Sleep Duration Across the Adult Lifecourse and Risk of Lung Cancer Mortality: a Cohort Study in Xuanwei, China Jason Y.Wong1, Bryan A
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Published OnlineFirst April 4, 2017; DOI: 10.1158/1940-6207.CAPR-16-0295 Research Article Cancer Prevention Research Sleep Duration across the Adult Lifecourse and Risk of Lung Cancer Mortality: A Cohort Study in Xuanwei, China Jason Y.Wong1, Bryan A. Bassig1, Roel Vermeulen2, Wei Hu1, Bofu Ning3, Wei Jie Seow1,4,5, Bu-Tian Ji1, George S. Downward2, Hormuzd A. Katki1, Francesco Barone-Adesi6, Nathaniel Rothman1, Robert S. Chapman7, and Qing Lan1 Abstract Sufficient sleep duration is crucial for maintaining normal 2011, adjusted for demographic, anthropometric, medical, and physiological function and has been linked to cancer risk; household characteristics. J-shaped relationships were found however, its contribution to lung cancer mortality is unclear. between average sleep duration and lung cancer mortality. The Therefore, we evaluated the relationship between average sleep patterns were consistent across sex, age periods, and fuel usage. duration in various age-periods across the adult lifecourse, and Compared with sleeping 8 hours/day on average, 7hours/day risk of lung cancer mortality in Xuanwei, China. An ambidir- was associated with significantly increased HRs ranging from ectional cohort study was conducted in 42,422 farmers from 1.39 to 1.58 in ages 41 years in men, and 1.29 to 2.47 in ages Xuanwei, China. Participants or their surrogates were inter- 51 years in women. Furthermore, sleeping 10 hours/day viewed in 1992 to assess average sleep hours in the age periods was associated with significantly increased HRs ranging from of 21–30, 31–40, 41–50, 51–60, 61–70, and 71 years, which 2.44 to 3.27 in ages 41 year in men, and 1.31 to 2.45 in ages were categorized as 7, 8 (reference), 9, and 10 hours/day. 60 years in women. Greater and less than 8 hours/day of Vital status was followed until 2011. Sex-specificCoxregres- sleep in various age-periods may be associated with elevated sion models were used to estimate hazard ratios (HR) and 95% risk of lung cancer mortality in Xuanwei, China. Cancer Prev Res; confidence intervals (CI) for lung cancer mortality in 1994– 10(6); 327–36. Ó2017 AACR. Introduction tion that focused on lung cancer incidence and mortality in various countries around the world have yielded inconsistent Sleep is characterized by recurrent periods of physical inac- findings (13, 15–20). Taken together, results from previous tivity and augmented neurological activity that are essential for investigations suggest that the intricate relationship between maintaining normal physiological function. Deprivation and sleep duration and lung cancer incidence and mortality may overabundance of sleep have detrimental effects on hormone depend on a variety of factors including sex, age, race/ethnicity, levels, metabolism, and immune function (1–10). Further- and nationality. more, numerous studies found that insufficient and excess Despite its rapid urbanization, nearly 650 million people in sleep were associated with increased risks of cancer-related and China still live in underdeveloped rural communities (21). Xuan- all-cause mortality (11–15). The several studies of sleep dura- wei is one such region that has attracted the attention of global health researchers, as it possesses the highest rates of lung cancer among never-smokers in the country (22). In Xuanwei, lung 1Division of Cancer Epidemiology and Genetics, National Cancer Institute, cancer diagnosis and mortality occurs relatively earlier than other National Institutes of Health, Rockville, Maryland. 2Institute for Risk Assessment Sciences, Division of Environmental Epidemiology, Utrecht University, Utrecht, chronic diseases, with an average age at death from lung cancer of the Netherlands. 3Xuanwei Center of Disease Control No 6, Xuanwei, Qujing, 59–60 years. Therefore, lung cancer mortality constitutes a strong Yunnan, PR China. 4Saw Swee Hock School of Public Health, National University competing risk for death from all other causes, which typically of Singapore and National University Health System, Singapore. 5Department of occur later. In comparison, the average age of lung cancer diag- Medicine, Yong Loo Lin School of Medicine, National University of Singapore and nosis is much later at 70 years in the United States (23). The National University Health System, Singapore. 6Department of Pharmaceutical alarming public health burden of lung cancer in Xuanwei has been Sciences, University of Eastern Piedmont, Novara, Italy. 