When we think of dementia, memory loss is usually the first symptom that comes to mind. However, recent research suggests that the eyes, specifically the retina, might offer early signs of this debilitating condition, potentially years before any formal diagnosis is made.

The retina, a critical part of our visual system, is a light-sensitive tissue lining the back of the eye. It plays a crucial role in converting captured images into signals that the brain interprets as vision. Scientists are now examining this area more closely to uncover its potential as an early indicator of dementia.

A study conducted in China earlier this year highlights the retina’s significant role in predicting Alzheimer’s disease, which is the most prevalent form of dementia known for its severe impact on memory. By tracking approximately 30,000 adults over a span of nearly ten years, researchers discovered that individuals with thinner retinas faced a higher likelihood of developing Alzheimer’s during the study period.

Moreover, the study revealed that thinner layers around the macula, the central region of the retina, were linked to as much as a 41 percent increased risk of an Alzheimer’s diagnosis. This finding underscores the importance of retinal health and the potential for eye examinations to serve as a window into our brain’s future well-being.

After following about 30,000 adults for nearly a decade, the team found people with a thinner retina were at a greater risk of developing Alzheimer’s disease within the study period. 

And in the same study, thinner layers covering the macula, the central part of the retina, were associated with up to a 41 percent greater risk of being diagnosed with Alzheimer’s disease. 

This recent research builds on past studies that have tied the eyes to dementia.  

A separate 2022 study showed that having a thicker layer around the macula was associated with better cognitive scores, and people with the thinnest macula saw the greatest decline in scores. And participants with a thinner macula were also more likely to be diagnosed with Alzheimer’s disease after the five-year follow-up. 

Changes in the eye’s retina could predict Alzheimer’s disease risk, recent studies show (stock image)

Experts believe the retina may predict Alzheimer’s risk because it is part of the central nervous system and is connected directly to the brain via the optic nerve. 

This makes the eye vulnerable to degeneration in the brain caused by Alzheimer’s disease, including nerve cell loss, inflammation and vascular damage. 

Retinal thinning can also be a sign of brain changes like reduced brain volume and atrophy. 

People with retinal thinning most often do not have symptoms at first, but as the condition progresses, it may lead to blurred vision, spots in vision, trouble seeing in dim light, reduced color or peripheral vision or a curtain-like shadow in the eyesight.

It’s most often caused by aging, eye conditions like myopia (nearsightedness) and chronic conditions such as high blood pressure and diabetes. 

Exact estimates vary, but experts suspect up to one in 10 Americans may have retinal thinning.  

The findings on retinal thinning come as Alzheimer’s disease strikes nearly 7million Americans, with that figure set to nearly double by 2050. 

In the recent study from China, published in the journal Frontiers in Aging Neuroscience, researchers looked at 30,000 adults who had not been diagnosed with dementia and were 55 years old on average. 

After an average follow-up time of nine years, 148 were diagnosed with Alzheimer’s while eight were struck by frontotemporal dementia (FTD), a form of the dementia that often strikes earlier and causes drastic personality changes, language difficulties and movement issues.

Participants underwent retinal optical coherence tomography (OCT) imaging, a non-invasive test which uses light waves to take images of the eye. The test is largely used in routine eye exams for adults over 40. 

The team found that for each unit of decrease in retinal thickness, the risk of developing Alzheimer’s disease increased by three percent, even after adjusting for risk factors such as age, sex, genetics and education. 

Rebecca Luna’s (pictured here) early-onset Alzheimer’s symptoms appeared in her late 40s. She would black out mid-conversation, lose her keys and leave the stove before returning to find her kitchen full of smoke

Jana Nelson was 50 when diagnosed with early onset dementia, following severe personality changes and a sharp cognitive decline that left her unable to solve simple math problems or name colors

Thinning of the macula was also associated with a 41 percent increased risk of FTD, though the team noted more research is needed because only eight participants developed FTD. 

In a separate study from South Korea, researchers looked at 430 adults with an average age of 76 who underwent OCT testing. 

After five years, the team found people with a thicker macula lining had higher cognitive scores, and there was a greater decline in scores among those with thinner macula linings.  

To prevent retinal thinning, eye experts recommend focusing on a diet filled with nutrients such as omega-3s, which prevent inflammation and other brain damage linked to dementia, and exercising regularly.