Sleep duration and risk of coronary heart disease: A systematic review and meta-analysis of prospective cohort studies
Introduction
Coronary heart disease (CHD), one of the commonest cardiovascular disease, is affecting millions of people in both developed and developing countries [1], [2]. Although the mortality rate of CHD has slightly decreased in developed countries in recently years, it is still the leading cause of death and extorts a heavy social burden in the worldwide [3], [4], [5]. Studies reveal that it may account for about seven million deaths and 129 million loss of disability-adjusted life years (DALYs) annually [6], [7].
A variety of risk factors are identified to be associated with CHD, including genetic and lifestyle factors [8], [9], [10]. In recent years, sleep habit and duration of sleep were reported to play an important role in the onset and progression of CHD [11]. It is estimated that nearly 30% of adults report sleeping less than 6 h per night in western countries [12]. Lack of sleep exerts deleterious effects on metabolic and endocrine systems [13]. Too much or too little sleep are related with several adverse outcomes, including hypertension, type 2 diabetes and poor health [14], [15]. However, as a modifiable lifestyle, sleep could decrease the risk as long as it has been revised.
Several epidemiology studies have found a U-shaped association between sleep duration and CHD [16], [17], [18], but other studies have not report a uniform relationship [19], [20], [21]. For instance, only short sleep duration were found to affect CHD in some studies [22]. A previous meta-analysis also indicated different results for short and long sleep duration [23]. In addition, the study just simply pooled the relative risks of short or long sleep duration group. It remains unknown the exact relationship of sleep duration and CHD. Therefore, we conducted a dose-response meta-analysis of prospective studies to quantify the association between sleep duration and risk of CHD.
Section snippets
Literature search
In accordance with the meta-analysis of observational studies in epidemiology (MOOSE) guidelines [24], we conducted a literature search of PubMed (Medline) and Embase for prospective studies through January 2016 by using the following search terms without restrictions: (“coronary heart diseases”, “CHD”, “cardiovascular disease”, “CVD” “ischemic heart disease”, “myocardial infarction”, “MI”, “angina pectoris”, “angina”, “chest pain”) and (“sleep”). In addition, we also reviewed references from
Literature search
The process of study identification and inclusion was shown in Fig. 1. The search identified 15,897 citations from PubMed and 10,018 citations from Embase prior to 6 January 2016. After 6871 duplicates were excluded, 19,044 citations were remaining for screening through title, abstract, of which 19,023 were excluded because they were cross-sectional studies, case-control studies, or irrelevant studies. After reviewing the full text of these 21 articles, 4 articles [19], [20], [36], [37] were
Discussion
To date, the results of prospective studies on the relationship between sleep duration and risk of CHD have been inconsistent [42], [46], [50]. Several possible reasons are contributed to it, for example, the categories of sleep duration differed across studies [46], [47]. A meta-analysis in 2011 showed both short and long sleep duration were associated with an increased risk of CHD [18], but another one in 2015 just found association between long sleep duration and mortality of CHD, not
Conclusion
In summary, both short and long sleep duration are significantly associated with increased risk of coronary heart disease. Compared with 7 h sleep duration per day, the risk of coronary heart disease increases 11% for an hour decrease and increases 7% for an hour increase. Randomized controlled trials with larger sample sizes and longer follow-up times are warranted to probe the potential mechanisms and to establish causality.
The following are the supplementary data related to this article.
Author contributions
DMW and WHC proposed the study. DMW and WZL performed the searching, data extraction, and quality assessment. XQC, YDM and WHC helped to develop search strategies. DMW, WZL, MZ, and LLX analyzed the data. JXM and GLY provided critical advice. DMW wrote the first manuscript. All authors contributed to reviewing or revising the paper and read and approved the final version.
Funding
The study was supported by the National 111 Project in China (No.B12004) and Innovative Research Team in University of Ministry of Education of China (No. IRT1246). The funder did not play any role in study design; in the collection, analysis, and interpretation of data; in the writing of the report; nor in the preparation, review, or approval of the manuscript.
Conflicts of interest
No conflicts of interest were reported.
Acknowledgements
None.
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