7College of Public Health Sciences, Chulalongkorn University, Bangkok, Thailand. attributed to indoor air pollution from residential combustion of smoky (bituminous) coal for heating and cooking (24); however, Note: Supplementary data for this article are available at Cancer Prevention fi Research Online (http://cancerprevres.aacrjournals.org/). there is still signi cant variability in lung cancer risk and mortality. Aside from environmental exposures, lifestyle factors such as sleep R.S. Chapman and Q. Lan co-supervised this work. duration may be important contributors. Despite the established Corresponding Author: Jason Y. Wong, National Cancer Institute, 9609 Medical relationships between sleep duration and various health out- Center Drive, Rockville, MD 20850.Phone: 240-176-5149; Fax: 240-276-5149; comes, no large cohort study to our knowledge has focused on E-mail: [email protected] sleep duration across the lifecourse, and its relationship with risk doi: 10.1158/1940-6207.CAPR-16-0295 of lung cancer mortality. The Xuanwei Cohort Study of farmers Ó2017 American Association for Cancer Research. was a unique platform in which to investigate this relationship. www.aacrjournals.org 327 Downloaded from cancerpreventionresearch.aacrjournals.org on October 6, 2021. © 2017 American Association for Cancer Research. Published OnlineFirst April 4, 2017; DOI: 10.1158/1940-6207.CAPR-16-0295 Wong et al. Unlike other studies which evaluated sleep duration in a single This study was approved by the Institutional Review Board of time frame, our study used a unique "lifecourse approach" which the Chinese Academy of Preventive Medicine. Signed informed collected detailed information in various age periods throughout consent was obtained from all literate respondents. Study proce- adulthood in a population with limited circadian disruption. This dures were orally explained to each illiterate individual in the novel "lifecourse approach" provides further etiologic and public presence of a literate relative. If the individual provided oral health insight into the induction time of sleep duration on lung consent, the relative signed the consent form as a surrogate. The cancer mortality. Our study objective was to assess the associa- National Institutes of Health Office of Human Subjects Research tions between average sleep duration in various age periods across (OHSR) determined that federal regulations for the protection of the adult lifecourse, and risk of lung cancer mortality in residents human subjects do not apply to this secondary analysis (Exemp- of Xuanwei, China. tion #5213). Materials and Methods Exposure assessment: average sleep hours across the lifecourse Retrospective sleep data from six age periods were collected in Study design and population sample 1992 via questionnaires or interviews. Participants or their sur- Characteristics of the study population were previously rogates were asked the average number of sleep hours in the age described elsewhere (25, 26). Briefly, participants were sampled periods of 21–30, 31–40, 41–50, 51–60, 61–70, and 71 years. In from four communes in rural Xuanwei, China, including Rong- total, 59% of participants reported their own average sleep hours cheng, Laibin, Jingwai, and Reshui. Local administrative records while 41% were reported by surrogates. Among those alive in were used to identify all residents who were born in 1917–1951 1992, 75% of participants reported their own sleep hours, while and living in the area as of January 1, 1976. Among these residents, the rest was reported by surrogates. Only sleep data from inter- 42,422 individuals were available for the study. The participants views/questionnaires conducted in 1992 were used in this study were predominantly farmers who lived traditional agrarian because age period–specific sleep data were not collected during lifestyles. the follow-ups in 1996 and 2009–2011. An ambidirectional (incident-prevalent) cohort study was con- ducted to assess the associations between average sleep hours in Outcome assessment: lung cancer mortality various age-periods across the lifecourse and risk of lung cancer The outcome of interest was time to death due to lung cancer mortality. This investigation was initiated as a retrospective cohort starting on January 1, 1976. The calendar dates and causes of all study (January 1, 1976–December 31, 1992) and subsequently deaths in the retrospective and prospective study periods extended with two prospective follow-ups in 1996 and 2009– (1976–2011) were extracted from death records. The causes 2011 (Fig. 1). Standardized questionnaires were administered in of death were coded by the Xuanwei Center for Disease Control 1992 by trained interviewers to all participants. Interviews were according to ICD-9 (International Classification of Diseases, directly conducted when feasible (59%), whereas surrogate (next- 9th revision). Death attributed to lung cancer was designated of-kin and close friends) respondents were interviewed when ICD-9 code: 162. individuals were deceased or not present in 1992 (41%). The interviewers collected