肥胖是很多腫瘤的危險(xiǎn)因素，但肺癌似乎并不包括內(nèi),。較多的流行病學(xué)研究發(fā)現(xiàn)，體重指數(shù)（BMI）（肥胖的標(biāo)記物）和肺癌的發(fā)生風(fēng)險(xiǎn)成負(fù)相關(guān),。但這些研究都或多或少受到潛在的混雜因素影響,，如吸煙等。于是來自美國國家癌癥研究所Smith等人進(jìn)行了研究,。研究結(jié)果3月16日在線發(fā)表于JNCI,。
這是一項(xiàng)前瞻性的研究，于在1995–1996年納入了年齡在50-71歲間的448732名男性和女性,。BMI根據(jù)研究對象基線時(shí)的身高和體重計(jì)訪截止到2006年,，平均算。隨隨訪時(shí)間9.7年,，共發(fā)生9437例肺癌患者（其中不吸煙者415例）,。多元Cox比例風(fēng)險(xiǎn)回歸模型來計(jì)算患肺癌危險(xiǎn)比（HR）和95%可信區(qū)間（CI）（校正了肺癌的危險(xiǎn)因素，如吸煙狀況）,?？紤]到既往病史可能帶來的偏倚，研究者在敏感性分析時(shí)剔除了潛在的非健康研究對象,。所有的統(tǒng)計(jì)檢驗(yàn)均為雙側(cè),。
研究發(fā)現(xiàn)肺癌的發(fā)病率為男性233例/100000人年，女性為192例/100000人年,。無論是男性還是女性,，BMI均與肺癌發(fā)生風(fēng)險(xiǎn)呈負(fù)相關(guān)（BMI≥35 VS 22.5-24.99 kg/m2：HR= 0.81，95%CI= 0.70-0.94和HR= 0.73,，95%CI =0.61-0.87）,。這種負(fù)相關(guān)僅存在于吸煙（包括既往有吸煙史）人群，且在校正吸煙因素后,，這種負(fù)相關(guān)變強(qiáng),。在吸煙人群中進(jìn)一步亞組分析，分組因素包括戒煙的時(shí)間,，每天吸煙的支數(shù)等，在各亞組中BMI均與肺癌發(fā)生風(fēng)險(xiǎn)負(fù)相關(guān),。敏感性分析的結(jié)果支持這種負(fù)相關(guān)與既往病史無關(guān),。由此可得出結(jié)論：在吸煙者中，較高的BMI可以降低肺癌的發(fā)生風(fēng)險(xiǎn),。（生物谷 bioon.com）
doi:10.1093/jnci/djs179
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Body Mass Index and Risk of Lung Cancer Among Never, Former, and Current Smokers
Llewellyn Smith, Louise A. Brinton, Margaret R. Spitz, Tram Kim Lam, Yikyung Park, Albert R. Hollenbeck, Neal D. Freedman and Gretchen L. Gierach
Background Although obesity has been directly linked to the development of many cancers, many epidemiological studies have found that body mass index (BMI)—a surrogate marker of obesity—is inversely associated with the risk of lung cancer. These studies are difficult to interpret because of potential confounding by cigarette smoking, a major risk factor for lung cancer that is associated with lower BMI. Methods We prospectively examined the association between BMI and the risk of lung cancer among 448?732 men and women aged 50–71 years who were recruited during 1995–1996 for the National Institutes of Health–AARP Diet and Health Study. BMI was calculated based on the participant’s self-reported height and weight on the baseline questionnaire. We identified 9437 incident lung carcinomas (including 415 in never smokers) during a mean follow-up of 9.7 years through 2006. Multivariable Cox proportional hazards regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) with adjustment for lung cancer risk factors, including smoking status. To address potential bias due to preexisting undiagnosed disease, we excluded potentially unhealthy participants in sensitivity analyses. All statistical tests were two-sided. Results The crude incidence rate of lung cancer over the study follow-up period was 233 per 100?000 person-years among men and 192 per 100?000 person-years among women. BMI was inversely associated with the risk of lung cancer among both men and women (BMI ≥35 vs 22.5–24.99 kg/m2: HR = 0.81, 95% CI = 0.70 to 0.94 and HR = 0.73, 95% CI = 0.61 to 0.87, respectively). The inverse association was restricted to current and former smokers and was stronger after adjustment for smoking. Among smokers, the inverse association persisted even after finely stratifying on smoking status, time since quitting smoking, and number of cigarettes smoked per day. Sensitivity analyses did not support the possibility that the inverse association was due to prevalent undiagnosed disease. Conclusions Our results suggest that a higher BMI is associated with a reduced risk of lung cancer in current and former smokers. Our inability to attribute the inverse association between BMI and the risk of lung cancer to residual confounding by smoking or to bias suggests the need for considering other explanations.
