| Objective: Socioeconomic status(SES),as a multidimensional concept,is composed of diverse indicators that reflect different aspects of it and may have different effects on health at different times in the life course.However,previous studies on SES and cognitive impairment were mainly conducted in foreign countries,and there is a lack of evidence in developing countries such as China.Besides,some studies have found that leisure activities were not only affected by SES,but also related to cognitive impairment.Here,we based on 13-year prospective research data and constructed two comprehensive indicators of SES in childhood and adulthood to assess the relationships between life course SES and cognitive impairment,and to explore the mediating effect of leisure activities in the above-mentioned relationships.Metohds: Data was collected from the Chinese Longitudinal Healthy Longevity Survey(CLHLS)and we selected participants aged 65 years and older without cognitive impairment at baseline(2005)and participated in a follow-up survey(2008-2018)in this study.Cognition function was measured using the Chinese version of the Mini-Mental State Examination(MMSE),and we used education-based MMSE cutoff points to define cognitive impairment.The SES consisted of two different life stages: childhood SES and adult SES.Childhood SES included 5 domains,ie.,place of birth,medical services at childhood,went to bed without hunger at childhood,both parents were alive when the participant was age 10 and father’s occupation at childhood.Meanwhile,adult SES included 3 domains,ie.,place of residence,education level and occupation.Leisure activity was obtained as a mediator by self-assessment questionnaire survey.Cox proportional hazard regression analyses were adopted to evaluate the impact of SES at different stages of life on the occurrence of cognitive impairment,and further stratified analyses were performed according to gender and age.We used the Baron and Kenny’s causal steps method to examine the relationships between baseline SES(independent variable),baseline leisure activity engagement(mediator variable)as well as subsequent cognitive impairment(dependent variable).And further,the mediating effects were assessed by using the Karlson/Holm/Breen(KHB)method.Sensitivity analysis excluding respondents with cognitive impairment at the first stage of follow-up(2008)and using subsequent leisure activities engagement as the mediating variable(2011)to repeat the above analyses.All models were adjusted for the potential confounders: age,sex,ethnic group,marital status,current smoking status,current drinking status,disability,hypertension,diabetes,and cancer.Reults: A total of 6,289 respondents aged 65 or over were included in this study,with a mean age of 79.82 ±10.22 years,of which 52.84% were female.Over a mean follow-up period of 6.42 years,cognitive impairment developed in 1,818(28.91%)participants.Cox proportional hazard regression analyses revealed that SES at different stages of life were related to the occurrence of cognitive impairment.Specifically,a one-point increment in the childhood SES score was associated with a reduction of 6.1% in the risk of cognitive impairment and a one-point increment in the adult SES score was associated with a reduction of 7.5% in the risk of cognitive impairment.In the subgroup analysis,the negative and significant associations between childhood SES(HR=0.928,95% CI:0.872～0.987,P=0.017)and adult SES(HR=0.867,95% CI: 0.794～0.947,P=0.002)and cognitive impairment were observed in females,but not in males.Childhood SES was inversely associated with cognitive impairment in the age group ≥86 years(HR=0.925,95% CI: 0.865～0.988,P=0.021),but not observed in other age groups.The Baron and Kenny’s causal steps method and KHB model presented that the mediating effects of leisure activities between childhood SES and adult SES and cognitive impairment were0.978(95% CI: 0.965～0.990,P=0.001)and 0.954(95% CI: 0.928～0.981,P=0.001),respectively.Sensitivity analysis suggested that the results of our study were relatively stable.Conclusions: We found that(1)better childhood SES might reduce the risk of cognitive impairment;(2)better adult SES might reduce the risk of cognitive impairment;(3)leisure activities partially mediated associations between childhood SES and adult SES and cognitive impairment.Our findings suggest that public health interventions aimed at preventing cognitive impairment may benefit greatly via focusing on increasing leisure activities in the elderly. |
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