[Case-control study on the influencing factors related to cognitive impairment in the elderly population of China]

Objective: To explore the influencing factors affecting the cognitive impairment of the elderly population in China. Methods: A stratified multi-stage cluster sampling was used in 6 provinces (autonomous administrative regions and municipalities) to select the sample. A total 24 000 urban and rural residents aged 60 years and above received a set of standardized questionnaire interview, physical examinations, laboratory test of lipid and glucose levels of blood and apolipoprotein E (APOE) genotype. The primary screening of cognitive function was assessed by using the Chinese Version of Ascertain Dementia 8, and then suspicious cognitive impairment cases with more than two abnormal results would receive the further cognitive function assessment by using the Mini-Mental State Examination (MMSE). 1 300 cases with cognitive impairment and 2 600 controls without cognitive impairment were recruited and matched according to their age, gender and resident area in a 1∶2 case-control study. The conditional logistic regression model was used to analyze the association between relevant factors and cognitive impairment. Results: Factors negatively associated with cognitive impairment and their OR (95%CI) values were primary or middle school as 0.63 (0.51-0.77), high school and above as 0.59 (0.39-0.88), daily neighborhood communication as 0.61 (0.50-0.75), weekly participating in social activities 0.59 (0.44-0.79), daily tea drinking as 0.71 (0.58-0.88) and doing regular exercise as 0.71 (0.57-0.88), reading newspaper (occasional: 0.50 (0.37-0.67); frequent: 0.40 (0.28-0.57)), playing majiang or cards (occasional: 0.51 (0.34-0.74); frequent: 0.50 (0.36-0.68)) respectively. Factors positively associated with cognitive impairment and their OR (95%CI) values were APOE-ε4 heterozygote as 1.31 (1.08-1.58), homozygote as 2.74 (1.52-5.00), diabetes onset before 50 years of age and after as 9.03 (3.07-33.60) and 4.40 (3.18-6.17), stroke as 1.90 (1.35-2.69), asthma as 1.95 (1.11-3.42) respectively. Conclusion: APOE-ε4 alleles, lower educational level, stroke, asthma, diabetes are risk factors of cognitive impairment in the elderly. Keeping a healthy lifestyle and preventing chronic diseases in the whole life course could significantly reduce the incidence of cognitive impairment in the elderly.