Natural history of prostatism: relationship among symptoms, prostate volume and peak urinary flow rate.

We describe relationships among symptoms, prostate volume and peak urinary flow rate in an age stratified, community based random sample of white men 40 to 79 years old with no prior prostate surgery, prostate cancer or other conditions known to interfere with voiding. Symptoms were assessed with an instrument comparable to the American Urological Association symptom index. Prostate volume was estimated by transrectal ultrasonography and peak urinary flow rate was measured by a portable device. Subject age was significantly associated with symptom score but accounted for only 3% of its variation, while prostate volume and peak urinary flow rate explained only an additional 10% of the symptom variability. The odds (95% confidence interval) of moderate to severe symptoms increased with age from 1.9 (1.1 to 3.1), 2.9 (1.7 to 5.0) and 3.4 (1.8 to 6.1) for men 50 to 59, 60 to 69 and 70 to 79 years old, respectively, relative to men 40 to 49 years old. Adjusting for age, the odds of moderate to severe symptoms were 3.5 times greater for men with prostatic enlargement (more than 50 ml.) than for men with smaller prostates, while the odds were similarly increased (2.4-fold) for men not achieving a peak urinary flow rate of 10 ml. per second. Estimated odds changed little when other cutoff points were considered for peak urinary flow rate (15 ml. per second) or prostate volume (40 ml.). These results, based on randomly selected white men, suggest a somewhat stronger, albeit modest, relationship among symptoms, prostate size and urinary flow rate than previously reported in clinic based studies. The strength of these relationships is comparable to that found with other diseases.