Vision Impairment Linked to 19 Percent of Dementia Cases in Older Adults, Study Reveals

The findings, published in JAMA Ophthalmology, underscore the importance of using multiple measures to evaluate the relationship between vision and dementia.

Vision impairment represents a potentially modifiable risk factor for dementia. While some studies have explored the link between vision impairments and dementia, few have assessed the impact of multiple objectively measured vision deficits—such as distance and near visual acuity and contrast sensitivity—in a nationally representative sample of older adults.

Against the above background, Jason R. Smith, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, and colleagues sought to quantify the population-attributable fractions of dementia linked to objective vision impairments in older adults, with stratification by age, self-reported sex, race and ethnicity, and educational attainment.

This population-based cross-sectional analysis, part of the National Health and Aging Trends Study, examined a nationally representative sample of Medicare beneficiaries aged 65 and older in the US. The study included 2,767 community-dwelling adults eligible for vision and cognitive testing in 2021, with data analyzed between April and August 2023.

Vision impairments were evaluated using near and distance visual acuity, defined as >0.30 logMAR, and contrast sensitivity, defined as <1.55 logCS. At least one vision impairment was identified if there was a deficit in near acuity, distance acuity, or contrast sensitivity.

The main outcomes measured were the adjusted population-attributable fractions of prevalent dementia. Dementia was defined using a standardized diagnostic approach, which included being ≥1.5 standard deviations below the mean on one or more cognitive domains, a self- or proxy-reported dementia diagnosis, or a probable dementia score on the Ascertain Dementia-8 Dementia Screening Interview.

The following were the key findings of the study:

• The survey-weighted prevalence of vision impairment among participants aged 71 and older (54.7% female and 45.3% male; 8.0% non-Hispanic Black, 81.7% Hispanic, 81.7% non-Hispanic White, and 3.3% non-Hispanic other) was 32.2%.
• The population-attributable fraction of prevalent dementia from at least one vision impairment was 19.0%.
• Contrast sensitivity impairment yielded the strongest attributable fraction among all impairments (15.0%), followed by near acuity (9.7%) and distance acuity (4.9%).
• Population-attributable fractions from at least one impairment were highest among participants aged 71 to 79 years (24.3%), female (26.8%), and non-Hispanic White (22.3%) subpopulations, with estimates consistent across educational strata.

The study showed that the population-attributable fraction of dementia associated with vision impairments ranged from 4.9% to 19.0%.

"Although these findings do not establish a direct cause-and-effect relationship, they highlight the importance of incorporating multiple objective measures of vision impairments—such as contrast sensitivity and visual acuity—to fully understand the potential impact of addressing vision issues on dementia risk," the researchers concluded.

Reference:

Smith JR, Huang AR, Zhou Y, et al. Vision Impairment and the Population Attributable Fraction of Dementia in Older Adults. JAMA Ophthalmol. Published online September 05, 2024. doi:10.1001/jamaophthalmol.2024.3131