Findings from a study published in the American Journal of Ophthalmology evaluated the impact of baseline and change in visual acuity (VA) and contrast sensitivity (CS) on the risk of developing dementia.
Give me some background.
Visual impairment (VI) is considered a leading cause of disability, affecting one in four older adults over the age of 70 years in the United States.
Similarly, dementia is strongly associated with aging and leads to limitations in functional ability.
Keep going…
Previous studies have shown links between baseline VA and CS with incident dementia and cognitive decline.
However, there is still a dearth of knowledge on how changes in VA and CS can affect incident dementia.
Consequently, a research team from Johns Hopkins University sought to elucidate the relationship between VI and dementia to develop a more nuanced understanding of the two—as well as provide insights into their temporal relationship.
Now the study.
In this retrospective cohort study, researchers performed longitudinal analyses on data from the 2021 and 2022 National Health and Aging Trends Study (NHATS).
The NHATS gathers information on a nationally representative sample of Medicare beneficiaries ages 65+, and is used by researchers to study national- and local-level disability trends.
How did they define visual function and dementia?
Binocular presenting vision was assessed, including:
- Distance visual acuity (DVA)
- Near visual acuity (NVA)
- CS
Dementia status was defined based on:
- Medical diagnosis of dementia
- Dementia score
- Poor cognitive test performance
Findings?
In total, 2,159 adults (mean age at baseline: 77.9 years; 54% female patients; 88% White) were included in the study.
The baseline median (interquartile range [IQR]) VAs were as follows:
- DVA: 0.08 (0-0.20) logMAR
- NVA: 0.17 (0.09-0.26) logMAR
- CS: 1.80 (1.65-1.85) logCS
What else?
Over the 1-year follow-up period, 192 (6.6%) of adults developed dementia.
Using time-to-event analyses, investigators found that the VAs below were associated with a greater likelihood of incident dementia:
- DVA (hazard ratio [HR]: 1.08, 95% confidence interval [CI] 1.02-1.14, per 0.1 logMAR)
- NVA (HR: 1.07, 95% CI 1.01-1.13, per 0.1 logMAR)
- CS (HR: 1.09, 95% CI 1.03-1.15, per 0.1 logCS)
The change in CS (HR: 1.14, 95% CI 1.04-1.25, per 0.1 logCS worse/year)—but not VA—was associated with a greater likelihood of incident dementia.
Expert opinion?
According to the study authors, “CS change may also be a more sensitive indicator of dementia compared to VA change, as shown with significant associations following a short follow-up duration (1 year), and interventions targeted at preserving/improving CS may alter the risk of dementia.”
Take home.
These findings suggest that worse baseline VA and CS are associated with an increased likelihood of incident dementia.
Additionally, worsening CS over time was associated with a higher likelihood of incident dementia.
And for the future?
Further studies are required to elucidate interventions targeted at improving vision deficits and examining their impact on decreasing dementia risk.