Can Addressing Vision Impairments Help Lower Dementia Risk?

Jason R. Smith, ScM

Credit: Johns Hopkins University

A cross-sectional study using data from the National Health and Aging Trends Study found that vision impairments, including contrast sensitivity and visual acuity, are linked to an increased risk of dementia.

At least one vision impairment, such as near and distance acuity deficits and contrast sensitivity, could be responsible for up to 19% of dementia cases, with the highest impact observed among women, non-Hispanic Whites and older individuals. These findings suggest that improving vision could help reduce dementia risk.

“Given the increasing prevalence of dementia in the United States and globally, addressing modifiable risk factors is a priority for dementia prevention strategies,” wrote Jason R. Smith, ScM, associated with the Department of Epidemiology at Johns Hopkins Bloomberg School of Public Health. “Systematic reviews and meta-analyses consistently indicate vision impairment is a robust risk factor for dementia and is hypothesized to impact dementia risk through similar mechanisms as hearing loss.”

As vision impairments affect up to 28% of people aged ≥ 70 years, the proportion of dementia diagnoses that are attributable to vision impairment could be significant. Further, more than 90% of impairments are considered to be preventable or correctable. Therefore, understanding the population attributable fraction of dementia due to vision issues could help public health and policy makers when creating primary prevention strategies.

Investigators examined vision impairment as a potentially modifiable risk factor for dementia using a nationally representative sample of 2,767 older adults (aged ≥ 65 years) living in the United States in 2021. Data were stratified by self-reported sex, self-reported race and ethnicity, age and education.

Vision impairment was characterized as near acuity or distance acuity (> .30 logMAR) or contrast sensitivity (< 1.55 logCS). Prevalent dementia was defined using a standardized algorithmic diagnosis including a self- or proxy-reported diagnosis, below mean on ≥ 1 cognitive domains and/or obtaining an Ascertain Dementia-8 Dementia Screening Interview Score of probably dementia.

The prevalence of vision impairment among subjects aged ≥ 71 years was 32.2%. Among these participants, 54.7% were female, 45.3% were male and 81.7% were non-Hispanic White.

The attributable fraction of prevalent dementia from ≥ 1 vision impairment was 19%, with contrast sensitivity impairment yielding the strongest fraction across impairments (15%). Other vision impairments included near acuity (9.7%) and distance acuity (4.9%).

The populations attributable fractions from vision impairments were the highest among patients aged 71 to 79 years (24.6%), female patients (26.8%) and non-Hispanic Whites (22.3%).

Strengths of the study included using data from a nationally representative sample of older adults with objective ocular impairments. Additionally, the sample provided data on subjects aged ≥ 90 years, which were missing from previous national studies and helped with the age-stratified analyses. As the study visits were performed in the subject’s home, this allowed for the inclusion of patients who may be otherwise excluded from such studies. However, investigators noted the cross-sectional design and relatively small sample sizes limited the study. Future research should also aim to include patients of Asian, Hispanic, Alaska Native and American Indian ethnicities. Additionally, they were unable to determine any associations between other measures of visual function and dementia. Lastly, these results may not be generalizable to older adults who are institutionalized.

“Overall, while not establishing a cause-and-effect relationship, these findings support considering vision health in dementia prevention strategies aimed at reducing modifiable risk factors,” investigators concluded.