Elsevier

Sleep Medicine

Volume 47, July 2018, Pages 36-43
Sleep Medicine

Original Article
Sleep duration on workdays or nonworkdays and cardiac–cerebral vascular diseases in Southern China

https://doi.org/10.1016/j.sleep.2017.11.1147Get rights and content

Highlights

  • This well-designed trial study had a large sample size and standard data collection.

  • This was the first study to assess the association between sleep duration on workdays and nonworkdays and diseases.

  • Abnormal sleep duration was associated with myocardial infarction (MI) and stroke, varying by sex and age.

  • A mismatch in sleep duration between work and nonwork days resulted in greater MI risk.

Abstract

Objectives

This study aimed to assess the relationship between sleep duration on work or nonworkdays and myocardial infarction (MI) and stroke in Southern China.

Methods

A cross-sectional survey was conducted among 15,364 participants of age ≥15 years in Southern China from November 2013 to August 2014. Data on self-reported duration of sleep on workdays or nonworkdays as well as history of MI and stroke were collected in the questionnaire. The subjects were examined for weight, height, waist circumference, and blood pressure. Multivariate logistic regression analyses were performed to evaluate the association of sleep duration with MI and stroke.

Result

Overall, compared with a sleep duration of 6–8 h, individuals who slept <6 h on workdays and nonworkdays were associated with increased risk for MI (odds ratio [OR] = 3.17, 2.04). Furthermore, individuals who slept >8 h on workdays and nonworkdays were associated with an increased risk for stroke (OR = 1.86, 1.54). Although this association persisted in men and subjects aged <65 years, we also observed that long sleep duration on workdays was associated with MI, especially among women, and short sleep duration on nonworkdays was associated with stroke among those aged 65 years or older. Participants with abnormal sleep duration and hypertension had higher risk of MI and stroke. Sleep debt was independently associated with MI risk, but not stroke (OR = 1.40; 95% confidence interval [CI]: 1.06–1.86), specifically among men aged <65 years.

Conclusions

Compared with a sleep duration of 6–8 h, both short and long sleep duration were associated with the prevalence of MI and stroke and these associations were more pronounced among hypertensive persons, and tended to vary by age and sex. Moreover, sleep debt was linked to greater MI risk among men aged <65 years. These findings suggest that we should develop a healthy biological clock.

Introduction

With China's rapid development over the past 30 years, socioeconomic progress has had a great impact on lifestyle. An epidemic of cardiac–cerebral vascular diseases is emerging in China as a result of lifestyle changes, urbanization, and the accelerated process of aging [1], [2]. Among these, myocardial infarction (MI) and stroke are not only well-known causes of death and disability but also public health challenge worldwide. Sleep plays an important role in immunity, particularly in the context of diseases [3]. However, growing numbers of people suffer from sleep disturbance. Therefore, the associations between sleep duration and cardiometabolic diseases and stroke have attracted considerable attention. Growing evidence has indicated that sleep duration is associated with adverse health outcomes including diabetes, cardiovascular disease (CVD), stroke, and all-cause mortality [4], [5], [6], [7], [8], [9]. Findings regarding the link between sleep duration and cardiac–cerebral vascular diseases and the definitions of short and long sleep duration are often inconsistent [10], [11], [12], [13], [14]. Moreover, there is a difference between sleep duration on workdays and nonworkdays. Delays in bedtime, waking time, and mid-sleep time (the midpoint between sleep onset and offset), as well as an increase in sleep duration on nonworkdays compared to that on workdays, have been observed in multiple countries [15], [16], [17], [18]. Previous studies have illustrated social jetlag (SJL)/sleep debt, which is measured as the difference in sleep duration between workdays and nonworkdays and represents the discrepancy between circadian and social clocks, is associated with metabolic risk factors [19], [20], [21]. For instance, Rutters et al. [19] reported that SJL was linked to measures of adiposity, heart rate, and higher cortisol levels in healthy individuals. Wong et al. [20] pointed out that SJL was strongly associated with numerous metabolic risk factors that lead to greater cardiometabolic risk, specifically with components of glycemic control, serum lipids, and adiposity in community dwelling, midlife adults, independently of poor sleep characteristics and health behaviors. However, most studies do not distinguish between sleep duration on workdays and nonworkdays, and very few studies have reported on the association between sleep duration on workdays or nonworkdays and cardiac–cerebral vascular diseases. Therefore, this study aimed to assess the association of sleep duration on workdays or nonworkdays with MI and stroke in Southern China.

Section snippets

Ethics statement

Ethical approval was obtained from the ethics review boards of the Second Affiliated Hospital of Nanchang University and the Fuwai Cardiovascular Hospital (Beijing, China). Written informed consent was obtained from each participant, and the guardians on behalf of the minors/children aged 15–18 years enrolled in the study. If the guardians were unable to write, then fingerprinting was used. The ethics committee approved the procedure.

Study population

The cross-sectional survey was supported by the National Key

Characteristics of the subjects

A total of 15,269 participants out of 15,364 eligible participants (6267 men and 9002 women, aged 15–97 years) were included in the statistical analysis. Overall, the average age was 53.0 ± 17.9. Of those, 7793 (51.0%) participants came from urban areas and 7476 (49.0%) from rural areas. A total of 95 participants were excluded owing to missing data including sex, age, BP, as well as history of MI and stroke. Baseline characteristics are shown in Table 1. The mean (SD) values for sleep duration

Sleep duration and MI and stroke

Previous studies that examined the relationship between sleep duration and CVD and stroke showed inconsistent associations [6], [9], [13], [23], [25], [26], [27], [28], [29]. This included studies that reported an association with cardiac–cerebral vascular diseases for both short and long sleep durations,6, 9, 13or short sleep duration only,23, 29or long sleep duration only [25], [26], [28]. However, in our study, after controlling for similar demographic and potential confounders on workdays

Conclusion

In conclusion, compared with sleep duration of 6–8 h, short and long sleep durations were both associated with the prevalence of MI and stroke, and these associations were more pronounced among patients with HT and tended to vary by age and sex. Sleep debt was associated with greater MI risk among men aged <65 years. These findings suggest that short and long sleep durations may be predictors of cardiac–cerebral vascular diseases, and we should develop a healthy biological clock. Moreover, the

Sources of funding

This research was supported by the National Key R&D Program in the Twelfth Five-year Plan (No. 2011BAI11B01 and 2014ZX09303305) from the Chinese Ministry of Science and Technology and the National Natural Science Foundation of China (No. 81260023 and 81560051).

Financial disclosure

None.

Nonfinancial disclosure

None.

Acknowledgments

We acknowledge the contribution of all staff who participated in this study and the study participants who shared their time with us.

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