Objectively Measured Visual Impairment Associated with Higher Prevalence of Dementia

Joshua R. Ehrlich, MD, MPH

Credit: University of Michigan

Objectively measured visual impairment was associated with a higher dementia prevalence, while the presence of multiple visual impairments showed a stronger association with dementia than a single impairment, according to new research.¹

Based on objective assessments of visual function included in the 2021 National Health and Aging Trends Study (NHATS), the survey showed distance acuity, near acuity, and contrast sensitivity impairment were each associated with a higher prevalence of dementia among adults in the United States.

“The present study expands on prior work by investigating the association between objectively measured visual impairment and dementia in a contemporary, nationally representative sample and by presenting data on the association between contrast sensitivity and dementia,” wrote the investigative team, led by Joshua R. Ehrlich, MD, MPH, from the department of ophthalmology and visual sciences at the University of Michigan.

The optimization of vision is theorized to prevent up to 100,000 prevalent cases of dementia in the United States.² However, investigators note there are no contemporary nationally representative estimates of the association between objectively measured visual function and dementia. Prior estimates are based on data ≥15 years old and could be underestimating the current prevalence of visual impairment.

For the current analysis, Ehrlich and colleagues used newly available data from NHATS to estimate the cross-sectional association of objectively measured visual impairment and dementia in a nationally representative sample of adults ≥71 years. Data were included from round 11 (2021) of NHATS and analyzed from January - March 2023. In 2021, the NHATS utilized tablet-based tests of distance and near visual acuity and contrast sensitivity with habitual correction.

Visual impairments were defined as distance visual acuity ≥0.30 logMAR, near visual acuity ≥0.30 logMAR, and contrast sensitivity ≥1 SD below the sample mean. In addition, dementia was defined as a score ≥1.5 SDs below the mean in 1 or more cognitive domains, an AD8 Dementia Screening Interview Score indicating probable dementia, or diagnosed dementia. Investigators used Poisson regression to estimate dementia prevalence ratios adjusting for covariates.

The analysis identified 3817 respondents in the 2021 NHATS sample. After exclusions, there were 2967 respondents included in the analysis. Of these participants, 1707 (weighted percentage, 55.3%) were female and the median age was 76.9 years.

Upon analysis, the weighted prevalence of dementia was 12.3% (95% CI, 10.9 - 13.7) and was found to increase with near visual impairment (21.5%; 95% CI, 17.7 - 25.3), distance impairment (mild: 19.1%; 95% CI, 13.0 - 25.2]; moderate, severe, or blind: 32.9%; 95% CI, 24.1 - 41.8) and contrast sensitivity impairment (25.9%; 95% CI, 20.5 - 31.3).

The prevalence of dementia, adjusted for covariates, was higher among individuals with near visual impairment and contrast sensitivity impairment than those without (near visual impairment prevalence ratio, 1.40; 95% CI, 1.16 - 1.69; contrast sensitivity impairment prevalence ratio, 1.31; 95% CI, 1.04 - 1.66). Among those with moderate to severe distance visual impairment or blindness, the adjusted prevalence was additionally higher (prevalence ratio, 1.72; 95% CI, 1.26 - 2.35).

Analyses also showed participants with multiple visual impairments experienced a higher dementia prevalence, compared with those with a single type of visual impairment (prevalence ratio, 1.35; 95% CI, 1.03 - 1.76).The investigative team thus suggested the prioritization of vision health could be key to optimizing both sight and overall health and well-being.

“Randomized trials are warranted to determine whether optimizing vision is a viable strategy to slow cognitive decline and reduce dementia risk,” investigators wrote.

References

1. Killeen OJ, Zhou Y, Ehrlich JR. Objectively Measured Visual Impairment and Dementia Prevalence in Older Adults in the US. JAMA Ophthalmol. Published online July 13, 2023. doi:10.1001/jamaophthalmol.2023.2854
2. Ehrlich JR, Goldstein J, Swenor BK, Whitson H, Langa KM, Veliz P. Addition of vision impairment to a life-course model of potentially modifiable dementia risk factors in the US. JAMA Neurol. 2022;79(6):623-626. doi:10.1001/jamaneurol.2022.0723