NEW YORK (Reuters Health) - Cigarette smoking appears to be associated with a decreased risk of cancer of the endometrium, the inner lining of the uterus, research from China suggests.
"The benefit of smoking was observed almost exclusively in postmenopausal women and not in premenopausal women," principal investigator Dr. Bin Wang of Nanjing Medical University told Reuters Health.
However, in spite of this link, "cigarette smoking could dramatically increase the incidence of many other chronic diseases," Wang pointed out.
Endometrial cancer is commonly thought to be linked with exposure to estrogen. It has also been suggested that cigarette smoking exerts an anti-estrogen effect. But previous studies have provided inconsistent findings regarding the link between cigarette smoking and endometrial cancer risk.
Wang and colleagues therefore investigated these relationships by combining data from 34 studies published through June 2007.
Their findings, which appear in The American Journal of Medicine, suggest a history of cigarette smoking decreases the risk of endometrial cancer by 18 to 29 percent. This association was significant for both current and former smokers.
Upon further analysis, the researchers found that a statistically significant relationship was found between smoking and a decreased endometrial cancer risk among postmenopausal women but not premenopausal women. The risk of endometrial cancer among postmenopausal women who smoked was reduced by 29 percent.
Moreover, among women taking hormone replacement therapy, cigarette smoking was associated with about a 50 percent decreased risk of endometrial cancer. But, again, the decreased risk was only significant among postmenopausal women.
There are likely multiple biological mechanisms associated with the link between reduced risk of endometrial cancer among cigarette smokers, Wang and colleagues note.
Other factors, such as alcohol, fruit, and vegetable intake, or physical activity, may have influenced the risk estimates, the researchers surmise, but the studies they reviewed rarely considered these variables.
Further research should assess biologic mechanisms underlying this phenomenon, Wang said. The resulting knowledge might aid the development of strategies for preventing endometrial cancer, he and colleagues note.
SOURCE: The American Journal of Medicine, June 2008.
