Obesity-related metabolic diseases may influence prostatic hyperplasia. This study examined the impact of obesity on prostate volume in men without overt obesity-related metabolic diseases. We recruited 146 men over the age of 40 years who did not have overt obesity-related diseases, such as diabetes, impaired fasting glucose, hypertension, or dyslipidemia. Transrectal ultrasonography was performed on all subjects. The subjects were divided into three groups according to their BMI: normal (18.5 to 22.9 kg/m2), overweight (23 to 24.9 kg/m2), and obese (> or = 25 kg/m2), and two groups according to their waist circumference: normal waist (< or = 90 cm) and central obesity (> 90 cm). The classification of the subgroups was based on the Asia-Pacific criteria of obesity. We compared the prostate volume among subgroups and assessed factors related to prostatic hyperplasia. Mean prostate volume was 18.8 +/- 5.0, 21.8 +/- 7.2, and 21.8 +/- 5.6 mL in the normal, overweight, and obese groups, respectively, and was 20.0 +/- 5.9 and 23.7 +/- 5.3 mL in the normal waist and central obesity group, respectively. Prostate volume was significantly greater in the obese group than in the normal group (P = 0.03) and in the central obesity group compared with the normal waist group (P = 0.002). Prostate volume was positively correlated with BMI and waist circumference after adjustment for age. After adjusting for confounding factors, central obesity was an independent factor affecting prostatic hyperplasia, which was defined as a prostate volume > 20 mL (odds ratio = 3.37, p = 0.037). Relative to men with both low BMI (18.5 to 22.9 kg/m2) and normal waist circumference, those with high BMI (> or = 25 kg/m2) and central obesity were at significantly increased risk of prostatic hyperplasia (odds ratio = 4.88, p = 0.008). However, those with high BMI (> or = 25 kg/m2) and normal waist circumference were not at significantly increased risk. Prostate volume was greater in the obese and central obesity groups than in the normal group after patients with overt obesity-related metabolic diseases were excluded. Although both BMI and waist circumference were positively correlated with prostate volume, central obesity was the only independent factor affecting prostate hyperplasia. We suggest that central obesity is an important risk factor for prostatic hyperplasia.
