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

Background. In epidemiological studies, non-response may raise the que stion of generalizability to the target population. Most investigation s have not been able to access data that could provide information abo ut the potential impact of nonresponse bias. Methods. A 55% response r ate 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 Sym ptoms and Health Status Among Men). This prompted a preliminary study of potential non-response bias among full participants, partial partic ipants and complete non-responders. The medical diagnostic index maint ained by the Rochester Epidemiology Project was used to ascertain the prevalence of specific conditions in the 9 years prior to study incept ion. Results. The age-adjusted period prevalence rate for benign prost atic 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 participan ts and 5.3 (95% CI : 3.6-6.9) for complete non-responders. Other urolo gic diagnoses followed the same pattern. However, age-adjusted prevale nce rates for general medical examination history and major non-urolog ic morbidities were decidedly similar across response groups. Conclusi ons. These data suggest response may have been driven, in part, by con cerns about urologic disease. However, the similarity in non-urologic diagnoses and general medical examinations provide some preliminary re assurance that the 55% response rate did not necessarily compromise ge neralizability.