女性超重和肥胖时间越久，乳腺癌等癌症风险越大

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　　2016年8月16日，美国《公共科学图书馆·医学》在线发表法国里昂国际癌症研究机构（IARC）、美国加利福尼亚大学欧文分校、斯坦福大学、田纳西大学、纽约石溪大学、凯撒医疗波特兰健康研究中心、弗雷德·哈钦森癌症研究中心、阿尔伯特·爱因斯坦医学院、维克弗斯特医学院、以色列海法大学的研究报告，发现女性群体超重（体重指数≥25kg/m²）和肥胖（体重指数≥30kg/m²）的时间越长，患乳腺癌等癌症的风险就越高。

　　该研究基于政府资助的女性健康倡议计划，主要致力于对美国50～79岁女性的健康研究，首先测量女性当前体重和身高，并要求她们回忆自己在18、35、50岁时的体重。

　　结果，73913位美国女性经过平均12.6年随访，有6301位女性患上与肥胖相关的癌症，如乳腺癌、卵巢癌、子宫内膜癌、结肠癌、肾癌、肝癌或胰腺癌。这些类型的癌症的患病风险与女性曾经的超重和肥胖时间呈正相关。

　　平均而言，女性超重和肥胖状态每保持10年，所有肥胖相关癌症发生率增加7%，绝经后乳腺癌和子宫内膜癌的风险分别增加5%、17%。校正超重程度后，绝经后乳腺癌和子宫内膜癌的风险分别增加8%、37%。

PLoS Med. 2016 Aug 16;13(8):e1002081.

Duration of Adulthood Overweight, Obesity, and Cancer Risk in the Women's Health Initiative: A Longitudinal Study from the United States.

Arnold M, Jiang L, Stefanick ML, Johnson KC, Lane DS, LeBlanc ES, Prentice R, Rohan TE, Snively BM, Vitolins M, Zaslavsky O, Soerjomataram I, Anton-Culver H.

International Agency for Research on Cancer, Lyon, France; University of California, Irvine, California, USA; Stanford University, Stanford, California, USA; University of Tennessee Health Science Center, Memphis, Tennessee, USA; Stony Brook University School of Medicine, Stony Brook, New York, USA; Center for Health Research, Kaiser Permanente, Portland, Oregon, USA; Fred Hutchinson Cancer Research Center, Seattle, Washington, USA; Albert Einstein College of Medicine, Bronx, New York, USA; Wake Forest School of Medicine, Winston-Salem, North Carolina, USA; University of Haifa, Haifa, Israel.

BACKGROUND: High body mass index (BMI) has become the leading risk factor of disease burden in high-income countries. While recent studies have suggested that the risk of cancer related to obesity is mediated by time, insights into the dose-response relationship and the cumulative impact of overweight and obesity during the life course on cancer risk remain scarce. To our knowledge, this study is the first to assess the impact of adulthood overweight and obesity duration on the risk of cancer in a large cohort of postmenopausal women.

METHODS AND FINDINGS: Participants from the observational study of the Women's Health Initiative (WHI) with BMI information from at least three occasions during follow-up, free of cancer at baseline, and with complete covariate information were included (n = 73,913). Trajectories of BMI across ages were estimated using a quadratic growth model; overweight duration (BMI ≥ 25 kg/m2), obesity duration (BMI ≥ 30 kg/m2), and weighted cumulative overweight and obese years, which take into account the degree of overweight and obesity over time (a measure similar to pack-years of cigarette smoking), were calculated using predicted BMIs. Cox proportional hazard models were applied to determine the cancer risk associated with overweight and obesity duration. In secondary analyses, the influence of important effect modifiers and confounders, such as smoking status, postmenopausal hormone use, and ethnicity, was assessed. A longer duration of overweight was significantly associated with the incidence of all obesity-related cancers (hazard ratio [HR] per 10-y increment: 1.07, 95% CI 1.06-1.09). For postmenopausal breast and endometrial cancer, every 10-y increase in adulthood overweight duration was associated with a 5% and 17% increase in risk, respectively. On adjusting for intensity of overweight, these figures rose to 8% and 37%, respectively. Risks of postmenopausal breast and endometrial cancer related to overweight duration were much more pronounced in women who never used postmenopausal hormones. This study has limitations because some of the anthropometric information was obtained from retrospective self-reports. Furthermore, data from longitudinal studies with long-term follow-up and repeated anthropometric measures are typically subject to missing data at various time points, which was also the case in this study. Yet, this limitation was partially overcome by using growth curve models, which enabled us to impute data at missing time points for each participant.

CONCLUSIONS: In summary, this study showed that a longer duration of overweight and obesity is associated with an increased risk of developing several forms of cancer. Furthermore, the degree of overweight experienced during adulthood seemed to play an important role in the risk of developing cancer, especially for endometrial cancer. Although the observational nature of our study precludes inferring causality or making clinical recommendations, our findings suggest that reducing overweight duration in adulthood could reduce cancer risk and that obesity prevention is important from early onset. If this is true, health care teams should recognize the potential of obesity management in cancer prevention and that excess body weight in women is important to manage regardless of the age of the patient.

PMID: 27529652

DOI: 10.1371/journal.pmed.1002081