Carol Shively, Ph.D., professor of comparative medicine at Wake Forest Baptist and co-author of the study claims, "The results from this study tell us that we need to look much more closely at the effects of stress and socioeconomic status on risk for endometrial and breast cancer in women.
Shively and her colleagues studied the effects of stress and moderate alcohol consumption on breast and endometrial tissue (which lines the uterus). They evaluated type and quantity of cells, density of tissue, number of dividing cells, and number of progesterone and estrogen receptors. The levels of certain sex steroids, like estrogen, and adrenal steroids, like cortisol, were also measured. All of these are considered possible markers for cancer risk.
During the study, postmenopausal female monkeys were arranged in groups so they would naturally establish a social hierarchy of dominance among their peers. Previous research has shown that subordinates have increased heart rates, more of the stress hormone cortisol and more advanced stages of cardiovascular disease. The current study showed that compared to dominant monkeys, the socially stressed subordinate monkeys had an increased risk for endometrial cancer. The disease affects 1 to 2 percent of women and most often occurs in older women.
Shively claims, “We know that lower social status is stressful for both humans and monkeys. This study shows that in monkeys, social stress was associated with cellular changes that may increase endometrial cancer risk.” There were also changes in the monkeys’ breast tissues. Shively also notes, “There may be an effect, but it’s not as strong as in the uterus.”
The researchers also examined the effects of moderate alcohol consumption for risk of breast and endometrial cancer. In humans, several large studies have documented that alcohol consumption, even in moderate doses, appears to positively affect the risk of breast cancer. However, it’s important to note that the studies relied on women’s self-reports of how much they drank. Research shows that most people don’t accurately report their alcohol consumption.
The study was designed to directly compare postmenopausal monkeys who drank a moderate and controlled amount of alcohol with those who didn’t drink alcohol. Half of the monkeys were trained to voluntarily consume two drinks of alcohol every weekday for 26 months.
Shively believes, “The research suggests that moderate alcohol consumption in postmenopausal women not taking hormone therapy may not be harmful to health.”