– The impact of body mass index (BMI) on PSA levels is small according to a report by Dr. Stacy Loeb and colleagues from Johns Hopkins University and the National Institute on Aging that appears in the December, 2009 online edition of the Journal of Urology.
The problem is defined by the fact that in 2001-2002, 65.7% of Americans were overweight or obese, as defined by a BMI of 25.0 to 29.9 and 30kg/m2 or greater, respectively. In addition, several studies have noted a correlation between increased BMI and more aggressive pathological features and worse outcomes. One issue is that overweight and obese men have a larger circulating plasma volume and secondary to hemodilution may have an artificially lower serum PSA. Another possibility is that obesity affects PSA by these men having lower testosterone levels. This study evaluated the association between BMI and PSA in men with and without prostate cancer using the Baltimore Longitudinal Study of Aging (BLSA) database.
The BLSA database began in 1958 and had prospective PSA data collected since 1991 and retrospective PSA measurements performed on frozen sera prior to that. Prostate volumes were measured by pelvic MRI after 1993. Testosterone was available in 713 men and serum plasma volume was calculated.
In “healthy” controls, BMI was not significantly correlated with PSA after adjusting for age in an individual with time. A 10-point increase in BMI would be associated with a 0.03ng/ml PSA decrease. The investigators generated a model to include 179 men diagnosed with prostate cancer and the result was similar. There was a significant inverse relationship between PSA and plasma volume in controls, but no significant relationship between age-adjusted PSA and hematocrit. Using percent body fat rather than BMI as the measure of adiposity was significant, but only modestly so. For each 1% increase in body fat ,the associated increase in change in PSA was -0.0046ng/ml. Prostate volume did not impact the model, but in men with testosterone measurements the relationship between PSA and BMI was significant (coefficient -0.011). Weight gain or loss did not influence the correlation with PSA in men younger or older than 60 years.
Loeb S, Carter HB, Schaeffer EM, Ferrucci L, Kettermann A, Metter EJ
J Urol. 2009 Dec;182(6):2646-51
doi:10.1016/j.juro.2009.08.041
Contributing Editor Christopher P. Evans, MD, FACS
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