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Untreated visual impairment in the elderly linked to dementia

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Vision problems could be linked to dementia and cognitive impairment. Yasser Chalid/Getty Images
  • A new study of studies finds a strong correlation between vision loss and dementia and cognitive impairment.
  • Further research should investigate a potential causal link.
  • Having eye exams and treating vision problems as they arise benefits people as they age.

It is common for older people with dementia to also experience deterioration in vision. A new study from the Center for Medical Informatics at Peking University in China suggests it could also work the other way around.

Researchers have documented a strong association between older adults who have vision problems and those who eventually develop dementia or cognitive impairment.

The study’s lead author, associate professor Beibei Xu, said:

“This study is among the first to assess the association between sight problems and cognitive outcomes in older adults through a comprehensive review of all available population-based studies in English. Our findings add to growing evidence that Vision discoloration is a risk factor for developing dementia.

However, the link between vision loss and dementia is unclear.

“Diagnosing and treating eye conditions can be beneficial – both to improve a person’s quality of life and also to potentially slow or stop memory loss.”
— BeiBei Xu, lead author

Dr Nathaniel Chinfrom the Division of Geriatrics and Gerontology in the University of Wisconsin Department of Medicine, which was not involved in the study, said Medical News Today:

“It’s a solid study. [It] did a good job in the methods employed for their systematic review and in their statistical approach to the large data set they collected. Although they acknowledge that the field has individual studies showing mixed and conflicting results, their overall assessment seems convincing that there is an association between visual impairment and cognitive decline.

Dr. Thomas J. Littlejohnssenior epidemiologist at Oxford Population Health in the UK and who was also not involved in the study, also found the study valuable, recounting DTM:

“This study helps clarify the existing evidence on the relationship between poor vision and cognitive problems.”

“It is important to note, added Dr Littlejohns, “that the study did not generate new results, but rather identified previously published studies and compiled them to produce an overall result using a mapping approach. meta-analysis.”

The study is published in the journal Aging and mental health.

The researchers searched for studies on vision loss and dementia published before 2020. Databases included PubMed, Web of Science, Baseand PsycINFO.

From these sources, the review authors selected 4,580 records, eliminating duplicates and irrelevant searches, ultimately identifying 16 high-quality studies encompassing 76,373 participants aged 50 and over.

The general conclusions of the studies were as follows:

  • Based on objective and subjective (self-reported) vision assessments, people with visual impairment had an approximately 60% higher risk of dementia or cognitive impairment.
  • At the start of the studies, the likelihood of having cognitive impairment was 137% higher in people with visual impairment than in those without.
  • Compared to people without vision problems, those who were visually impaired at the start of the studies had a 44% higher risk of incident (later) dementia, with a 41% higher risk of incident cognitive impairment.

“All of the included studies,” Dr. Littlejohns pointed out, “were observational and many measured vision alongside cognition. It is therefore not possible to determine whether visual impairment causes cognitive decline or if something else is responsible, such as poor health.

It was also a concern for Dr Chin, who explained:

“Studies like this may show an association but cannot confirm that one causes the other, which matters to the general public and patients. For causality to be determined, a randomized clinical trial is needed. »

The study does not attempt to identify the physiological link between visual impairment and dementia or cognitive impairment.

Dr. Chin mentioned that “in visual impairment, there are broken down cells in the eye and optic nerve, which leads to diminished or poor entry into the brain. This “impaired” input can lead to errors in perceptual processing and other later cognitive functions. »

“This is similar to another cause of sensory deprivation, or the ‘use it or lose it’ theory, that less stimulation of vision causes brain processes that depend on that vision to break down.”

“It may be that a reduced ability to see everyday life leads to less cognitive stimulation, or that people become more socially isolated, although this is speculation.”
— Dr. Thomas J. Littlejohns

Dr Chin noted that the apparent link could be that “people with poorer vision perform worse on cognitive tests and therefore have lower scores indicating decline or impairment when in truth the changes in the tests are related to testing for poor vision”.

Finally, Dr. Littlejohns mentioned another possibility:

“Alternatively, it could just be a spurious correlation, and more research is needed to really try to understand how visual impairment could lead to cognitive decline and possibly dementia.”

Either way, Dr. Chin, who is a practicing clinician with older patients, suggests that strengthening your vision is generally a good strategy, especially as you get older:

“When [my patient’s] eye specialist identifies cataracts, I start discussing cataract surgery. I mention the potential benefit of reducing the risk of future cognitive impairment, as well as safer driving and reduced risk of falling.

“LASIK surgery is a more complicated discussion because other non-surgical treatments may provide equal benefits but without the risk or cost of surgical complications,” Dr. Chin said, adding “If LASIK surgery were the only option for improving visual acuity is a reasonable discussion and consideration.”

“I want my patients to have clear vision for many reasons, and one of them is cognitive health. I encourage patients to have routine eye exams.
— Dr. Nathaniel Chin