Visual impairment increases the risk of dementia, especially in young males in a 12-year longitudinal follow-up study of a national cohort

Abstract

We investigated the effect of visual impairment (VI) on dementia development in a national cohort. In this 12-year nationwide population-based retrospective cohort study, national data were collected from National Health Insurance Cooperation of South Korea from 2002 to 2017, comprising 799,074 subjects selected from the dementia-free cohort representative of the Korean population. Crude hazard ratios (HRs) as well as age- and sex-adjusted HRs and confidence intervals (CIs) for the development of dementia were estimated using multivariable Cox regression models. VI significantly increased the risk of dementia with a HR of 2.726 (95% CI 2.251-3.300, p < 0.0001) after adjusting for age, sex, and interaction between age, sex, and VI. HR of interaction between VI and age for dementia was 0.539 (95% CI 0.436-0.667, p < 0.0001). In the sensitivity analysis after adjustment for age, sex, household income level, BMI and other comorbidities, VI showed higher risk for all the type of dementia (p < 0.0001). In subgroup analysis of VI, young males showed the highest risk for development of dementia with a HR of 2.687 (95% CI 2.219-3.254, p < 0.0001). VI significantly increased the risk of dementia in the study cohort, and young males with VI appeared to be the most susceptible to the development of dementia.

Figure 1

Flow chart of eligible subjects in the dementia-free cohort. VI = visual impairment. *Diagnosis of dementia was based on both International Classification of Diseases-10 diagnosis codes (F00, F01, F02, F03, G30, F05, or G31) and medication prescriptions [acetylcholinesterase inhibitors (donepezil, galantamine, rivastigmine) or NMDA receptor antagonists (memantine)].

Figure 2

Kaplan–Meier curves for cumulative probability of dementia occurrence according to VI status in (A) Entire cohort population, (B) Younger age population (< 65 years old), and (C) Older age population (≥ 65 years old). Those with VI depicted on the lower line had a higher rate of incident dementia across all age groups by log-rank tests (all p < 0.0001).

Figure 3

Forest plot for subgroup analyses based on age, sex, systemic comorbidities, BMI and household income level to examine the effect of VI on dementia. Forest plots were generated using the R forest plot package (https://cran.r-project.org/web/packages/forestplot/forestplot.pdf).