| BackgroundAmbient air pollution,especially atmospheric particulate matter,has been considered as a global health risk factor.In recent years,despite the increasing research on cognitive function of air pollution,the evidence obtained is still limited.In particular,the impact of exposure to PM2 5 on cognitive dysfunction has not been sufficiently substantiated.The results of studies in developed countries such as the United States,Britain,and Germany provide evidence for the relationship between long-term exposure to fine particulate matter and cognitive impairment.However,little is known about the effects of PM2.5 exposure,especially high PM2.5 exposure,on cognitive impairment in the elderly.At present,most researches on the cognitive function of elderly people with atmospheric pollutants are based on cross-sectional surveys,and there are few dynamic changes.Future research will need to find appropriate statistical methods and models to calculate personal exposure and enhance the causality of the argument.At the same time,a large number of longitudinal cohorts and follow-up studies are needed to obtain dynamic data to assess changes in cognitive function and strengthen the causality demonstration.Because of the low level of economic development,developing countries are lagging far behind developed countries in terms of social security and environmental protection.Therefore,we investigate the risk factors that affect the cognitive function of the elderly and the relationship between air pollution and cognitive function,and analyze possible problems.It has far-reaching social significance for solving the health problems such as the pollution and aging in China.MethodsThis study uses longitudinal data from the Chinese Longitudinal Healthy Longevity Survey(CLHLS)from the China Center for Disease Control and Prevention and the Peking University Health Aging and Development Research Center from 2008 to 2011.A total of 9,135 elderly people aged 65 and over participated in the survey.This study mainly includes questionnaire survey and physical measurement.In the questionnaire survey,we collected the potential influence factors of cognitive impairment in the elderly,including social demographic factors,lifestyle,and daily physical activity.Mini-mental State Examination(MMSE)was used to measure cognitive function in the elderly.The MMSE scores ranged from 0 to 30 minutes,24-30 points were normal cognitive function,0-23 points were cognitive impairment.The t test was used to compare the differences in the continuous variables and the chi-square test was used to compare the differences in the categorical variables.Logistic regression model was used to explore the relationship between PM2 5 and cognitive dysfunction.Using main model for further stratification analysis,Variables used for layered analysis do not enter the model.In order to observe the robustness of the model and the results,we performed two sensitivity analyses.First,we re-clear the data and fit the model based on the classification of cognitive impairment in terms of educational level,and observe whether the results are stable.Secondly,taking into account the mortality problem of the elderly population,a sensitivity model was used for sensitivity analysis;the outcome events were divided into cognitive impairment and competition events(death),and competition events were separated from the censored data to test the stability of the result.ResultsIt can be clearly seen that the research area of this study covers the heavily polluted areas in China.The average PM2 5 exposure estimates ranged from 8 to 108?g/m3(52.22±14.31 ?g/m3).Figure 2 illustrated the substantial spatial variability of PM2.5 over the study area from 2008 to 2011.The average age of the study sample at baseline was 79.6 years(range:65-116 years).According to the study design and inclusion and exclusion criteria,a total of 5704 subjects met the inclusion criteria and were followed up successfully,of whom 2946 were males and 2758 were females.A total of 1,408 respondents were lost to follow-up and 2,023 respondents died.Our main model analysis results show that each 10 ?g/m3 increase in PM2.5 concentration was associated increase risk of cognitive impairment incidence(RR:1.06;95%CI:1.01-1.11).Sensitivity analysis results showed that when increasing or deleting some possible confounding factors and replaces the analysis method,the results remain stable.All of the above sensitivity analyses showed that the relationship between PM2.5 and cognitive impairment incidence in this study was stable.Subgroup analysis suggested that the association between PM2.5 and cognitive impairment incidence was affected by age,sex,smoking,body mass index,place of residence,and hypertension.PM2.5 concentration was associated with increased risk of cognitive impairment incidence among man(RR:1.11;95%CI:1.04-1.19),current smoker(RR:1.10;95%CI:1.02-1.19),hypertension patient(RR:1.08;95%CI:1.01-1.16),live in urban areas(RR:1.07;95%CI:1.01-1.16),underweight(RR:1.10;95%Cl;1.01-1.19)and participants aged>80years(RR:1.10;95%CI:1.03-1.18).It shows that the incidence of cognitive impairment in high-age group,male,low-weight,current smoking,hypertension,and people living in cities have more sensitive trends to PM2.5.ConclusionTo our best knowledge,this is the first well-defined prospective cohort study to investigate the high exposure of PM2.5 and cognitive impairment among a national wide elderly in China.In this study,exposure to PM2 5(8-108?g/m3)was associated with higher incidence of cognitive impairment after accounting for potential confounders.Each 10?g/m3 increase in PM2.5 concentration was associated with a 6%increase in the risk of cognitive impairment.The effect is especially significant in men,current alcohol drinker,current smoker,the elder age group and hypertensive patients.This study added existing evidence on air pollution and the incidence of cognitive impairment among elderly in China,a high exposure of PM2 5 area. |
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