Epidemiology of constipation (EPOC) study in the United States: Relation of clinical subtypes to sociodemographic features

OBJECTIVE: Constipation is a common heterogeneous condition, possibly encom passing different clinical subtypes. Little is known about the comparative epidemiology of constipation subtypes. This study was conducted to estimate the prevalence of constipation subtypes and determine whether subtypes dif fer by sociodemographic factors. METHODS: Between June and September 1997, a telephone interview was conduct ed with individuals about their bowel habits in the preceding 3 months. Sur vey data on 15 constipation-related symptoms were used to identify individu als who met prespecified symptom criteria for the following mutually exclus ive subgroups: functional constipation, irritable bowel syndrome (IBS), out let obstruction or delay (outlet), both IBS and outlet (IBS-outlet), and fr equent laxative users (i.e., at least every other day). A total of 10,018 e ligible individuals in the United States 18 yr of age or older completed th e interview. Test-retest reliability of reporting symptoms was assessed in a separate national survey. The Spearman's correlation coefficient for repo rting symptoms ranged from 0.54 to 0.83; all but three symptoms had correla tions above 0.68. RESULTS: The overall prevalence of constipation was 14.7%. By subtype, prev alence was 4.6% for functional, 2.1% for IBS, 4.6% for outlet, and 3.4% for IBS-outlet. An additional 1.8% of respondents reported laxative use at lea st every other day. Outlet was the most common subtype among women, whereas functional constipation was the most common subtype among men. The gender ratio varied by subtype, with elevated ratios for outlet (F/M = 1.65) and I BS-outlet (F/M = 2.27) subtypes. The age pattern differed among each of the four subtypes. Prevalence of functional subtype decreased with increasing age. In contrast, outlet subtype did not seem to vary by age, and IBS (both men and women) and IBS-outlet (women only) subtypes increased to age 35 yr and declined thereafter. Prevalence of functional constipation increased w ith increasing education. Outlet type was more common in nonwhites compared to whites. Finally, 45% of individuals with constipation reported having t he condition for 5 yr or more. CONCLUSIONS: Constipation is a heterogeneous condition. Differences in epid emiological profile by age, sex ratio, and relation to other sociodemograph ical factors support the distinction of two and possibly more symptom-based subtypes. (Am J Gastroenterol 1999;94:3530-3540. (C) 1999 by Am. Coll. of Gastroenterology).