The metabolic syndrome is associated with reduced risk of prostate cancer.

Diabetes is associated with reduced risk of prostate cancer, but whether the metabolic syndrome is associated with prostate cancer is not established. The authors assessed this association in the Atherosclerosis Risk in Communities (ARIC) Study, comprising 6,429 men in four US communities initially with no history of cancer and aged 45-64 years. Metabolic syndrome and other risk factors were assessed in 1987-1989. Follow-up for prostate cancer incidence (n = 385 through 2000) was accomplished through cancer registry and hospital linkage. At baseline, 1,871 men (29.5%) had the metabolic syndrome. After the authors adjusted for other risk factors, men with the metabolic syndrome (> or =3 components) were significantly less likely to develop prostate cancer (relative risk = 0.77, 95% confidence interval: 0.60, 0.98) than men without the metabolic syndrome. Diabetes was negatively associated with prostate cancer, although the confidence interval included 1 (relative risk = 0.73, 95% confidence interval: 0.51, 1.05). When diabetic participants were excluded, the inverse association between metabolic syndrome and prostate cancer incidence was slightly strengthened. In this study, the metabolic syndrome was associated with decreased prostate cancer incidence. The authors hypothesize that this finding reflects a decrease in bioavailable (free and albumin-bound) testosterone with the metabolic syndrome and a concomitant reduction in prostate cancer risk.