The natural history of prostatism: the effects of non-response 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 non-response 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.