Effects of obesity and height on prostate-specific antigen (PSA) and percentage of free PSA levels among African-American and Caucasian men

BACKGROUND. Prior studies suggest that obese men have lower prostate-specific antigen (PSA) levels than leaner men. Caucasian (CA) men also may have lower PSA levels than African-American (AA) men, but the relevance of body size to racial disparities in PSA levels is unclear. The association between body mass index (BMI) and height on PSA and percentage of free PSA (%fPSA) was investigated within AA and CA men without a prior prostate cancer diagnosis. METHODS. AA (n = 150) and CA (n = 149) men of similar socioeconomic status completed an extensive in-person interview and donated blood. PSA and %fPSA levels were compared across race, BMI, and height categories after adjusting for age and other factors. RESULTS. PSA levels decreased with increasing BMI (PSA = .72, .69, .67, .59 ng/mL for BMI 18.5 to < 25, 25 to < 30, 30 to < 35, and >= 35, respectively; P-trend = .18), and trends were significant among men less than age 60 years (PSA = .81, .76, .66,.59, respectively; P-trend = .02). fPSA also significantly decreased with BMI among men < 60 years (P-trend = .04). In contrast, %fPSA was not associated with BMI. However, %fPSA increased 27% across height categories (P-trend = .02). PSA levels were significantly lower among CA men (PSA(AA) = 0.87, PSA(CA) = 0.63 ng/mL; P < .01), whereas %fPSA levels did not differ by race. Also, associations between body size and PSA or %fPSA did not significantly differ by race, and adjustment for BMI and height had no effect on the racial disparity in PSA (PSA(AA) = 0.87, PSA(CA) = 0.63 ng/mL; P < .01). CONCLUSION. The data suggest that race, BMI, and height are independently associated with PSA and %fPSA levels.