MONDAY, Jan. 8, 2007 (HealthDay News) -- Prostate cancer patients who are overweight or obese are at higher risk of dying from their illness, a new study reveals.
The researchers did not, however, find a connection between being obese and developing the disease in the first place.
"Even though we didn't find that obesity increases the risk of developing prostate cancer, we did find that it does actually increase the risk from dying from it, so this study really sheds more light on the obesity connection," said lead author Margaret E. Wright, a research fellow with the division of Cancer Epidemiology and Genetics at the National Cancer Institute.
Reporting in the Feb. 15 issue of Cancer, Wright and her colleagues pointed out that as recently as 2000, almost two-thirds of American men and women were classified as overweight or obese.
Although prior research hadn't uncovered a clear association between obesity and an elevated risk for the onset of prostate cancer, the authors noted that excess weight is clearly linked to risk increases for type 2 diabetes, cardiovascular disease, chronic illnesses and many other types of cancer.
According to the Prostate Cancer Foundation, prostate cancer strikes one in six American men and is the most prevalent form of non-skin cancer in the United States. Risk rises with age, with more than 65 percent of all cases diagnosed in men over the age of 65.
As for risk factors, both genetics and lifestyle choices -- particularly diet and exercise habits-- are thought to play a role.
Focusing on body mass index -- a ratio of weight to height -- as one potential risk factor for the onset and development of prostate cancer, Wright and her colleagues analyzed health questionnaires completed by nearly 288,000 men who were between the ages of 50 and 71 when the study started in 1995.
All the men were members of AARP and were participating in a larger diet and health study initiated by the organization. In the smaller BMI sample, none of the men had been previously diagnosed with cancer, except for non-melanoma skin cancer.
The initial questionnaire -- as well as a subsequent 1996 follow-up completed by almost 173,000 of the participants -- collected information on height, weight, BMI, and the frequency with which patients underwent prostate-specific antigen (PSA) testing and digital rectal exams (DRE) in the three years prior to the study.
The researchers noted that when the study began, about 29 percent of the men were normal weight, 50 percent were overweight and 21 percent were obese.
Wright and her team found from 1995 to the end of 2000, nearly 10,000 of the men developed prostate cancer. By the end of 2001, 173 of these men had died of the disease.
The study authors found that the risk of death from prostate cancer appeared to increase as BMI increased. Compared to men of normal weight, overweight men had a 25 percent higher risk of dying from the disease. Mildly obese men -- those with a BMI between 30 and 34.9 -- had a 46 percent higher risk. And severely obese men -- those with a BMI of 35 or more -- had double the normal fatality risk.
What's more, the more weight a man gained after age 18, the greater the risk of dying if diagnosed with prostate cancer.
Age, race, family history of prostate cancer, and screening history did not seem to have any impact on the observed link between too much weight and fatality risk.
The authors suggested that theirs was the first study to uncover evidence of the BMI-prostate cancer fatality link.
"This is a large study, and this finding really solidifies prior indications suggesting this association is real," she said. "So while we still need to do more research to find out exactly how this works, I'm not surprised with the connection."
"We have to continue to address the growing prevalence of obesity in this country and others," Wright added, "because obesity is linked to many, many diseases. So we would, of course, definitely recommend that people maintain a healthy weight through diet and exercise."
A person who's 5-feet, 8-inches tall and weighs 160 pounds has a BMI of 24.3. If that same person weighed 180 pounds, the BMI would be 27.4. It would be 31.9 if that person weighed 210 pounds.
Dr. Philip Arlen, director of the Clinical Research Group in the Laboratory of Tumor Immunology and Biology with the Center for Cancer Research at the National Cancer Institute, said he wasn't surprised at the apparent link between obesity and prostate-cancer mortality.
"This adds to observations in a number of different studies that indicate that patients who are in better condition -- thinner, more active, or with a lower BMI -- may have a less aggressive form of cancer and do better than patients who have a sedentary lifestyle," said Arlen. He was not part of the research team.
"There are a lot of factors that may come into play, and BMI may not be predictive in terms of developing prostate cancer," he added. "But it does seem that among patients already diagnosed, those who are physically active and not obese may face a better outcome."
To calculate your BMI, visit the U.S. National Heart, Lung, and Blood Institute.