Effect of body mass index on prostate-specific antigen and percentage free prostate-specific antigen: Results from a prostate cancer screening cohort of 1490 men

Several studies have reported an effect of obesity, defined as elevated body mass index (BMI), on prostate cancer biology. We examined the relationship between BMI and total prostate-specific antigen (tPSA) as well as percent free tPSA (%f/tPSA) in a large prostate cancer screening cohort. Height, weight, tPSA and %f/tPSA were assessed in 1490 consecutively screened Canadian men without known prostate cancer. Continuously coded and categorized BMI were studied. Statistical analyses consisted of anova, linear regression and bivariate correlations, which adjusted for the effect of age. Median tPSA was 1.06 ng/mL and median %f/tPSA was 27. Median BMI was 26.17 kg/m(2). Increasing BMI was weakly, albeit statistically significantly, associated with decreasing %f/tPSA values (correlation coefficient = -0.06, P = 0.01). However, when the World Health Organization BMI categories were considered, there were no statistically significant differences between %f/tPSA values according to categories (anova P = 0.2). tPSA failed to demonstrate any statistically significant association with either continuously coded (correlation coefficient = -0.03, P = 0.2) or categorized BMI (anova P = 0.5). Body mass index is not a confounder of either tPSA or %f/tPSA in Canadian men without known prostate cancer.