Purpose
Obesity may be associated with lower prostate-specific antigen (PSA) through hemodilution. We examined the relationship between body mass index (BMI) and PSA by age in men without prostate cancer from a longitudinal aging study to determine whether PSA needs to be adjusted for BMI.
Materials and Methods
The study population included 994 men (4937 observations) without prostate cancer in the Baltimore Longitudinal Study of Aging. Mixed effects models were used to examine the relationship between PSA and BMI (kg/m2) by age. Separate models were explored in men with prostate cancer censored at diagnosis, for percent body fat measurements, for weight changes with time, and adjusting for initial prostate size in 483 men (2523 observations) with pelvic MRI measurements.
Results
In men without prostate cancer, BMI was not significantly associated with PSA after adjusting for age (p=0.06). A 10 point BMI increase was associated with a PSA difference of −0.03 ng/ml (95% CI, −0.40–0.49). Results were similar when men with prostate cancer were included, when percent body fat was substituted for BMI, and after adjusting for prostate volume. Longitudinal weight changes also had no significant association with PSA.
Conclusions
Consistent with prior studies, we found an inverse relationship between obesity and serum PSA levels. However, the magnitude of the difference was small. Thus, adjusting PSA for BMI does not appear warranted.