Werth BL, et al. - In this investigation, researchers examined the impact of various definitions on prevalence estimates in the same population and compared the performance of simple definitions with the Rome III criteria. Using five simple definitions of constipation and compared with definitions based on the Rome III criteria, the prevalence of constipation in a large nationally representative sample of community-dwelling adults was estimated. Findings revealed that prevalence estimates for the five simple definitions ranged from 9.4 to 58.9%. On the other hand, prevalence estimates using the Rome III criteria were 24.0% for chronic constipation and 39.6% for sub-chronic constipation. The authors concluded that the definition used within a population to identify constipation has a significant impact on the estimate of prevalence obtained. Compared to the Rome III criteria, simple definitions, commonly used in research, were poorly performed. Where possible, studies estimating constipation population prevalence should use definitions based on the Rome criteria.