Association Of Indoor Solid Fuel Use With Depressive Symptoms And Cognitive Function In Middle-Aged And Elderly People

Objective Based on longitudinal data from the China Health and Retirement Longitudinal Study（CHARLS）,we investigated the longitudinal association between indoor use of solid fuels and depressive symptoms and cognitive function in the middle-aged and elderly population to gain insight into the effects of indoor air pollution on mental health and cognitive function in the middle-aged and elderly population.To explore the possible causal relationship between depressive symptoms and cognitive impairment in the middle-aged and elderly population,and to provide a scientific basis for improving the mental health and quality of life of the middle-aged and elderly population in China in a targeted manner.Methods The data for this study were obtained from the CHARLS National Follow-Up Survey.The study population was the middle-aged and elderly population aged 45 years and above,and the subjects of this study were selected according to certain inclusion and exclusion criteria.A descriptive epidemiological approach was used to analyse the prevalence and distribution of depression and cognitive dysfunction in middle-aged and older adults.A linear mixed-effects model was used to investigate the association between indoor solid fuel use and the 10 Items Center for Epidemiologic Studies Depression Scale（CES-D10）scores,total cognitive scores,and cognitive dimension scores;a cross-lagged Panel models were used to explore the inter-predictive relationships between CES-D10 scores,total cognitive scores,and cognitive dimension scores.Results 1.Study of the association between indoor solid fuel use and depressive symptoms in middle-aged and older adults:A total of 4745 subjects were included in this study at baseline,and the prevalence of depression in the study population was38.72%at the 2011 baseline survey and the cumulative prevalence of depression from2011-2015 was 33.05%.Compared to study participants who cooked with clean fuels,the cooking with solid fuels group had a higher risk of depression onset（HR:1.21,95%CI:1.08-1.35）,a higher CES-D10 score（β=0.30,P<0.001）and a faster rise in their CES-D10 score with increasing unit time（every 2 years）（β=0.14,P<0.001）.The risk of depression was higher in the group using solid fuels for heating（HR:1.33,95%CI:1.16-1.52）,with a higher CES-D10 score（β=0.37,P<0.001）,and increased more rapidly with unit time（every 2 years）than in the study participants using clean fuels for heating（β=0.10,P<0.05）.Compared to study participants who cooked and heated with both clean fuels,one of the solid fuel groups had a higher risk of depression（HR:1.27,95%CI:1.08-1.49）and a higher CES-D10 score（β=0.27,P<0.05）;both solid fuel groups had a higher risk of depression（HR:1.43,95%CI:1.23-1.67）,had higher CES-D10 scores（β=0.50,P<0.001）,and their CES-D10 scores rose more rapidly with increasing unit time（every 2 years）（β=0.15,P<0.05）.The risk of depression was higher in the group that switched from clean to solid fuels for cooking（OR:1.35,95%CI:1.05-1.76）and in the group that switched from clean to solid fuels for heating（OR:1.43,95%CI:1.01-2.02）compared to the study participants who had been using clean fuels.2.Study of the association between indoor solid fuel use and cognitive function in middle-aged and older adults:A total of 4778 baseline study subjects were included in this study,with a baseline prevalence of cognitive dysfunction of 16.58%in 2011 and a cumulative prevalence of cognitive dysfunction of 19.19%in the study population from 2011-2015.The group using solid fuels for cooking had a higher risk of developing cognitive dysfunction（HR:1.32,95%CI:1.12-1.55）,a lower cognitive score（β=-0.35,P<0.001）,and a higher risk of developing cognitive impairment（HR:1.32,95%CI:1.12-1.55）and a lower score on the Telephone Interview of Cognitive Status（TICS）scale compared to the study participants using clean fuels for cooking.Status（TICS）scale（β=-0.30,P<0.001）,worse visuospatial ability（β=-0.19,P<0.05）,and a faster decline in cognitive scores（β=-0.06,P<0.05）and