An inverse association of obesity and prostate-specific antigen in elderly males

Objective: Serum prostate-specific antigen (PSA) test is commonly applied for prostate cancer screening and diagnosis. However, the level of PSA varied in different races and can be influenced by many factors. Previous studies show that obese is related to the PSA level, but the results are highly inconsistent. The aim of this study was to examine the relationships among body mass index (BMI), waist circumference (WC) and serum PSA including PSA density (PSAD) and PSA increasing rate (PSAR) in healthy males, and to investigate whether this relationship was independent to other factors. Methods: Cross-sectional analysis was in men aged from 60 to 85 years (N=4,084) without prostate cancer and had health examination between August 2008 and July 2014 in a clinical center in Xi’an, China. Obesity (BMI≥27.5 kg/m2) and overweight (27.5>BMI≥22.5 kg/m2), the control (WC≤90 cm) and the central obesity (WC>90 cm) were classified according to the WHO criterion respectively. Mean (SD) PSA level, PSAD, PSAR was calculated by categories (the control, overweight, and obesity). The association between BMI, WC and PSA, PSAD, PSAR stratified by age was tested by using multivariate regression models. Results: In the enrolled study population, the prevalence was 55.42% for overweight and 10.22% for obese, 82.65% for the control and 17.35% for central obese. BMI, WC was negatively associated with PSA level (P<0.05), independent to fasting blood glucose (FBG) and prostate volume (P<0.05). BMI was significantly associated with lower level of PSA (P=0.032), in independent of FBG (P=0.021). However, the negative correlation was not statistically significant in age (P=0.063) and PV (P=0.085) adjusted models. BMI was not significantly related to lower level of PSAD, PSAR (P=0.123, 0.307, respectively) after adjusted by age. The multivariate regression results of WC and PSA stratified by age showed similar results. Conclusions: Our results indicate that obesity is associated with a lower level of PSA in healthy males in all age groups, but independent to FPG. With the current obesity epidemic, individual’s BMI, WC should be considered, especially BMI. PSA test is applied for prostate cancer screening or diagnose. Despite the inverse association for PSA test would not be available for males older than 60 years, it is suggested that that PSAD or PSAR levels should be selected for estimation.