Weight gain in adulthood associated with prostate Ca risk

Body mass in younger and older adulthood, and weight gain between these periods, may influence a man’s risk for prostate cancer, and the risk varies among different ethnic populations, report researchers from the University of Hawaii, Honolulu.

"The relationship of certain characteristics, such as body size, with cancer risk may vary across ethnic groups due to the combined influence of both genes and lifestyle," said first author Brenda Y. Hernandez, PhD, MPH.

The team used the Multiethnic Cohort, a longitudinal study of men aged 45 to 75 years old established in Hawaii and California from 1993 to 1996. Of the 83,879 men who participated in this study, 5,554 were diagnosed with prostate cancer.

Overall, men who were overweight or obese by age 21 had a decreased risk of localized and low-grade prostate cancer, according to Dr. Hernandez. Being overweight in older adulthood was associated with increased risk of prostate cancer among Caucasian and Native Hawaiian men, but a decreased risk among Japanese men. Excessive weight gain between younger and older adulthood increased the risk of advanced and high-grade prostate cancers in Caucasian men and increased the risk of localized and low-grade disease in African-American men, but decreased the risk of localized prostate cancer in Japanese men.

"Readers… might initially look at these results and discount them for being inconsistent across the racial/ethnic groups, but they should not," said Elizabeth A. Platz, ScD, MPH, of the Johns Hopkins Bloomberg School of Public Health, Baltimore, who was not affiliated with the study. "There is no reason to think that the differences in results by ethnicity are explained by bias. Different racial and ethnic populations tend to have differing proportions of fat relative to lean mass and carry their fat mass differently.

"These differences may be used as a launching point for the next line of research: the nature of the weight gain-amount of fat gained and distribution of the fat gained in association with prostate cancer risk overall, and by stage and grade."

Results of the study were published in Cancer Epidemiology, Biomarkers & Prevention (2009; 18:2413-21).