Associations Of Sleep Duration And Sleep Quality With Risk Of Incident Stroke In Middle-aged And Older Adults

Stroke has become the first cause of death and disability in Chinese adults,causing a huge disease burden for our country.Traditional risk factors including cigarette smoking,alcohol drinking,physically inactivity,hypertension,diabetes mellitus,and obesity have been confirmed to be associated with the risk of stroke.Sleep,an important lifestyle factor,has been found in associations with multiple health outcomes including stroke.Growing epidemiological evidence suggested that short or long sleep duration was associated with increased risk of stroke.However,most of previous studies were conducted among European or American populations and the results remained controversial.Moreover,few studies have investigated the associations of sleep duration with risk of incident stroke subtypes.To date,most of the existing studies on the association of sleep duration with stroke risk in Chinese population are cross-sectional or case-control studies;large prospective cohort studies remain scarce.Additionally,most previous studies have investigated the association of sleep duration with stroke risk regardless of midday napping,which is a common practice in China.The association of midday napping with stroke risk remains to be elucidated.Furthermore,the effect of sleep quality on incident stroke and whether sleep quality modifies the association of sleep duration with incident stroke or not remain unclear.Therefore,we aimed to investigate the associations of sleep duration and sleep quality with the risk of incident stroke and stroke subtypes.Firstly,we carried out a cross-sectional study to explore factors associated with nighttime sleep duration,midday napping and sleep quality among middle-aged and older Chinese;Secondly,we prospectively investigated the associations of nighttime sleep duration,midday napping and sleep quality with the risk of incident stroke and stroke subtypes;Lastly,we performed a Mendelian Randomization study to evaluate the causal association of nighttime sleep duration with stroke risk among middle-aged and older Chinese.As described below,this paper includes three main parts.Part? Factors associated with Nighttime Sleep Duration,Midday Napping and Sleep Quality in Middle-aged and Older ChineseObjectives:To explore the associations of major lifestyles and occupational factors with nighttime sleep duration,midday napping and sleep quality among middle-aged and older Chinese.Methods:We used data from the Dongfeng-Tongji cohort.A total of 32324 participants without stroke,coronary heart disease(CHD),cancer or missing information related to sleep duration were included in the study.Polynomial logistic regression models were applied to investigate the associations of demographic characteristics,socioeconomic status,major lifestyles,and occupational factors with nighttime sleep duration and midday napping.Logistic regression models were used to investigate factors associated with sleep quality.By calculating change in nighttime sleep duration between baseline and the first follow-up survey,we further explored factors associated with 5-year change in nighttime sleep duration in 17879 subjects who have completed both the baseline and first follow-up surveys and without CHD,stroke,cancer or missing information related to sleep duration.Results:The mean nighttime sleep duration was 8.09±1.02 h.Among the 32324participants,23.86%reported sleeping?9 h/night;62.23%reported a habit of midday napping and 7.61%reported midday napping>90 min;and 11.22%reported poor sleep quality.Male and being unmarried were positively associated with long nighttime sleep duration(?9 h/night),whereas,higher education level and regular exercise were negatively associated with long nighttime sleep duration.For midday napping,male,higher BMI(?24 kg/m²),current drinking,current smoking,and hypertension were associated with increased ORs for long midday napping(>90 min),whereas,higher education level and regular exercise were associated with decreased ORs for long midday napping.Moreover,female,being divorced/widowed,diabetes and hyperlipidemia and shift work were positively associated with poor sleep quality;nevertheless,regular exercise was negatively associated with poor sleep quality.Furthermore,current smoking,age?65 years,and being divorced/widowed were associated with 5-year increase in nighttime sleep duration;however,higher education level was negatively associated with prolonged nighttime sleep duration over 5 years.Conclusions:In this large population-based study,we found that gender,BMI,education level,marital status,smoking,drinking and regular exercise were closely related to nighttime sleep duration and midday napping among middle-aged and older Chinese.Female,being divorced or widowed,diabetes mellitus,hyperlipidemia and history of shift work were associated with poor sleep quality among middle-aged and older Chinese.Part? Associations of Nighttime Sleep Duration,Midday Napping and Sleep Quality with Incident Stroke:A Prospective Cohort StudyObjectives:Epidemiological evidence suggested that shorter or longer sleep duration was associated with an elevated risk of stroke.However,their results indicated a J-shaped or U-shaped curve or null for the relationship and remained controversial.Moreover,few studies investigated the associations of sleep duration