Behavioral risk factors have a significant effect on cancer risk in the U.S. elderly population, according to research presented at the American Association for Cancer Research's Seventh Annual International Conference on Frontiers in Cancer Prevention Research. Understanding these factors may allow clinicians to make specific recommendations for their elderly patients in order to reduce their risks of future cancers.
"About 80 percent of all cancers are diagnosed in the elderly, and more than 80 percent of known risk factors are potentially preventable," said Igor Akushevich, Ph.D., senior research scientist, Center for Population Health and Aging, Duke University, Durham, N.C.
The primary purpose of the Duke study was to develop an approach to estimate the contributions of measurable risk factors to cancer risk among the elderly. More analysis is needed before the findings can be applied in clinical use.
"So far, we have not come to the stage where we are able to make specific recommendations regarding risk factors," Akushevich said. "However, we can confirm several of them which are known. As expected, we see associations of cigarette smoking with lung cancer. Moderate physical activities are capable of decreasing cancer risk, as well as careful health care insurance strategy and, hypothetically, general optimism in life."
Although the results need to be verified in subsequent studies, the researchers found significant contributions from a variety of lifestyle, behavioral and demographic variables on the risk of breast, lung, colon and prostate cancers among the elderly.
The study used data from The National Long Term Care Survey (NLTCS), Medicare claims and the Surveillance, Epidemiology and End Results Program. It defined elderly as 65 years of age or greater. "What is important," Akushevich said, "is the sample of individuals represents the whole U.S. elderly population."
Some associations between risk factors and cancer incidence were significant and were similar to those found in previous NLTCS studies. "Light physical activities decrease risk of cancer, and moderate activities decrease the risks in larger extent, while the picture for vigorous activities is contradictory," he said. Colon and prostate cancers were more associative with physical activities. The preventive effect of physical activities, however, may be mitigated by an increasing risk of death due to all causes as people age.
As expected, tobacco consumption was significantly associated with lung cancer. Future research will examine any joint effects of cigarette smoking and other risk factors such as physical activity or obesity, Akushevich said.
The effect of comorbidities demonstrated a larger increase in risk seen for breast and prostate cancers and a lesser increase for lung and colon cancers. Circulatory disease and diabetes increased the risk of breast cancer while immune diseases increased the risk of prostate cancer.
All data came from individuals covered by Medicare. The researchers found an increased cancer and mortality risk depending on the specific Medicare plan. "The situation when additional payments have to be made out-of-pocket is the worst in respect to cancer and mortality risk," Akushevich said. "The problem is more important for lung and colon cancers."
He added the researchers were surprised at some of the findings. Cancer risk was not associated with alcohol consumption, which has been reported in other studies. A possible explanation may be a moderate level of alcohol consumption by the elderly.
"Other interesting associations are increased risk of breast cancer for those women afraid to go to the doctor to investigate health problems and a decreased risk of breast and lung cancers for those who never lose their temper," he said.
"A general view of the results leads to a hypothesis that cancer risk increases for individuals who are not completely happy in different aspects of their life," he added.
Future research will entail detailed multivariate analyses and comparison of predictions with other data sets. "We hope to find confirmation of found associations and to more extensively study effects of risk factors," Akushevich said.
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