Obesity before age 30 years and risk of advanced prostate cancer.

Adult obesity has shown little association with prostate cancer risk, but obesity at younger ages may be associated with reduced risk. In 1997-2000, the relation between obesity before age 30 years and incident advanced prostate cancer was investigated in a population-based case-control study of African-American and White men (568 cases, 544 controls) in California. Unconditional logistic regression was used to estimate odds ratios and 95% confidence intervals, adjusted for age, race, family history of prostate cancer, and saturated fat intake. Measures of obesity for age 10 years tended to be inversely associated with prostate cancer (odds ratio (OR) = 0.79, 95% confidence interval (CI): 0.46, 1.38 for selecting the "obese" pictogram and OR = 0.76, 95% CI: 0.52, 1.11 for reporting being heavier than peers). The decreased risk was more pronounced at ages 20-29 years (OR = 0.53, 95% CI: 0.28, 1.00 for the "obese" drawing, OR = 0.59, 95% CI: 0.40, 0.88 for being heavier than peers, and OR = 0.40, 95% CI: 0.20, 0.81 for body mass index > or =30 kg/m(2)). In addition, both "obese" and small waist size at ages 20-29 years showed inverse trends. This research implicating early-life body size in prostate cancer development helps to elucidate causal mechanisms, such as altered sex hormone profiles during critical developmental periods, potentially involved in development of the disease.