Demographic and Dietary Determinants of Constipation in the US Population ROBERT S. SANDLER, MD, MPH, MATTHEW C. JORDAN, MS,

AND

BRENT J. SHELTON, BS

Abstract: We investigated the association between self-reported constipation and several demographic and dietary variables in 15,014 men and women 12-74 years of age examined between 1971-75 during the first Health and Nutrition Examination Survey. Overall, 12.8 percent reported constipation. Self-reported constipation correlated poorly with stool frequency. Nine percent of those with daily stools and 30.6 percent of those with four to six stools/week, reported constipation. Constipation was more frequent in Blacks (17.3 percent), women (18.2 percent), and those over age 60 (23.3 percent);

after adjusting for age, sex, and race it was more prevalent in those with daily inactivity, little leisure exercise, low income, and poor education. Constipated subjects reported lower consumption of cheese, dry beans and peas, milk, meat and poultry, beverages (sweetened, carbonated and noncarbonated), and fruits and vegetables. They reported higher consumption of coffee or tea. They consumed fewer total calories even after controlling for body mass and exercise. (Am J Public Health 1990; 80:185-189.)

Introduction Constipation is a significant problem in the United States with over 330 million dollars spent each year on overthe-counter laxatives.' Our understanding of both the epidemiology and pathophysiology is limited. Studies of constipation are handicapped by lack of a standard definition of the condition. Connell, et al,2 inquired about the bowel habits of 1,055 persons not seeking medical advice in an industrial community. They found that 99.4 percent had three or more bowel movements per week. Based on this work, individuals with fewer than three stools per week are usually considered to be constipated. While physicians and investigators often define constipation by stool frequencies that lie below the usual range, healthy subjects tend to define constipation in terms of function (straining) and stool consistency (hard stools).3 Because of the lack of a standard definition, because bowel habits change with time, and because constipation depends on age and sex, the range of reported prevalence is quite broad. In a group of healthy young adults not seeking health care, Sandler and Drossman found that 7.3 percent reported that they were constipated more than 25 percent of the time.3 When constipation was defined as straining more than 25 percent of the time, Thompson and Heaton found that 10.3 percent of subjects were constipated.4 In a prospective study of 1,064,004 men and women who were surveyed by American Cancer Society volunteers, 18.5 percent of men and 33.7 percent of women reported "constipation."5 Sonnenberg and Koch have recently performed detailed analyses of constipation using data from the National Hospital Discharge Survey, the National Health Interview Survey, the National Ambulatory Medical Care Survey, and the Vital Statistics of the United States.6 Constipation was the most frequent digestive compliant in the United States with an estimated four million people complaining of "frequent constipation." There were over 92,000 annual hospitalizations with constipation listed among the hospital discharge

diagnoses, and 900 deaths from diseases associated with or related to constipation. Using data from the National Disease and Therapeutic Index, the same authors reported 2.5 million physician visits for constipation.7 The data are limited in several ways. Most people with constipation do not visit physicians, are not hospitalized, and do not die. The reliability of the prevalence estimates for chronic constipation based on the National Health Interview Survey are uncertain because one member of the household provided health information for all members of that household. The published reports of constipation have not attempted to link constipation with dietary and lifestyle factors that might be responsible for this symptom. The first National Health and Nutrition Examination Survey (NHANES-I) was conducted by the National Center for Health Statistics between 1971-1975.8 The study involved a nationwide probability sample of 20,749 persons. In addition to detailed socio-demographic information, the survey included data on dietary intake, exercise, and bowel dysfunction. We took advantage of unique data available from the NHANES-I to describe the distribution and determinants of constipation in the United States.

Address reprint requests to Robert S. Sandler, MD, MPH, Associate Professor of Medicine and Epidemiology, Division of Digestive Diseases, CB# 7080, 423 Burnett-Womack Bldg., University of North Carolina, Chapel Hill, NC 27599-7080. Mr. Shelton is a doctoral student in Biostatistics at UNCChapel Hill; Mr. Jordan is a research statistician at the Research Triangle Institute, Research Triangle Park, NC. This paper, submitted to the Journal February 21, 1989, was revised and accepted for publication July 13, 1989. © 1990 American Journal of Public Health 0090-0036/90$1.50

AJPH February 1990, Vol. 80, No. 2

Methods The NHANES-I was a large-scale, multistage probability sample designed to closely reflect the US non-institutionalized civilian population, 1-74 years of age. The design and methodology have been described in detail elsewhere.6 The analyses reported here involve 15,014 Black and White persons older than age 12 at the time of the survey, who completed both an examination and a dietary interview. Constipation, in the present study, was based on responses to the question: "Do you have trouble with your bowels that makes you constipated or gives you diarrhea?" Those who answered "yes-constipated," were defined as having self-reported constipation and were compared to those who responded negatively to the question. Those with diarrhea (621), constipation and diarrhea (73), and those with missing information (72) were excluded. Subjects were also asked: "How often do you usually have a bowel movement?" Stool frequency was coded by the National Center for Health Statistics as less than two stools per week, two to three per week, four to six per week, one per day, and two or more per day. It was not possible to analyze stool frequencies apart from these categories. An alternative definition of constipation was fewer than four stools per 185

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week. No time period for self-reported constipation or stool frequency was specified. Height and body weight were obtained through standardized procedures.6 Body mass index (BMI) was calculated using the formula BMI = weight (kg.)/height (m)2 to provide an index of weight controlled for height. Daily calories were determined using standardized food composition tables applied to foods in each person's 24-hour dietary recall record. Subjects were also asked the frequency with which they consumed a variety of foods with categories chosen to provide reasonably balanced numbers in each category. Race was dichotomized as White or Black. Analyses were performed using the Statistical Analysis System (SAS Institute, Cary, NC). The SESUDAAN program, which takes into account the complex sample design of the survey, was used to compute standardized proportions and standard errors.9 The RTILOGIT program'° was run under SAS to perform logistic regression analyses that took account of the sample weights and sample design. Age, body mass index, and calories were entered into models as continuous variables. Categorical variables were coded as described in the Tables.

Results Overall, 12.8 percent (S.E. 0.48) of the United States population reported constipation (Table 1). Self-reported constipation was more common in Blacks (17.3 percent), women (18.2 percent), and those over age 60 (23.3 percent). When we defined constipation as fewer than four stools per week, constipation was again more common in Blacks and women. The elderly did not consistently report fewer stools. There was poor correlation between the reported stool frequency and self-reported constipation (Table 2). Only 67.8 percent of those with fewer than two stools per week reported constipation. Nine percent of those with daily stools, and 30.6 percent of those with four to six stools per week considered themselves constipated. Of the 180 persons with less than two stools per week, 137 (76 percent) were women, supporting the fact that constipation is more common in women. Self-reported constipation was most prevalent in those with daily inactivity and little recreational exercise with a distinct gradient from the most active to the least active at all ages (Table 3). Those with low income and education were more likely to be constipated within each age category. The effect of marital status was inconsistent. Reported constipa-

TABLE 2-Comparison of Stool Frequency to Self-Reported Constipation

Stool Frequencya

Demographic and dietary determinants of constipation in the US population.

We investigated the association between self-reported constipation and several demographic and dietary variables in 15,014 men and women 12-74 years o...
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