title: Sleep duration and risk of all-cause mortality: A flexible, non-linear, meta-regression of 40 prospective cohort studies.
abstract: Approximately 27-37% of the general population experience prolonged sleep duration and 12-16% report shortened sleep duration. However, prolonged or shortened sleep duration may be associated with serious health problems. A comprehensive, flexible, non-linear meta-regression with restricted cubic spline (RCS) was used to investigate the dose-response relationship between sleep duration and all-cause mortality in adults. Medline (Ovid), Embase, EBSCOhost-PsycINFO, and EBSCOhost-CINAHL Plus databases, reference lists of relevant review articles, and included studies were searched up to Nov. 29, 2015. Prospective cohort studies investigating the association between sleep duration and all-cause mortality in adults with at least three categories of sleep duration were eligible for inclusion. We eventually included in our study 40 cohort studies enrolling 2,200,425 participants with 271,507 deaths. A J-shaped association between sleep duration and all-cause mortality was present: compared with 7 h of sleep (reference for 24-h sleep duration), both shortened and prolonged sleep durations were associated with increased risk of all-cause mortality (4 h: relative risk [RR] = 1.05; 95% confidence interval [CI] = 1.02-1.07; 5 h: RR = 1.06; 95% CI = 1.03-1.09; 6 h: RR = 1.04; 95% CI = 1.03-1.06; 8 h: RR = 1.03; 95% CI = 1.02-1.05; 9 h: RR = 1.13; 95% CI = 1.10-1.16; 10 h: RR = 1.25; 95% CI = 1.22-1.28; 11 h: RR = 1.38; 95% CI = 1.33-1.44; n = 29; P < 0.01 for non-linear test). With regard to the night-sleep duration, prolonged night-sleep duration was associated with increased all-cause mortality (8 h: RR = 1.01; 95% CI = 0.99-1.02; 9 h: RR = 1.08; 95% CI = 1.05-1.11; 10 h: RR = 1.24; 95% CI = 1.21-1.28; n = 13; P < 0.01 for non-linear test). Subgroup analysis showed females with short sleep duration a day (<7 h) were at high risk of all-cause mortality (4 h: RR = 1.07; 95% CI = 1.02-1.13; 5 h: RR = 1.08; 95% CI = 1.03-1.14; 6 h: RR = 1.05; 95% CI = 1.02-1.09), but males were not (4 h: RR = 1.01; 95% CI = 0.96-1.06; 5 h: RR = 1.02; 95% CI = 0.97-1.08; 6 h: RR = 1.02; 95% CI = 0.98-1.06). The current evidence suggests that insufficient or prolonged sleep may increase all-cause mortality. Women may be more susceptible to short sleep duration on all-cause mortality.
authors.affiliation: Department of Urology, Zhongnan Hospital of Wuhan University, Wuhan University, Wuhan, China; Center for Evidence-Based Medicine, Wuhan University, Wuhan, China. Electronic address: Liutongzu@163.com.
authors.forename: Tong-Zu
authors.initials: TZ
authors.lastname: Liu
authors.affiliation: Department of Urology, Zhongnan Hospital of Wuhan University, Wuhan University, Wuhan, China; Center for Evidence-based Medicine and Clinical Research, Taihe Hospital, Hubei University of Medicine, Shiyan, China.
authors.forename: Chang
authors.initials: C
authors.lastname: Xu
authors.affiliation: Department of Epidemiology, IRCCS - Istituto di Ricerche Farmacologiche Mario Negri, Via G. La Masa 19, 20156 Milan, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Rota
authors.affiliation: Vanderbilt Epidemiology Center, Department of Medicine and Vanderbilt-Ingram Cancer Center, Nashville, United States.
authors.forename: Hui
authors.initials: H
authors.lastname: Cai
authors.affiliation: Center for Evidence-based Medicine and Clinical Research, Taihe Hospital, Hubei University of Medicine, Shiyan, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Zhang
authors.affiliation: The French National Center for Scientific Research, UMR 144, Institute Curie, 75248 Paris, France.
authors.forename: Ming-Jun
authors.initials: MJ
authors.lastname: Shi
authors.affiliation: Department of Epidemiology and biostatistics, School of public health, Wuhan University and global health institute, Wuhan University, Wuhan, China.
authors.forename: Rui-Xia
authors.initials: RX
authors.lastname: Yuan
authors.affiliation: Department of Urology, Zhongnan Hospital of Wuhan University, Wuhan University, Wuhan, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Weng
authors.affiliation: Center for Evidence-Based Medicine, Wuhan University, Wuhan, China.
authors.forename: Xiang-Yu
authors.initials: XY
authors.lastname: Meng
authors.affiliation: Chinese Evidence-Based Medicine Center, Chinese Cochrane Center, West China Hospital, Sichuan University, Chengdu, China; Center for Evidence-based Medicine and Clinical Research, Taihe Hospital, Hubei University of Medicine, Shiyan, China. Electronic address: jswkwong@hotmail.com.
authors.forename: Joey S W
authors.initials: JS
authors.lastname: Kwong
authors.affiliation: Chinese Evidence-Based Medicine Center, Chinese Cochrane Center, West China Hospital, Sichuan University, Chengdu, China. Electronic address: sunx79@hotmail.com.
authors.forename: Xin
authors.initials: X
authors.lastname: Sun
mesh_terms: D006801:Humans; D009026:Mortality / Q000639:trends; D012307:Risk Factors; D012737:Sex Factors; D012893:Sleep Wake Disorders / Q000401:mortality; D013997:Time Factors
keywords: All-cause mortality; Dose–response relationship; Meta-analysis; Sleep duration