TUESDAY, July 13, 2004 (HealthDayNews) -- The role of social stress in increasing the risk for cancer has not been clearly established, but a new study in monkeys suggests that it could double the possibility for endometrial cancer.
In addition, the study found that moderate drinking doesn't increase the risk of breast or endometrial cancer in postmenopausal women who aren't on hormone replacement therapy (HRT).
"Low social status is associated with markers of increased risk for endometrial cancer in postmenopausal primates," said lead researcher Carol Shively, a professor of comparative medicine at Wake Forest University Baptist Medical Center.
Shively's group studied postmenopausal female monkeys. The researchers placed the monkeys into groups, allowing them to naturally establish a social hierarchy from dominant to subordinate monkeys.
Earlier research has found that subordinate monkeys have increased heart rates, more stress hormones, and increased cardiovascular disease.
The research team measured cell proliferation and sex steroid receptors in the lining of the uterus. They also measured breast tissue thickness, according to their report in the July issue of the journal Menopause.
Compared to dominant monkeys, the socially stressed subordinate monkeys had an increased risk for endometrial cancer.
"It was a twofold increase," Shively said. "This is not a little effect, it is a big effect."
"Low social status is stressful," Shively said. "It is stressful in human beings and in monkeys. It appears that this stress carries with it health consequences."
Shively noted that the effect of stress is difficult to study in humans because people who have a low socioeconomic status are under-represented in the health-care system, making it almost impossible to see the direct effects of stress on health among this group.
Also, Shively said, race plays a role, making it difficult to determine if the differences in disease risk are racial or social.
"The reproductive system of these monkeys is similar to the human reproduction system, which makes them a good model for studying reproductive disorders and diseases," Shively explained.
Shively doesn't know if there are more cases of endometrial cancer among women of low socioeconomic status. But based on the results in monkeys, she believes it's possible.
The subordinate monkeys also had thickening of breast tissue, suggesting that stress might also be a risk for breast cancer, Shively said. "But this finding was not as compelling as the one for endometrial cancer," she added.
"The outcome of this study is a precautionary tale," Kathleen Grant, a professor of physiology and pharmacology at Wake Forest University Baptist Medical Center, said in a statement.
"Social stress, perhaps caused by increases in social isolation and hostile social experiences, or lack of control over social interactions, may place postmenopausal women at risk for breast and endometrial cancer," added Grant, who co-authored an accompanying editorial in the same journal.
The researchers also found that moderate drinking did not increase the risk of breast or endometrial cancer, Shively said.
The monkeys in the trial were given a set amount of alcohol each day. People, Shively noted, often don't accurately report the amount of alcohol they drink; using monkeys eliminated that problem.
"Postmenopausal women who are not on HRT can drink moderately without affecting their breast or endometrial cancer risk," Shively said.
The American Cancer Society can tell you about endometrial cancer.