Clinical research study
Cigarette Smoking and the Risk of Endometrial Cancer: A Meta-Analysis

https://doi.org/10.1016/j.amjmed.2008.01.044Get rights and content

Abstract

Objective

Epidemiologic findings are inconsistent concerning the association of endometrial cancer risk with cigarette smoking. We conducted a meta-analysis of epidemiologic studies to examine this relation.

Methods

A systematic literature search up to June of 2007 was performed in MEDLINE and EMBASE. Study-specific risk estimates were pooled using a random-effects model.

Results

Ten prospective and 24 case-control studies were included in the analysis of the effect of ever smoking. Ever smoking was statistically significantly associated with a reduced risk of endometrial cancer among prospective studies (relative risk 0.81; 95% confidence interval [CI], 0.74-0.88) and case-control studies (odds ratio 0.72; 95% CI, 0.66-0.79). The inverse association was significant among current and former smokers. Six prospective and 6 case-control studies were included in the quantitative analysis. We noted that an increase in smoking of 20 cigarettes per day was statistically significantly associated with 16% and 27% reduced risks of endometrial cancer in prospective and case-control studies, respectively. We also found that cigarette smoking was significantly associated with a decreased risk of endometrial cancer among postmenopausal women (relative risk 0.71; 95% CI, 0.65-0.78) but not among premenopausal women. In addition, the risk reduction seemed to be stronger among hormone replacement therapy users than nonusers.

Conclusion

Cigarette smoking was found to be significantly associated with a reduced risk of endometrial cancer, especially among postmenopausal women.

Section snippets

Search Strategy

A systematic literature search up to June of 2007 was performed in MEDLINE and EMBASE to identify relevant studies. Search terms included “smoking,” “tobacco,” or “lifestyle,” combined with “endometrial cancer,” “uterine corpus cancer,” or “endometrial carcinoma.” The search was limited to English-language articles. The titles and abstracts were scanned to exclude any clearly irrelevant studies. The full texts of the remaining articles were read to determine whether they contained information

Results

We identified 10 prospective21, 22, 23, 24, 25, 26, 27, 28, 29, 30 and 24 case-control studies31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54 of association between cigarette smoking and risk of endometrial cancer (Table 1, available online). Five of 10 prospective studies were conducted in Europe,21, 22, 23, 24, 28 4 studies were conducted in the United States,26, 27, 29, 30 and 1 study was conducted in Canada.25 Of the 24 case-control studies

Discussion

Our meta-analysis has assessed the relation between cigarette smoking and endometrial cancer risk. Overall, smoking was statistically significantly associated with 18% and 29% reduced risks of endometrial cancer in prospective and case-control studies, respectively.

Although cigarette smoking could dramatically increase the incidence of many other chronic diseases, the findings of this meta-analysis have direct public health importance. The elucidation of underlying mechanisms whereby smoking

Conclusions

Our meta-analysis of all prospective and case-control studies demonstrates that cigarette smoking is associated with a lower risk of endometrial cancer, especially among postmenopausal women.

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    *Drs Zhou, Yang, and Sun contributed equally to this work.

    This work was supported by grants from the National Natural Science Foundation of China (No 30672486), the Natural Science Foundation of Jiangsu Province (No BK2006525), 333 Project, Qinglan Project, and Six Rencai Gaofeng Project (No 07C008) for the Young Academic Leader of Jiangsu Province to Dr. Wang.

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