Vision impairment may be modifiable risk factor for dementia
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Key takeaways:
- Contrast sensitivity had the strongest population attributable fraction of dementia of all vision impairments.
- The attributable fraction of dementia from having at least one vision impairment was 19%.
Addressing vision impairments, including reduced contrast sensitivity and visual acuity, may have a significant effect on dementia prevalence, according to a study published in JAMA Ophthalmology.
“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” Jason R. Smith, ScM, from the department of epidemiology at Johns Hopkins University Bloomberg School of Public Health, and colleagues wrote. “Since vision impairments are common among older U.S. adults, affecting up to 28% of those older than 70 years, the proportion of dementia attributable to vision impairment might be sizable.”
Seeking to quantify population attributable fractions (PAFs) of dementia from three vision impairments — near and distance visual acuities and contrast sensitivity — Smith and colleagues conducted a population based, cross-sectional analysis in the National Health and Aging Trends Study. They identified 2,767 adults (54.7% women; 81.7% non-Hispanic white, 8% non-Hispanic Black, 7.1% Hispanic and 3.3% non-Hispanic other ) aged 71 years and older who were eligible for vision and cognitive testing in 2021.
According to results, the prevalence of at least one vision impairment was 32.2%, which was associated with older age, lower education level and identifying as non-Hispanic Black. Among those with at least one impairment, the prevalence of near acuity and contrast sensitivity impairments were 65.3% and 63.1%, respectively — twofold higher than that of distance acuity impairment at 30.1%.
The PAF of dementia from at least one vision impairment was 19%, with contrast sensitivity (15%) linked to the strongest PAF, followed by near acuity (9.7%) and distance acuity (4.9%).
While prevalence of vision impairment was associated with older age, the researchers reported that the PAFs decreased with age — from 24% at 71 to 79 years to 8% at 90 years or older. In addition, the PAFs for at least one vision impairment were higher among women vs. men (27% vs. 7%) and non-Hispanic white vs. non-Hispanic Black individuals (22% vs. 16%), with similar findings for contrast sensitivity impairment in these population subgroups (19% vs. 9% and 20% vs. 6%, respectively).
“The total contribution of late-life vision impairment to dementia may be substantial and warrants further examination to inform dementia prevention strategies,” Smith and colleagues wrote. “Furthermore, this investigation suggests that studies underestimate the impact of vision impairment on dementia if vision impairment is defined simply using distance visual acuity.”
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