with incident stroke subtypes.Furthermore,the effects of midday napping and sleep quality on incident stroke and stroke subtypes remain to be elucidated.Based on the Dongfeng-Tongji cohort,we aimed to prospectively investigate the associations of nighttime sleep duration,midday napping and sleep quality with the risk of incident stroke and stroke subtypes.We further explored the association of longitudinal change in nighttime sleep duration with subsequent stroke risk among middle-aged and older Chinese adults.Methods:We used data from the Dongfeng-Tongji cohort.After excluding participants with CHD,stroke,or cancer at baseline and those who were lost to follow-up or with missing information on sleep duration,a total of 31750 subjects were included in the present study.The outcome of interest was incident stroke.All participants were followed up to December 31st,2016.We used Cox proportional hazard regression models to estimate hazard ratios(HRs)and 95%confidence intervals(CIs)for the associations of nighttime sleep duration,midday napping and sleep quality with incident stroke and stroke subtypes.Furthermore,we investigated the association of longitudinal change in nighttime sleep duration with subsequent risk of incident stroke in a subgroup of subjects who reported nighttime sleep duration at both baseline and the first follow-up surveys,and without preexisting CHD,stroke or cancer by the date of first follow-up survey in2013(n=15624).Results:Compared with participants sleeping 7-<8 h/night,those reporting longer nighttime sleep duration(?9 h/night)had a greater risk of total stroke(HR,1.23;95%CI,1.07-1.41),while shorter nighttime sleep duration(<6 h/night)had no significant effect on stroke risk.When stratified by stroke subtypes,similar associations were observed between?9 h/night of sleep and ischemic stroke,but not hemorrhagic stroke.The HR(95%CI)of total stroke was 1.25(1.03-1.53)for midday napping>90 min vs 1-30 min.The significant association was also observed between midday napping>90 min and ischemic stroke,but not hemorrhagic stroke.Compared with participants with good sleep quality,those with poor sleep quality showed a 29%,28%and 56%higher risk of total,ischemic,and hemorrhagic stroke,respectively.Moreover,we observed significant joint effects of sleeping?9 h/night and midday napping>90 min(HR,1.85;95%CI,1.28-2.66),and sleeping?9 h/night and poor sleep quality(HR,1.82;95%CI,1.33-2.48)on risks of total stroke.Furthermore,compared with persistently sleeping 7-9 h/night,those persistently slept?9 h/night or switched from 7-9 h to?9 h/night of sleep showed a 35%(HR,1.35;95%CI,1.01-1.82)and 44%(HR,1.44;95%CI,1.12-1.86)higher risk of total stroke.Conclusions:Long nighttime sleep duration(?9 h/night)and long midday napping(>90min)were associated with higher risk of incident stroke,particularly for ischemic stroke.Poor sleep quality increased the incident risk of total stroke and also ischemic and hemorrhagic stroke separately.Significant joint effects of nighttime sleep duration and midday napping,nighttime sleep duration and sleep quality were observed on the risk of stroke.Additionally,persistently long nighttime sleep duration or switch from average to long nighttime sleep duration were associated with higher subsequent stroke risk.Our results highlight the importance of appropriate and stable nighttime sleep duration,moderate midday napping and maintaining good sleep quality for stroke prevention,especially in middle-aged and older adults.Part? Association of Nighttime Sleep Duration with Incident Stroke:A Mendelian Randomization StudyObjectives:Prospective studies indicated that long sleep duration was associated with an elevated risk of incident stroke.However,whether there is a causal association between sleep duration and incident stroke remains largely unknown.Based on the Dongfeng-Tongji cohort study,we conducted a Mendelian randomization(MR)study to explore the causal relationship between nighttime sleep duration and incident stroke.Methods:A total of 7375 participants without cancer or missing information on sleep duration were included in the MR study.We selected SNPs associated with sleep duration as instrumental variables based on the results of genome-wide association study(GWAS)on nighttime sleep duration conducted in the Dongfeng-Tongji cohort and SNPs published in previous studies.Genetic risk score(GRS)and the inverse-variance weighting(IVW)methods were applied to investigate whether there is a causal relationship between nighttime sleep duration and incident stroke.Results:The GWAS study based on 7572 middle-aged and older Chinese identified a total of 14 loci associated with nighttime sleep duration(P?5×10^-6).Moreover,based on previously published GWAS studies,we chose 6 SNPs associated with sleep duration.Thus,a total of 20 SNPs were selected as instrumental variables in the MR study.Neither the GRS nor the IVW method found significant associations of nighttime sleep duration with the risk of incident stroke(Weighted GRS:OR,0.97;95%CI,0.71-1.32;IVW:OR,0.97;95%CI,0.72-1.31).Conclusions:Probably due to the relatively small sample size in the present MR study,we did not find a causal relationship between nighttime sleep duration and stroke incidence.Whether there is a causal relationship between nighttime sleep duration and incident stroke needs to be further verified in a larger and more representative population.