A Study On The Relationship Between The Sleep Quality Of The Community-dwelling Elderly Population And Cognitive Function,and Its Relevant Factors

Background With the gradual aging of the population,the conditions of the elderly population may change,especially in the aspect of cognitive function and sleep status.It is well known that sleep disorders have always been a public health concern in developing and developed countries;these disorders also play an important role in the development of cognitive impairment.Therefore,a better understanding of the association between sleep and cognitive function can help us identify the population with a high risk for cognitive impairment.However,few studies involving sleep and cognitive function assessed sleep quality in a qualitative and quantitative fashion,and most studies only involved the relationship between sleep duration and cognitive function.Meanwhile,there is also a lack of studies on the association between sleep duration and quality in combination and cognitive function,as well as studies involving stratification by gender and age.In addition,the mediating effect of depressive status on the association between sleep quality and duration and cognitive function in the community population has been rarely reported.Objective This study aims to:(1)explore the status quo of sleep of elder people aged 60 years and above and identify its influencing factors,so as to analyze the epidemiological association between sleep quality and cognitive function using cross-sectional data;(2)explore the influence of depressive status on sleep quality,sleep duration and cognitive function,in order to provide scientific basis for relevant prevention strategies.Methods1.On the basis of Disease Spectrum of Community Residents and Environmental Factors in 2018,we conducted an epidemiological investigation on the sleeping status of the elderly population aged 60 years and above,in order to analyze their sleeping status,distributional characteristics in the population,and influencing factors.2.Pittsburgh sleep quality index(PSQI)was used to quantify sleep quality and assess subjective sleep disorders,with higher PSQI scores indicating poorer sleep quality.Mini-Mental State Examination(MMSE)was used to assess cognitive impairment,with the total score being an analysis index.Depression status was assessed using the Chinese version of 15-item Geriatric Depression Scale(GDS-15),with higher scores indicating more severe depression status.Multivariate logistic regression analysis was used to analyze the association of sleep duration and quality with cognitive impairment,with sleeping status(sleep duration,sleep quality)as the independent variable and the presence of cognitive impairment as the dependent variable(with individuals with normal cognitive function as the reference group).Restricted cubic spline was used to analyze the relationship of sleep duration and continuous sleep quality index with cognitive impairment.First,using the sleep duration of 7~<8 hours(normal sleep duration)as a reference,we analyzed the association between different sleep durations and cognitive impairment.Second,the association between overall sleep quality(good/poor,with PSQI >7 defined as poor sleep quality)and cognitive impairment was analyzed.Third,the association between the total score of Pittsburgh sleep quality index(PSQI)as well as the score of each factor(except for sleep duration)and cognitive impairment was analyzed.Fourth,the association between sleep duration and quality in combination and cognitive impairment was analyzed.In addition,the association between the sleep status of different gender subgroups and age subgroups and cognitive impairment was also further explored.3.On the basis of the above researches,explored whether depressive status had a mediating effect on the association between sleep duration and quality and cognitive impairment,with the use of PROCESS program developed by Andrew Hayes for SPSS software.Results1.Investigation and analyses of the status quo of sleep in the elderly population and its relevant factors1.1 General information of the study population The study included 4,837 elderly people aged ≥60 years.Their age ranged 60-97 years,with a mean of 71.13±5.50 years.Male subjects accounted for 48.9% and female subjects accounted for 51.1%.The overall PSQI score was 6.69±3.66.The detection rate of poor sleep quality in the elderly population was 36.3%.1.2 Univariate analysis of sleep quality in the elderly population(1)Regarding demographic factors,the detection rate of poor sleep quality in females is higher than that in males(43.1% vs.29.2%,P <0.001).Other influencing factors(P<0.05)included level of education,marital status,living mode,and financial situation.(2)Among living and behavioral factors,the influencing factors(P <0.05)fresh fruits,eggs and egg products,drinking status,smoking status,and physical exercises.Gender stratification showed that the drinking or smoking status of males or females did not have statistically significant influence on the sleep quality(P >0.05).(3)Among health-related factors,the influencing factors(P <0.05)included healthy body fat percentage,diabetes,hypertension,coronary heart disease,stroke,activities of daily living,and depressive status.1.3 Multivariate logistic regression analysis of the sleep quality of the elderly population The result showed that the sleep quality of elderly people was much more affected by gender(the risk in females was 1.999 times that in males),especially in women at advanced ages(81-97 years).Protective factors for good sleep quality included having fresh fruits and eggs or egg products daily or almost daily.Being married is also a protective factor for good sleep quality in elderly people.Risk factors for poor sleep quality included coronary heart disease,daily living dysfunction,and depressive state;being a current or former smoker is also a risk factor for people at an advanced age.2.Association analyses between the sleep status of elderly people and cognitive function2.1 Univariate analysis of cognitive impairment in the elderly population In this study,a total of 1,811 subjects had cognitive impairment,with an overall detection rate of 37.4%;among them,females accounted for 42.3% and males accounted for 32.3%.The detection rate of cognitive impairment in subjects with poor sleep quality was 42.6%,while the detection rate in those with good sleep quality was lower,which was 为 34.5%;the detections rate of cognitive