Japanese men have smaller prostate volumes but comparable urinary flow rates relative to American men: results of community based studies in 2 countries.

PURPOSE: We compared prostate volume and peak urinary flow rate in Japanese and American men 40 to 79 years old.
MATERIALS AND METHODS: Prostate volume and peak urinary flow rate were measured in eligible Japanese men and results were compared to those of a randomly selected American cohort.
RESULTS: Mean prostate volume plus or minus standard deviation averaged 20.3 +/- 10.6 ml. in Japanese and 29.6 +/- 13.4 ml. in American men, while predicted cross-sectional increases with age decade were 1.5 and 5.5 ml., respectively. Peak urinary flow rate was higher but the decrease with increasing age was greater in Japanese men.
CONCLUSIONS: Prostate volume is larger and the increase with age is more pronounced in American than in Japanese men. However, Japanese men may have a higher peak urinary flow rate and greater cross-sectional decrease with age.