NEW YORK (Reuters Health) — Men with long-term diabetes may have a reduced risk of prostate cancer, according to the results of a study published in the American Journal of Epidemiology.“Recent studies have suggested an association between type 2 diabetes mellitus and lower risk of prostate cancer,” Dr. Mona Saraiya and colleagues from the Centers for Disease Control and Prevention, Atlanta, write.

“It has been hypothesised that men with long-term diabetes have a lower risk of prostate cancer than non-diabetic men, and recently diagnosed men have a higher risk.”

In the current study, the researchers used data from the National Health and Nutrition Examination Survey 2001 to 2002 to investigate the association between diabetes and prostate-specific antigen (PSA) levels, a biological marker for prostate cancer. Higher PSA levels indicate an increased risk of cancer. The researchers adjusted the findings for the effect of known potential risk factors. For subjects without a diagnosis of diabetes, the researchers used fasting blood sugar measurements to determine the presence of undiagnosed diabetes.

The average PSA levels were 21.6 percent lower among men with a self-reported diagnosis of diabetes compared with men without diabetes.

This difference increased with years since the diabetes diagnosis was made. Men diagnosed more than ten years ago had a 27.5 percent lower average PSA level.

Overweight men who had been diagnosed with diabetes more than ten years ago had a PSA level that was 40.8 percent lower than normal-weight men without diabetes.

“It is unclear whether the lowered PSA level in diabetic men accurately reflects a decreased risk of prostate cancer in the diabetic population or whether their lower PSA levels result in a reduced likelihood of receiving a diagnostic work-up for detection of asymptomatic prostate cancers, as has been suggested for obese men,” Saraiya and colleagues note.

“If the latter were true, diabetic men might well be diagnosed with later-stage tumours and have poorer treatment outcomes, and overweight diabetic men would have later-stage tumours than normal-weight diabetic men.”