Summary: Vision impairment in those over 71 could be a potential risk factor for dementia, a new study suggests. By analyzing the National Health and Aging Trends Study (NHATS), the researchers found a notable association between sight loss and the prevalence of dementia among nearly 3,000 US participants.
While further investigation is needed to understand the exact cause of this connection, the findings potentially add sight loss to the list of modifiable risk factors for dementia.
The study involved nearly 3,000 US citizens over 71 years old and found a significant link between sight loss and the prevalence of dementia.
Currently, sight loss is not considered among the 12 established risk factors that influence up to 40% of dementia cases, such as smoking, high blood pressure, and hearing loss.
Several possibilities might explain this connection, including shared brain pathways causing both vision loss and memory decline or other conditions like diabetes that can cause both vision problems and dementia.
Source: Alzheimer’s Research UK
A new study suggests that sight loss in people over 71 years old may be linked to dementia.
The study was published on July 13 in JAMA Ophthalmology.
The researchers at the University of Michigan in the US analyzed data from nearly 3,000 US citizens over 71 years old, who were part of a larger study, the National Health and Aging Trends Study (NHATS).
This larger study tested the participants’ eyesight and recorded their scores for short-distance vision, long-distance vision and how well they were able to distinguish objects against different backgrounds. They also found out whether the participants had dementia from the NHATS study data.
What they found was that participants with sight loss were more likely to have dementia compared to people with no problems with their vision.
Up to 40% of dementia cases could be influenced by 12 risk factors which we may be able to prevent or influence, such as smoking, high blood pressure and hearing loss. Sight loss is not currently one of these 12 important risk factors, but the new evidence published today suggests that there is a link between sight loss and dementia.
Dr. Susan Mitchell, Head of Policy at Alzheimer’s Research UK, said, “This is a crucial time for dementia research, as evidence builds about how factors such as sight loss are linked to dementia. Studies like this are crucial for identifying possible new dementia risk factors and ultimately working out how to potentially prevent some cases of dementia from happening in the first place.”
“This new study provides important new evidence linking sight loss to dementia and ties in with previous studies. But this isn’t definitive, and it will be important for future studies to find out precisely what is causing this apparent link, as this will determine what, if any, potential there is for prevention.”
“There are several possibilities—for example, diabetes is a key risk factor for dementia, and this condition can also cause vision problems. Or it might be that there are shared pathways in the brain that cause both vision loss and a decline in memory and thinking abilities.
“Some cases of sight loss are preventable, and others can be treated successfully—if this link is confirmed, this could mean people who take steps to minimize sight problems as they get older could also help reduce their risk of conditions like dementia.”
“In the meantime, we can all take action to protect our brain health, from keeping our hearts healthy to enjoying new activities and social interactions.
Objectively Measured Visual Impairment and Dementia Prevalence in Older Adults in the US
Estimates of the association between visual impairment (VI) and dementia in the US population are based on self-reported survey data or measures of visual function that are at least 15 years old. Older adults are at high risk of VI and dementia so there is a need for up-to-date national estimates based on objective assessments.
To estimate the association between VI and dementia in older US adults based on objective visual and cognitive function testing.
Design, Setting, and Participants
This secondary analysis of the 2021 National Health and Aging Trends Study (NHATS), a population-based, nationally representative panel study, included 3817 respondents 71 years and older. Data were analyzed from January to March 2023.
In 2021, NHATS incorporated tablet-based tests of distance and near visual acuity and contrast sensitivity (CS) with habitual correction.
Main Outcomes and Measures
VI was defined as distance visual acuity more than 0.30 logMAR, near visual acuity more than 0.30 logMAR, and CS more than 1 SD below the sample mean. Dementia was defined as scoring 1.5 SDs or more below the mean in 1 or more cognitive domains, an AD8 Dementia Screening Interview Score indicating probable dementia, or diagnosed dementia. Poisson regression estimated dementia prevalence ratios adjusted for covariates.
Of 2967 included participants, 1707 (weighted percentage, 55.3%) were female, and the median (IQR) age was 76.9 (77-86) years. The weighted prevalence of dementia was 12.3% (95% CI, 10.9-13.7) and increased with near VI (21.5%; 95% CI, 17.7-25.3), distance VI (mild: 19.1%; 95% CI, 13.0-25.2; moderate, severe, or blind: 32.9%; 95% CI, 24.1- 41.8), and CS impairment (25.9%; 95% CI, 20.5-31.3). Dementia prevalence was higher among participants with near VI and CS impairment than those without (near VI prevalence ratio: 1.40; 95% CI, 1.16-1.69; CS impairment prevalence ratio: 1.31; 95% CI, 1.04-1.66) and among participants with moderate to severe distance VI or blindness (prevalence ratio: 1.72; 95% CI, 1.26-2.35) after adjustment for covariates.
Conclusions and Relevance
In this survey study, all types of objectively measured VI were associated with a higher dementia prevalence. As most VI is preventable, prioritizing vision health may be important for optimizing cognitive function.