Background: The objective of this study was to examine whether demographic and lifestyle characteristics are associated with prostate-specific antigen (PSA) levels and the rate of PSA increase (PSA velocity).
Methods: Data for this study came from 3341 participants in the placebo arm of the Prostate Cancer Prevention Trial who, based on biopsies at the end of the study, were free of prostate carcinoma. Linear regression was used to assess associations of age, race, smoking, body mass index (BMI), physical activity, diet, and supplement use with PSA concentration during the second year of the trial, and linear mixed models were used to assess associations of these factors with PSA velocity (the percentage increase in PSA per year) during 6 years of the trial.
Results: Between the group of men ages 50-59 years and the group of men age 70 years and older, mean PSA increased by 0.22 ng/mL, and PSA velocity decreased by 1.2 percentage points (both P < 0.001). The PSA level among men who had a BMI > or = 35 kg/cm(2) was 0.20 ng/mL lower than the PSA level among men who had a BMI < 25 kd/cm(2) (P < 0.001), but BMI was not associated with PSA velocity. PSA velocity was 1.2 percentage points higher in African-American men compared with white men (P = 0.043). Low energy intake and the use of high-dose calcium supplements were associated with significantly lower PSA velocity (both P = 0.05). Weight gain also was associated with lower PSA velocity.
Conclusions: Differences in PSA concentration associated with demographic and lifestyle characteristics were small and were not likely to bias the interpretation of a single PSA test. Age, race, energy intake, calcium supplement use, and weight change were associated with substantial differences in PSA velocity, and the clinical interpretation of PSA velocity may be biased by these factors.