Visual impairment is associated with cognitive impairment among adults aged 50 years and older in China: data from the China Health and Retirement Longitudinal Study

Abstract

BackgroundCognitive impairment is highly prevalent among older people (aged 60 years and older), and vision impairment (VI) may be a risk factor. Our study aimed to examine the relationship between VI and cognitive function among older people in China. MethodsData for 2011–2015 were drawn from the China Health and Retirement Longitudinal Study (CHARLS). Based on a national representative sample of Chinese adults aged 45 years or above, 7269 participants aged 50 years and older, who completed cognitive measurements in two or more rounds of the CHARLS survey, were included in this study. VI was assessed by two self-reported questions, about distance visual acuity for seeing faces on the other side of the street, and about near visual acuity for reading newspapers. For this study, individuals were assigned to one of four categories: no VI, distance vision impairment (DVI), near vision impairment (NVI), or both distance and near vision impairment (DNVI). Cognitive function—including episodic memory (measured as the average of immediate and delayed recall scores of ten Chinese nouns), mental intactness (measured using some components of the Telephone Interview of Cognitive Status (TICS) battery), and global cognition (the sum of episodic memory and mental intactness scores)—was evaluated and followed up every 2 years, with a mean study length of 3·17 years. We used Generalized Estimating Equations (GEEs) to estimate the association between VI and cognitive scores. FindingsThe mean age of the 7269 participants was 60·2 years (SD 7·4), and 3182 (43·77%) were women. Of the participants, 778 (10·70%) had DVI only, 1025 (14·10%) had NVI only, and 600 (8·25%) had DNVI. Compared with older people with no VI, (1) those with DVI only were associated with poor episodic memory (β=−0·076, p<0·0001), mental intactness (β=−0·074, p<0·0001) and global cognition (β=−0·089, p<0·0001); (2) those with NVI only were associated with poor mental intactness (β=−0·031, p=0·0001) and global cognition (β=−0·032, p=0·0224), but not significantly associated with poor episodic memory (β=−0·016, p=0·1639); and (3) those with DNVI were associated with poor episodic memory (β=−0·106, p<0·0001), mental intactness (β=−0·107, p<0·0001), and global cognition (β=−0·105, p<0·0001). InterpretationIn older people in China, VI is associated with an increased risk of poor cognitive function. Although the visual function was self-reported, the longitudinal findings have important implications for cognition screening and for the future design of integrated services to meet the complex needs of patients with VI—eg, embedding cognition screening within eye-care services. FundingThis work was supported by the National Natural Science Foundation of China (number 81703304).