Observed effect of age and body mass index on total and complexed PSA: analysis from a national screening program.

OBJECTIVES

To assess the effect of aging and body mass index (BMI) on both serum total prostate-specific antigen (tPSA) and complexed PSA (cPSA) from the results of the 2003 Prostate Cancer Awareness Week national screening database.

METHODS

A total of 12,943 men were screened for prostate cancer. Of these, 4458 men had simultaneous measurements of tPSA and cPSA. Height and weight were used to calculate the BMI. The subjects were grouped by decade of age and categorized as either obese or nonobese with a cutoff BMI of 30 kg/m2. The rates of increase in mean tPSA and cPSA between consecutive decades were compared. The relationship among BMI, PSA, and cPSA was also analyzed using multivariate regression analysis.

RESULTS

The median age of those screened was 60 years. The median PSA and cPSA was 1.10 and 0.69 ng/dL, respectively. Both serum tPSA and cPSA levels showed an exponential increase with advancing age. The ratio of cPSA/tPSA remained relatively constant at 0.6. Compared with the nonobese cohort, men with a BMI of 30 kg/m2 or more had significantly lower tPSA and cPSA levels across all age groups (P <0.01). The overall odds ratio for all age groups was 1.8 (95% confidence interval 1.2 to 2.3).

CONCLUSIONS

Both tPSA and cPSA levels increased with age. Across age groups, men with a greater BMI had significantly lower cPSA and tPSA levels. The clinical significance of age-adjusted cutoff levels for PSA in obese men for the diagnosis of prostate cancer should be explored further in future prospective clinical trials.