memory scores（β=-0.05,P<0.001）with increasing unit time（every 2 years）.Changes in TICS scores,visuospatial ability were not statistically different（P>0.05）.Compared to subjects who used clean fuels for heating,the group using solid fuels for heating had a higher risk of developing cognitive dysfunction（HR:1.35,95%CI:1.12-1.62）,lower cognitive scores（β=-0.41,P<0.001）,lower memory scores（β=-0.11,P<0.05）,lower TICS scores（β=-0.26,P<0.001）,and worse performance in visuospatial ability（β=-0.37,P<0.001）,with no statistical difference（P>0.05）in the decrease in cognitive scores,memory scores,TICS scores,and visuospatial ability as the unit time increased（every 2 years）.Compared to study participants who cooked and heated with clean fuels,one of the solid fuel groups had a higher risk of developing cognitive dysfunction（HR:1.68,95%CI:1.23-2.28）,lower cognitive scores（β=-0.34,P<0.05）,lower memory scores（β=-0.18,P<0.05）and poorer performance in visuospatial ability（β=-0.42,P<0.05）,and TICS scores were not statistically different（P>0.05）;the decrease in cognitive scores,memory scores,and visuospatial abilities were not statistically different（P>0.05）with increasing unit time（every 2 years）,and TICS scores decreased more rapidly（β=-0.07,P<0.05）;the risk of morbidity was higher in the group using solid fuels for both cooking and heating（HR:2.05,95%CI:1.43-2.95）,lower cognitive scores（β=-0.58,P<0.001）,lower memory scores（β=-0.13,P<0.05）,lower TICS scores（β=-0.40,P<0.001）,and worse visuospatial performance（β=-0.42,P<0.001）,with unit The decrease in cognitive scores was faster in the group that used solid fuels all the time（every 2 years）（β=-0.07,P<0.05）,and the decrease in memory scores,TICS scores,and visuospatial abilities were not statistically different（P>0.05）.The risk of cognitive dysfunction was higher in the group that switched from clean to solid fuels for heating（OR:2.36,95%CI:1.57-3.56）compared to the study participants who had been using clean fuels.3.Causal association between depressive symptoms and cognitive function in middle-aged and elderly people:using the cognitive score Q1 group as a control group,the risk of depression onset was lower in the cognitive score Q3 and Q4 groups（HR:0.75,95%CI:0.62-0.88;HR:0.59,95%CI:0.48-0.72）and gradually decreased with increasing cognitive score(P_trend<0.05).Using the CES-D10 score Q1 group as a control group,the risk of developing cognitive dysfunction was higher in the CES-D10score Q3 and Q4 groups（HR:1.32,95%CI:1.09-1.59;HR:1.58,95%CI:1.29-1.92）,and the risk of developing cognitive dysfunction gradually increased as the CES-D10score increased(P_trend<0.001).The results of the cross-lagged panel model analysis showed that the pre-test values of CES-D10 scores all significantly predicted the post-test values of total cognitive scores,memory scores and TICS scores,and the pre-test values of total cognitive scores,memory scores and TICS scores all significantly predicted the post-test values of CES-D10 scores.Conclusions 1.Indoor use of solid fuels increases the risk of depression in middle-aged and older people.People who switch their indoor cooking and heating fuels from clean to solid fuels may be at higher risk of depression,and indoor use of solid fuels is associated with higher CES-D10 scores in middle-aged and older people,with faster increases in CES-D10 scores in those who use solid fuels.2.Indoor use of solid fuels increases the risk of cognitive impairment in middle-aged and older adults,and those who switch their indoor heating fuel from clean to solid fuels may be at higher risk of cognitive impairment.3.There may be a bidirectional causal association between depressive symptoms and cognitive impairment in middle-aged and elderly populations.The risk of developing cognitive impairment was higher in the high CES-D10 score group at baseline and the risk of developing depression was higher in the high cognitive score group at baseline,and there was a bidirectional predictive relationship between CES-D10 scores and total cognitive scores,memory scores and TICS scores in the middle-aged and elderly population.