THE NATURAL-HISTORY OF PROSTATISM - THE EFFECTS OF NONRESPONSE BIAS

Background. In epidemiological studies, non-response may raise the question of generalizability to the target population. Most investigations have not been able to access data that could provide information about the potential impact of nonresponse bias. Methods. A 55% response rate was realized at baseline for a prospective cohort investigation of the natural history of benign prostatic hyperplasia in Olmsted County, Minnesota, during 1989-1991 (the Olmsted County Study of Urinary Symptoms and Health Status Among Men). This prompted a preliminary study of potential non-response bias among full participants, partial participants and complete non-responders. The medical diagnostic index maintained by the Rochester Epidemiology Project was used to ascertain the prevalence of specific conditions in the 9 years prior to study inception. Results. The age-adjusted period prevalence rate for benign prostatic hyperplasia (%) was 9.6 (95% confidence interval [CI] : 8.1-11.0) for full participants, 8.2 (95% CI : 5.8-10.6) for partial participants and 5.3 (95% CI : 3.6-6.9) for complete non-responders. Other urologic diagnoses followed the same pattern. However, age-adjusted prevalence rates for general medical examination history and major non-urologic morbidities were decidedly similar across response groups. Conclusions. These data suggest response may have been driven, in part, by concerns about urologic disease. However, the similarity in non-urologic diagnoses and general medical examinations provide some preliminary reassurance that the 55% response rate did not necessarily compromise generalizability.