Near-Vision Loss Linked to Increased Dementia

VIENNA, Austria — Decreased near-vision function in older patients may increase the risk for later dementia, new research suggests.

Analyses from the population-based Three City study of more than 7700 participants older than age 65 years showed that those with moderate-to-severe near-vision loss at baseline were significantly more likely to develop dementia 12 years later than those who did not have any loss of function.

But there was no association between distance-vision loss and dementia risk.

"The main message is that clinicians need to be careful of eye vision and realize its importance for these patients," lead author, Virginie Nael, PhD student, University of Bordeaux, France, and employee of Essilor International, told Medscape Medical News.

Nael added that patients shouldn't assume that vision loss as they get older is just a normal part of aging, she said. Instead, they should seek out a clinical examination both to improve eyesight and to rule out other related conditions.

She presented the findings here at the International Conference on Alzheimer's and Parkinson's Diseases and Related Neurological Disorders (AD/PD) 2017.

Longitudinal Relationships

Nael noted that two main studies have assessed vision loss and dementia. One showed a lower dementia risk after 8 years of follow-up for patients with good or excellent self-reported vision, while the other (albeit a case-control study) showed a higher risk for Alzheimer's disease in those with near-vision problems.

"Our objective was to evaluate the longitudinal relationship between the two factors," said Nael.

The Three City study enrolled 9294 participants from Bordeaux, Montpellier, and Dijon, France, between 1999 and 2001, with a follow-up every 2 years. At baseline and at each follow-up, dementia cases were identified by using the Diagnostic and Statistical Manual of Mental Disorders, 4th edition.

For the current analysis, the investigators assessed the 7736 participants who had vision data at baseline. Of these individuals, 8.7% had mild near-vision loss, 4.2% had moderate-to-severe near-vision loss, and 5.3% had distance-vision loss.

Near vision was measured with a reading visual acuity test at a distance of 33 cm. Scores of 20/30 to 20/60 signified mild loss, and scores less than 20/60 represented moderate-to-severe loss.

Distance-vision dysfunction was measured by self-report, with patients noting any difficulties with recognizing a familiar face 4 m away.

At the 12-year follow-up, there were 882 incident cases of dementia. The group with dementia was significantly older than their healthy peers (76.9 vs 73.6 years, respectively; P < .001) and contained more women (65.2% vs 60.8%; P = .01) and more cases of hypertension (79.4% vs 76.8%; P < .001).

The patients with dementia included the following:

17.1% of those with mild near-vision loss;
21.2% of those with moderate/severe vision loss;
18.6% of those with distance-vision loss; and
10.2% of those with no vision loss.

In both the model adjusted for age, sex, and education and the fully adjusted model (which also included income, depressive symptoms, hypertension, smoking status, history of cardiovascular disease, and apolipoprotein E Ɛ4 genotype), moderate-to-severe near-vision loss had a significantly greater hazard ratio (HR) for dementia compared with no vision loss — but distance and mild near-vision loss did not.

Table. Association Between Vision Loss and Dementia at 12 Years vs No Vision Loss

Type of Vision Loss	Partially Adjusted Model HR (95% Confidence Interval)	P Value	Fully Adjusted Model HR (95% Confidence Interval)	P Value
Moderate/severe near	1.61 (1.23 - 2.11)	.0005	1.52 (1.15 - 2.02)	.003
Mild near	1.17 (0.95 - 1.44)	.15	1.14 (0.92 - 1.42)	.24
Distance	1.26 (0.98 - 1.62)	.08	1.04 (0.80 - 1.36)	.76

Nael noted that the distance finding could have been affected by its self-report measurement because "sometimes people don't tell the full truth," and it needs to be replicated in other longitudinal studies with validated acuity tests.

"Moreover, interventional studies are needed to confirm that improvement of visual loss may prevent or delay cognitive decline and onset of dementia," write the investigators. Still, the current results "represent a promising possibility of dementia prevention."

Which Comes First?

After the presentation, session co-chair Huaxi Xu, PhD, professor and director of the Neuroscience Initiative at the Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, told Medscape Medical News that although the findings didn't show a huge increase in risk for dementia, "it was still clearly an increase."

"The question now is: What causes what? Do vision problems cause Alzheimer's or could it be the other way around?" asked Dr Xu, noting that this area will be interesting to research further.

He also pointed out the limitation with the self-report for far distance-vision loss. "There are many things that can cause near-sightedness, including muscle [abnormality]. That could be the consequence of presymptomatic Alzheimer's change."

But if vision problems can lead to Alzheimer's, "that could be quite interesting, especially if it can help predict the disease. Or, again, it could be the other way around. There are possibilities with both cases," said Dr Xu, who was not involved with this research.

The current project received funding from the European Union's Horizon 2020 research and innovation program. Virginie Nael reported being an employee of Essilor International, which was a funder of the original study. Dr Xu has disclosed no relevant financial relationships.

International Conference on Alzheimer's and Parkinson's Diseases and Related Neurological Disorders (AD/PD) 2017. Poster 196 and Symposium 26, Presentation #3. Presented March 30, 2017.

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