Sleep Duration and Mortality

Abstract

I read the paper by Khan et al1Khan H Kella D Kunutsor SK Savonnen K Laukkanen JA Sleep duration and risk of fatal coronary heart disease, sudden cardiac death, cancer death and all-cause mortality.Am J Med. 2018; https://doi.org/10.1016/j.amjmed.2018.07.010Abstract Full Text Full Text PDF Scopus (15) Google Scholar with great interest. The authors conducted a long-term survival study to evaluate the relationship between self-reported sleep duration and risk of fatal coronary heart disease, sudden cardiac death, cancer related death and all-cause mortality. Adjusted hazard ratios (HRs) (95% confidence intervals (CIs)) of long sleep duration (> 10 hours) against sleep duration under 8 hours was 1.19 (1.01-1.43) for all-cause mortality, 1.27 (0.88-1.84) for fatal coronary heart disease, 1.20 (0.78-1.86) for sudden cardiac death, and 1.29 (0.92-1.80) for cancer death, respectively. I present some recent information relating to this study. García-Perdomo et al2García-Perdomo HA Zapata-Copete J Rojas-Cerón CA Sleep duration and risk of all-cause mortality: a systematic review and meta-analysis.Epidemiol Psychiatr Sci. 2018; https://doi.org/10.1017/S2045796018000379Crossref Scopus (21) Google Scholar conducted a meta-analysis on the association between sleep duration and all-cause mortality. The overall risk difference (RD) (95% CI) for all-cause mortality was 0.09 (0.07-0.11) of subjects with sleep duration of >9 hours against sleep duration of 7-9 hours. In contrast, RD (95% CI) for all-cause mortality was 0.00 (0.00-0.01) of subjects with sleep duration of <7 hours against sleep duration of 7-9 hours. They speculated that underlying systemic or neurological diseases may cause sleep fragmentation, deterioration in quality, and micro-awakenings in longer sleepers. Jike et al3Jike M Itani O Watanabe N Buysse DJ Kaneita Y Long sleep duration and health outcomes: A systematic review, meta-analysis and meta-regression.Sleep Med Rev. 2018; 39: 25-36Crossref PubMed Scopus (304) Google Scholar also conducted a meta-analysis on the association between long sleep duration, mortality, and several incidents of metabolic outcomes. Risk ratios (95% CI) of long sleep duration for mortality, incident diabetes mellitus, incident cardiovascular disease (CVD), incident coronary heart disease, incident stroke and incident obesity were 1.39 (1.31-1.47), 1.26 (1.11-1.43), 1.25 (1.14-1.37), 1.46 (1.26-1.69), 1.24 (1.13-1.37) and 1.08 (1.02-1.15), respectively. Although risk of specific mortality was not presented, long sleep duration was a risk factor for mortality and incident metabolic disease. In contrast, Itani et al4Itani O Jike M Watanabe N Kaneita Y Short sleep duration and health outcomes: a systematic review, meta-analysis, and meta-regression.Sleep Med. 2017; 32: 246-256Crossref PubMed Scopus (498) Google Scholar reported that short sleep was also significantly associated with mortality and incident cardiovascular disease. This means that there is a U-shaped relationship between sleep duration, mortality and incident cardiovascular disease. Although attention should be paid to the category of short sleep duration, recent meta-analyses show that both long and short sleep duration are risks for mortality. Finally, Bertisch et al.5Bertisch SM Pollock BD Mittleman MA Buysse DJ Bazzano LA Gottlieb DJ et al.Insomnia with objective short sleep duration and risk of incident cardiovascular disease and all-cause mortality: Sleep Heart Health Study.Sleep. 2018; 41https://doi.org/10.1093/sleep/zsy047Crossref PubMed Scopus (172) Google Scholar conducted a prospective study to investigate the combination effect of insomnia and objective short sleep duration on incident cardiovascular disease and mortality. When insomnia with objective short sleep was defined as sleep problem, propensity score adjusted HR (95% CI) of sleep problem for incident cardiovascular disease was 1.29 (1.00-1.66). But there was no significant association between sleep problem and all-cause mortality. Future studies should address the evaluation method of sleep duration and the combination effect of insomnia and sleep duration on mortality. The ReplyThe American Journal of MedicineVol. 132Issue 1PreviewWe are grateful to the author for his interest in our paper.1 Studies have so far reported a non-linear, almost J-shaped relationship of sleep duration with cardiovascular mortality.2,3 We have extended these findings by ascertaining the relationship of sleep duration with cause specific mortality in a large prospective cohort. A limitation with the existing data on sleep includes poor characterization of the sleep exposure, as a self-reported measure of sleep duration is used. In addition, it does not inform us about the nocturnal vs. Full-Text PDF