publically funded health care systems through either inefficient management, or excess hypertension attributable end-organ complications, with attendant implications on health and health care costs. Thus, at a time of unprecedented pressure on our health care system, health care
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leaders are driven to reduce waste and inefficiency. Identifying inefficiencies and factors associated with clinical care gaps in hypertension management is imperative for designing policy and intervention
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programs to close care gaps. To our best knowledge, no studies have documented the pattern of PCP visits after a new diagnosis of hypertension in the universal healthcare system in Canada, and whether the frequency of
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these visits varies by the presence of other comorbid conditions and socioeconomic factors. Given the prevalence and importance of hypertension in the outpatient setting, particularly primary care physician
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offices, this study focused on evaluating the PCP utilization patterns among patients with incident hypertension with and without other comorbidities. Methods Data Sources
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Administrative health databases from Alberta were linked using an anonymized unique personal identifier. The study databases included provincial health insurance registries, hospital discharge abstracts and physician billing claims. The Alberta insurance registry contains demographic
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information including date of birth, sex, and mailing address for all residents of the province eligible to receive health services. Discharge abstracts contain clinical information for all hospitalized patients
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with up to 25 diagnosis codes recorded for each hospitalization using the International Classification of Disease (ICD), 9th Revision (i.e., ICD-9), ICD-9 Clinical Modification (ICD-9-CM) prior to April 2002 or ICD-10 Canadian Modification (i.e., ICD-10-CA) after April 2002 (13-15). Physician billing claims contains fee-for-service billing information that includes a unique physician identifier and ICD-9 codes for services provided. At least one ICD-9 code, and up to three are recorded, corresponding to the primary reasons for each physician visit. Physicians submit claims for payment or reporting services to
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provincial government insurance programs. The physician claims capture outpatient physician services and the majority of inpatient physician services and each claim records the billing physicians’ specialist
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type. Study Population
We defined a cohort of patients newly diagnosed with hypertension between April 1 1998 and
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March 31, 2009 (fiscal years 1998-2008). Hypertension cases were identified using a previously validated case definition for Canadian hospital discharge and physician claims administrative databases
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which was 75% sensitive and 94% specific, with positive predictive value of 81%, when evaluated in the Alberta datasets in the same timeframe as this study (16;17). The first date a hypertension code was specified was defined as the date of diagnosis. We excluded patients with an index date between April 1 1994 and March 31 1997 (i.e., 3 year washout period) to focus on patients with incident
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hypertension. Outcomes
The primary outcome was the mean number of out-patient PCP visits in the year following their
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diagnosis of hypertension. As the majority of patients with hypertension are managed in the
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community by a PCP (Figure 1), only outpatient PCP services were analyzed in this study. Hypertension-related PCP visits and the number of patients with no visits were secondary outcomes. Hypertension-related PCP visits were identified using ICD-9 codes 401.x, 402.x, 403.x, 404.x, or 405.x. Patients with no PCP outpatient visits in the year following diagnosis were considered to have no PCP utilization. To assess the association between PCP utilization and outcomes, death, all cause hospitalization, cardiovascular-specific hospitalization (ICD codes G45, G46, I60 - I69, H340, I43, I50, I099, I110, I130, I132, I255, I420, I425 - I429, P290, I21, I22, I252 as the most responsible diagnosis) 6
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and hypertension-specific hospitalization (ICD codes 401.x, 402.x, 403.x, 404.x, or 405.x as the most responsible diagnosis) were considered. All outcomes were defined 1 year following hypertension
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diagnosis. Exposure Variables
Comorbidity status, defined using the Charlson comorbidities, was the exposure variable. All
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comorbidities were derived from validated ICD9/ICD10 algorithms using both the hospital discharge abstract data and the physician claims database for the three years prior to hypertension diagnosis
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(18;19). Three categories of comorbidity were considered: 1) no comorbidity, 2) vascular risk-related comorbidity (myocardial infarction, congestive heart failure, peripheral vascular disease, and cerebrovascular disease, diabetes with and without complications and renal disease) and 3) unrelated comorbidity (ie. unrelated to vascular risk including dementia, chronic pulmonary obstructive disease,
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connective tissue disease, rheumatic disease, peptic ulcer disease, paraplegia/hemiplegia, liver disease, cancer/metastatic carcinoma and AIDS/HIV). In the analysis considering clinical outcomes, PCP utilization was the exposure variable, and categorized based on utilization within other healthcare
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Independent Variables
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settings (20) as ≤ 2 visits per year, 2-5 visits per year and ≥ 5 visits per year.