impairment in those with a sleep duration of 7~<8 hours was also relatively low,which was 31.8%.Moreover,the subjects’ cognitive function was also affected by the type of household,level of education,occupation,marital status,mode of living,financial status,staple food,fresh fruits,eggs and egg products,dairy products,drinking status,smoking status,physical exercises,exercise intensity,hypertension,coronary heart disease,activities of daily living,and depressive status.2.2 Correlation analysis between the sleep status of elderly people and cognitive impairment2.2.1 Correlation analysis between the sleep duration of elderly people and cognitive impairment The logistic regression model showed that,in the final model adjusted for confounding factors,the risk for cognitive impairment in subjects with short sleep duration,those with relatively short sleep duration and those with relatively long sleep duration was 1.34(95% CI:1.08-1.66),1.39(95% CI:1.13-1.73),and 1.31(95%CI:1.06-1.61)times that in those with normal sleep duration.In male subjects,the risk for cognitive impairment in subjects with short sleep duration,those with relatively long sleep duration and those with long sleep duration was 1.44(95% CI:1.05-1.99),1.47(95% CI:1.09-1.98),and 1.47(95% CI:1.07-2.02)times that in those with normal sleep duration;while in female subjects,only those with relatively short sleep duration had a risk for cognitive impairment 1.42(95%CI:1.06-1.90)times that in those with normal sleep duration.For different age groups,the risk for cognitive impairment in subjects aged 60-70 years who had short sleep duration,relatively short sleep duration and relatively long sleep duration was1.58(95%CI:1.17-2.13),1.52(95%CI:1.13-2.05),and 1.64(95%CI:1.20-2.23)times that in those with normal sleep duration;but for subjects aged 71-80 years,only those with relatively short sleep duration had a risk for cognitive impairment 1.45(95%CI:1.03-2.04)times that in those with normal sleep duration.2.2.2 Correlation analysis between the sleep quality of elderly people and their cognitive impairment The logistic regression model showed that,in the final model adjusted for confounding factors,the risk for cognitive impairment in subjects with poor sleep quality was 1.27(95%CI : 1.10-1.47)times that in those with good sleep quality.Among PSQI continuous variables,only the overall PSQI score,sleep latency,and daytime dysfunction had significant influence on cognitive impairment.In gender subgroups,the risk of cognitive impairment in female subjects with poor sleep quality was 1.31(95%CI:1.07-1.60)times that in those with good sleep quality,and the total score and all the factor scores(sleep latency and daytime dysfunction)of PSQI for female subjects had a strong effect(P <0.05)on cognitive impairment.For different age groups,the risk for cognitive impairment in 60-70-year-old subjects with poor sleep quality was 1.34(95%CI:1.09-1.64)times that in those with good sleep quality,while in subjects aged 81-97 years,only sleep disorder had a strong influence on cognitive impairment(P=0.011).2.2.3 Correlation analysis between the sleep duration and sleep quality in combination and cognitive impairment In the final model adjusted for confounding factors,as compared with those with normal sleep and good sleep quality,subjects with the following combination had higher risk for cognitive impairment(P <0.05): short sleep duration and good sleep quality,relatively long sleep duration and good sleep quality,long sleep duration and good sleep quality,short sleep duration and poor sleep quality,relatively short sleep duration and poor sleep quality,and normal sleep duration and poor sleep quality.It should be noted that subjects with relatively long sleep duration and poor sleep quality(OR: 2.56,95% CI: 1.52-4.33)and those with long sleep duration and poor sleep quality(OR: 1.96,95% CI: 1.04-3.69)were more significantly associated with cognitive impairment.3.Influence of depressive status on the sleep quality,sleep duration,and cognitive function3.1 Mediating effect of depressive status on sleep quality and cognitive function The result showed that sleep quality had a significant negative correlation effect on cognitive function(β=-0.065,t=-4.562,p<0.001);with the mediator variable,i.e.,depressive status,fitted in,the negative correlation effect of sleep quality on cognitive function was still significant(β=-0.042,t=-2.896,p<0.01).In addition to directly predicting cognitive function,sleep quality could also predict cognitive function through the mediating effect of depression;the direct and indirect effect values were-0.04 and-0.023,with indirect effect accounting for 35.38% of the total effect.3.2 Mediating effect of depressive status on sleep duration and cognitive function With the mediator variable(depressive status)fitted in,the sleep duration had a significant negative correlation effect on cognitive function(β=-0.028,t=-2.038,p<0.05).The negative correlation effect of sleep duration on depressive status was significant(β=-0.145,t=-9.793,p<0.001),and the negative correlation effect of depression status on cognitive function was also significant(β=-0.114,t=-8.059,p<0.001).The 95% confidence interval of the total effect was(-0.039-0.015),which included 0,indicating that the indirect effect of depressive status on sleep duration and cognitive function was suppressing effect,suggesting that the indirect effect of depressive status on the association between sleep duration and cognitive function led to the insignificant total effect of sleep duration and cognitive function.Conclusion1.The overall sleep quality of the elderly population in this region in Anhui Province was relatively poor,and it was affected by gender;the sleep quality in female subjects was poorer than male subjects in all age groups,which was more remarkable in females at an advanced age.Sleep quality was also affected by their diets,marital status,health-related factors,etc.2.The detection rate of cognitive impairment in the elderly population in this region in Anhui Province was relatively high,and was affected by sleep duration and sleep quality in combination.Normal sleep duration and good sleep quality showed the strongest association with optimal cognitive performance.Moreover,there were also gender and age differences regarding the association between sleep duration and quality and cognitive impairment.3.Sleep quality and sleep duration could affect cognitive function through the mediation of depressive status.