Association Between Cognitive Reserve And Cognitive Impairment In The Elderly Residents

ObjectiveTo investigate the association between cognitive reserve score(CRS)and cognitive impairment in the elderly community residents at baseline and the first wave follow-up,and the association between baseline CRS level and cognitive decline in the elderly.Materials and methodsA population-based cohort study was conducted among 1458 people aged 60 and older living in the Xing Long Zhuang community in Jining from June 2010 to July 2011.CRS related data such as the educational years,occupational types,personal income levels,social participation,and cognitive activities of subjects were collected at baseline.Clinical data of the subjects were also collected,including questionnaires,physical examinations,and laboratory test results.Using the Mini-mental State Examination(MMSE)to evaluate the cognitive function of the subjects.And the follow-up survey of 734 subjects which had no cognitive impairment at baseline were completed from June 2014 to May 2016.According to the baseline MMSE scores,participants were divided into normal cognitive function group(NC group)and cognitive impairment group(CI group).Baseline characteristics of demographics,chronic disease history,MMSE scores,physical activities,and CRS levels were compared between the two groups using t-test for continuous variables and chi-square test for categorical variables.Cognitive reserve scores consisted of years of education,occupational complexity,social engagement,and cognitive activities.According to the tertile level,CRS was divided into three levels:low,medium,and high.Multivariate logistic regression model was used to investigate the association of CRS levels with baseline cognitive dysfunction and new-onset cognitive impairment at follow-up,as well as the association between new-onset cognitive impairment at follow-up and baseline CRS levels.Multiple linear regression models were used to analyze the correlations between the sub-variables constituting the CRS and baseline MMSE scores.We calculated the rate of cognitive function changes according to the MMSE scores at baseline and follow-up,and the cognitive function decline was defined as the rate of cognitive function changing greater than 0.1.We used multivariate logistic regression model to investigate the association between the four sub-variables that constitute CRS and the decline of cognitive function.IBM SPSS Statistics 22.0 for Windows(Armonk,NY:IBM Corp.)was used for all analyses.Ap-value of equal to or less than 0.05(a)for a two-tailed test was considered to be statistically significant.ResultsThere were more women in the CI group.The LDL-C level and the prevalence of hypertension,stroke,and depressive symptoms in the CI group was significantly higher than that in the NC group,while the CRS total score,years of education,occupational complexity,cognitive activities,MMSE score,and physical activities of CI group were significantly lower than that in the NC group.There was no significant difference in age,BMI,HDL-C levels,prevalence of diabetes,prevalence of coronary heart disease,and social engagement between the two groups.Logistic regression analysis showed that at baseline,subjects with middle and high CRS levels had lower risk of cognitive impairment than subjects with low CRS levels(OR=0.435,OR=0.120,p<0.001),and the risk of cognitive impairment decreased significantly as the CRS score increased(p value trend<0.001).At follow-up,compared with low-grade CRS level,only high CRS level was a protective factor for new-onset cognitive impairment(OR=0.322,P=0.003).There was no significant association between the middle CRS level and the occurrence of cognitive impairment in the elderly(p =0.054).Multiple linear regression analysis showed that the four sub-variables that make up the CRS were significantly associated with the baseline MMSE scores(p<0.05).MMSE scores at baseline increased with increasing score of CRS sub-variables.Among them,the years of education had the greatest impact on the baseline MMSE score(?=0.473,p<0.001).Multivariate logistic regression analysis showed that the four CRS sub-variables were all factors for cognitive decline(p<0.05).The years of education was the strongest protective factor among them(OR=0.361,p<0.001).Conclusion(1)Cognitive reserve has an independent protective effect on the cognitive function of the elderly.(2)Baseline MMSE scores increase with the scores of sub-variables increasing in cognitive reserve.(3)High CRS level is a protective factor for new-onset cognitive impairment in the elderly.(4)The four sub-variables of CRS are all protective factors for cognitive decline in the elderly.(5)Increasing cognitive reserve may improve the cognitive function of the elderly and delay the decline of cognitive function.