Age and sex at index date of hypertension diagnosis were defined using the registry data. Age was categorized into 6 groups: under 35, 35-45, 45-55, 55-65, 65-75 and over 75 years of age. Median income quintile was assigned using 2001 Statistics Canada Census data and each patient’s postal code forward sortation area. Statistical Analysis
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Baseline characteristics of patients with incident hypertension were analyzed descriptively. To provide a baseline measure of utilization, all outcomes were calculated for both the year preceding and following hypertension diagnosis. The number of PCP visits in the year preceding and the year
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following diagnosis was estimated using zero-inflation Poisson regression to account for the overdispersion due to excessive zeros counts. If the Poisson assumption that variance is equal to the mean was not met, negative binominal regression was used. If hypertension was defined using physician
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claims, the 2 visits required to meet the definition of hypertension were not included in estimates of the mean number of visits. Both crude and adjusted means are reported. The adjusted model included age
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group, sex, income quintile, rural/urban, and year of diagnosis. To assess if utilization patterns have changed over time, the mean number of PCP visits was calculated by year of diagnosis. A chi-squared test for trend was completed for each comorbidity group over time. A proportional hazard Cox model was completed to assess the association between PCP utilization and clinical outcomes including death,
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and all cause-, cardiovascular- and hypertension-specific hospitalization. Due to the time-dependent nature of PCP exposure, only adjusted analyses are considered. A time-dependent variable was included to account for the relationship between PCP utilization and exposure time. All analyses were
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adjusted for age, sex, income quintile, rural/urban and year of diagnosis. The statistical analyses were conducted using Statistical Analysis software (SAS) version 9.3. Ethics approval was obtained from
Results
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the Conjoint Health Research Ethics Board at the University of Calgary.
In total, 456,263 patients (mean age 57.6 years, 50.6% men) with newly diagnosed hypertension were identified in fiscal years 1998 to 2008, of whom the majority (62.5%) had no comorbidities at the time of their hypertension diagnosis (Table 1). Patients with newly diagnosed hypertension and no comorbidity were more likely to be younger, have a higher income and be urban dwellers (Table 1).
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The vast majority of our cohort was diagnosed with hypertension on the basis of 2 outpatient clinic visits (90.1%). Within our cohort, in the year preceding diagnosis of hypertension, 7,386,681 physician claims
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were submitted (Figure 1). Of those, 4,933,038 were excluded because they were for diagnostic and therapeutic services, in-patient services, day surgical procedures or emergency department visits. An additional 220,346 claims (3.0% of the total number of claims) were excluded because the service
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provider specialty was an internal medicine specialist in an outpatient clinic rather than a PCP (i.e. it was a visit with general internal medicine, cardiology, nephrology, etc.). The remaining 2,233,297 out-
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patient PCP claims were included in the analysis in the year preceding hypertension diagnosis. Similarly, in the year following diagnosis with hypertension, 8,888,886 physician claims were submitted. Of those, 5,499,698 were excluded because they were for diagnostic and therapeutic services, in-patient services, day surgical procedures or emergency department visits and 271,710 were
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excluded (3.1% of the total number of claims) as they were internal medicine specialist outpatient visits. The remaining 3,389,188 out-patient PCP claims in the year following diagnosis were included. Of note, only 4228 of our incident hypertension cohort (0.93%) were seen solely by an internal
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medicine specialist as an outpatient in the year after diagnosis and had no PCP visits. More than 88% of all patients had seen a PCP at least once in the year prior to their diagnosis of
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hypertension (Table S1 in Supplementary Materials), and the frequency of PCP visits for any indication increased after the diagnosis of hypertension in all four comorbidity-defined subgroups. As expected, the mean number of visits among those with comorbidities was higher than those with no comorbidities both before and after the diagnosis of hypertension. Generally, the mean number of visits was higher among females than males and among older age groups than younger age groups, but utilization patterns did not vary substantially across rural versus urban regions or by socioeconomic status. The
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majority of the increase in PCP visits observed from the year preceding diagnosis to the year following diagnosis was accounted for by hypertension-related visits (Table S1 in Supplementary Materials). The absolute (and relative) increase was greater in those with no comorbidities compared to those with at
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least one comorbidity. Individuals under 35 years of age, males, and those from lower income quintile had higher percentages of patients with no PCP visits (Table S2 in Supplementary Materials).
However, it should be noted that even in these “under-served” subgroups, more than 90% of patients
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had at least one PCP visit in the year after the diagnosis of hypertension.
The mean number of PCP visits before hypertension diagnosis remained stable from 1998-2008
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across all comorbidity subgroups (Figure 2, p-values: no comorbidity 0.47, vascular risk-related 0.93, unrelated 0.41). The adjusted model included age, sex, urban/rural dwelling and income quintile. However, the adjusted mean number of visits after diagnosis appeared to decline over time (Figure 3) with a statistically significant decline amongst those with no comorbidities (p-value 0.01), vascular
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risk-related comorbidities (p-value 75 yrs. Income quintile (mean, 95% CI) 1 (lowest) 2 3 4 5 (highest) Missing Region of residence (mean, 95% CI)) Rural Urban Missing
7.99 (7.95-8.03)
1.20 (1.18-1.21)
6.76 (6.72-6.81)
8.24 (8.19-8.29)
1.77 (1.75-1.79)
4.54 (4.51-4.56) 3.34 (3.32-3.35)
6.78 (6.75-6.81) 5.51 (5.48-5.53)
2.35 (2.33-2.37) 2.22 (2.2-2.24)
7.05 (6.98-7.13) 6.05 (5.99-6.11)
8.68 (8.6-8.76) 7.96 (7.89-8.03)
1.41 (1.36-1.47) 1.22 (1.18-1.27)
7.38 (7.31-7.45) 5.95 (5.89-6.01)
8.88 (8.81-8.96) 7.54 (7.47-7.61)
2.02 (1.97-2.06) 1.92 (1.88-1.97)
3.91 (3.86-3.96) 3.8 (3.76-3.83) 3.71 (3.69-3.74) 3.75 (3.73-3.78) 3.95 (3.92-3.99) 4.24 (4.19-4.30)
5.74 (5.68-5.80) 5.95 (5.91-5.99) 5.97 (5.94-6.00) 6.05 (6.01-6.08) 6.37 (6.32-6.41) 6.64 (6.57-6.70)
1.94 (1.91-1.98) 2.39 (2.36-2.42) 2.45 (2.43-2.47) 2.38 (2.36-2.4) 2.37 (2.35-2.40) 2.22 (2.19-2.26)
6.22 (6.00-6.45) 6.53 (6.39-6.67) 6.30 (6.21-6.39) 6.54 (6.45-6.62) 6.81 (6.72-6.89) 6.83 (6.75-6.91)
7.61 (7.37-7.86) 8.46 (8.30-8.62) 8.42 (8.32-8.52) 8.59 (8.5-8.68) 8.68 (8.59-8.77) 8.17 (8.08-8.26)
1.12 (1.03-1.21) 1.47 (1.4-1.55) 1.47 (1.41-1.53) 1.50 (1.44-1.56) 1.44 (1.39-1.5) 1.00 (0.96-1.04)
6.99 (6.80-7.17) 7.18 (7.06-7.3) 6.67 (6.58-6.76) 6.36 (6.27-6.44) 6.38 (6.29-6.46) 6.25 (6.15-6.35)
8.41 (8.21-8.61) 8.69 (8.55-8.82) 8.33 (8.24-8.43) 8.05 (7.96-8.15) 8.04 (7.95-8.15) 7.61 (7.5-7.72)
1.85 (1.77-1.94) 2.16 (2.09-2.23) 2.21 (2.15-2.26) 2.09 (2.04-2.14) 2.02 (1.97-2.08) 1.56 (1.52-1.61)
4.00 (3.97-4.04) 3.89 (3.86-3.92) 3.97 (3.93-4.00) 3.97 (3.94-4.00) 3.78 (3.75-3.82) 3.74 (3.69-3.79)
6.23 (6.18-6.27) 6.12 (6.08-6.16) 6.20 (6.16-6.24) 6.24 (6.20-6.28) 5.90 (5.86-5.94) 5.99 (5.93-6.06)
2.29 (2.26-2.31) 2.29 (2.27-2.32) 2.30 (2.28-2.33) 2.32 (2.29-2.35) 2.23 (2.21-2.26) 2.29 (2.25-2.33)
6.82 (6.73-6.91) 6.68 (6.59-6.78) 6.67 (6.58-6.77) 6.49 (6.39-6.59) 6.22 (6.12-6.33) 6.33 (6.17-6.49)
8.47 (8.38-8.57) 8.43 (8.33-8.53) 8.56 (8.45-8.67) 8.31 (8.2-8.42) 8.07 (7.95-8.18) 8.06 (7.88-8.23)
1.25 (1.20-1.3) 1.30 (1.25-1.36) 1.34 (1.29-1.4) 1.37 (1.31-1.43) 1.35 (1.29-1.41) 1.29 (1.22-1.36)
7.06 (6.96-7.15) 6.77 (6.67-6.86) 6.75 (6.65-6.84) 6.70 (6.60-6.80) 6.14 (6.04-6.24) 6.40 (6.24-6.56)
8.62 (8.51-8.72) 8.36 (8.26-8.47) 8.44 (8.33-8.55) 8.25 (8.14-8.36) 7.65 (7.54-7.76) 7.82 (7.64-7.99)
1.93 (1.88-1.98) 1.95 (1.90-2.01) 2.01 (1.96-2.07) 2.03 (1.97-2.09) 2.00 (1.95-2.06) 1.89 (1.81-1.97)
3.75 (3.72-3.79) 3.96 (3.95-3.98) 3.74 (3.69-3.79)
5.83 (5.79-5.87) 6.21 (6.19-6.23) 6.00 (5.93-6.06)
2.22 (2.19-2.25) 2.30 (2.29-2.32) 2.29 (2.25-2.33)
6.77 (6.68-6.87) 6.57 (6.51-6.63) 6.33 (6.17-6.49)
8.52 (8.42-8.63) 8.35 (8.29-8.42) 8.06 (7.89-8.24)
1.30 (1.25-1.35) 1.33 (1.28-1.38) 1.29 (1.22-1.37)
6.74 (6.65-6.84) 6.71 (6.66-6.76) 6.40 (6.24-6.57)
8.35 (8.25-8.46) 8.28 (8.22-8.34) 7.82 (7.64-8.00)
1.96 (1.91-2.01) 1.99 (1.95-2.03) 1.89 (1.81-1.97)
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6.45 (6.41-6.49)
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Age (mean, 95% CI) < 35 yrs.
2.08 (2.07-2.09)
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Male
58.9 (58.6-59.3)
6.15 (6.13-6.17)
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Sex (mean, 95% CI) Female
HTN-r*
3.95 (3.93-3.97)
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Number of visits (mean, 95% CI)
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Table S1: Utilization of primary care physicians visits in the year preceding and following hypertension diagnosis, by comorbidity status Comorbidity status None Vascular related Unrelated Variable (n=285599) (n=96467) (n=74197) Before After HTN-r* Before After HTN-r* Before After 86.9 95.0 66.9 90.4 91.7 44.3 94.7 95.7 Percent utilizing a PCP (86.8-87.1) (94.9-95.1) (66.8-67.1) (90.2-90.6) (91.5-91.9) (44.0-44.6) (94.5-94.9) (95.5-95.8) (%, 95% CI)
*Hypertension-related PCP visits
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Table S2: Percent utilizing a PCP in the year preceding and following hypertension diagnosis, by comorbidity status Comorbidity status None Vascular related Unrelated Variable (n=285599) (n=96467) (n=74197) Before After HTN-r* Before After HTN-r* Before After HTN-r* 86.9 95.0 66.9 90.4 91.7 44.3 94.7 95.7 58.9 Overall (%) Sex (%) Female 89.8 96.5 68.1 91.2 89.7 44.4 95.7 96.2 59.7 Male 82.2 93.1 65.3 88.7 91.6 43.5 92.8 94.4 57.5 Age (%) < 35 yrs. 83.8 91.9 56.5 84.3 89.3 37.4 94.5 95.9 53.4 35-45 yrs. 84.4 93.5 66.1 86.9 94.0 45.9 95.3 96.5 60.5 45-55 yrs. 85.3 94.8 68.6 88.3 95.1 47.4 94.9 96.6 62.4 55-65yrs. 86.5 95.5 76.7 89.8 94.4 47.9 94.8 96.4 61.4 65-75 yrs. 88.1 96.1 67.8 91.4 92.8 47.0 94.5 96.0 59.6 > 75 yrs. 88.4 95.7 65.3 89.8 83.3 36.4 92.0 90.3 48.5 Income quintile (%) 1 (lowest) 84.8 94.4 66.0 88.6 89.0 41.2 93.4 94.4 56.6 2 85.3 94.9 66.8 89.7 91.0 43.7 94.0 95.0 58.5 3 86.1 94.9 66.7 90.5 91.2 44.5 94.4 95.8 59.6 4 86.8 95.0 67.4 91.0 92.1 46.2 95.2 96.3 60.2 5 (highest) 87.1 95.0 67.0 90.2 92.0 45.7 95.3 96.2 60.6 Missing 85.3 94.5 66.2 87.6 89.7 41.2 94.0 94.7 55.0 Region of residence (%) Rural 84.4 94.1 65.8 89.8 91.7 44.1 93.5 95.5 58.7 Urban 86.4 95.0 67.0 89.9 90.6 43.9 94.6 95.4 59.0 Missing 85.3 94.5 66.2 87.6 89.7 41.2 94.0 94.7 55.0 *Hypertension-related PCP visits
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