By Dr. Mercola

It’s said that your eyes are the window to your soul, but they may also provide a unique window to your brain. As your vision worsens with age, so too may your cognitive abilities, according to research published in JAMA Ophthalmology. By the age of 65, 1 in 3 people have some type of eye disease that reduces vision, and in the U.S., about 70 million Americans will be 65 years or over by 2030.1

While it’s not a given that your eyesight will decline as you get older (a healthy lifestyle can keep your eyesight sharp well into old age), it’s important to understand that changes in vision may correlate with changes in your brain, either as an indirect consequence of changing your behaviors to accommodate them or due to an as-yet undiscovered biological component.

As it stands, both worsening vision and cognitive function are common among elderly people, but you have the ability to take control of your health so your eyes and your mind stay clear and functioning optimally.

Visual Impairment Is Associated With Worse Cognitive Function

Researchers from the University of Miami Miller School of Medicine followed 2,520 Americans for eight years.2 Their vision and cognitive status were tested at the start of the study and again four times throughout. Significant associations were found between the two.

For example, those who had worse vision when the study began had lower scores on tests of cognitive function. On average, the participants’ vision declined enough that they lost the ability to read one line on an eye chart, and visual impairment at a distance was found to be associated with declining cognitive function over time.3

The study authors noted, “Worsening vision in older adults may be adversely associated with future cognitive functioning. Maintaining good vision may be an important interventional strategy for mitigating age-related cognitive declines.”4 As for why worsening vision may lead to worsening brain function, it could be that poor vision makes it harder for people to engage in activities known to stimulate the brain, like knitting, crossword puzzles or socializing with others.

It’s also possible that vision changes could alter your brain at the structural level,5 although this needs to be further explored. The study adds more support to previous research also linking poor vision with poor cognition. In an analysis of two U.S. data sets comprised of nearly 3,000 people aged 60 years and older, visual dysfunction at a distance was associated with poor cognitive function.6

Losing your other senses, including your hearing, may also serve as a bellwether for cognitive decline. In a study of nearly 2,000 older adults, individuals with hearing loss had a 24 percent increased risk of cognitive impairment compared to those with normal hearing,7 and their cognitive function declined up to 40 percent faster.

In this case, a causal link is suspected, perhaps because hearing loss is known to affect neural systems, including those necessary for speech comprehension, which involves both working memory and information processing speed.8

Poor Vision May Increase Your Risk of Dementia, Including Alzheimer’s

People with poor vision have even been found to have a 63 percent greater risk of developing dementia,9 and leaving poor vision untreated appears to be particularly damaging. In research published in the American Journal of Epidemiology, those with poorer vision who did not visit an ophthalmologist had a 9.5-fold increased risk of Alzheimer’s disease and a fivefold increased risk of being cognitively impaired (without dementia).

“Untreated poor vision is associated with cognitive decline, particularly Alzheimer disease,” the researchers concluded, adding that it’s possible “ocular disturbances may be precursors — not consequences — of cognitive decline.” In addition, lending support to the importance of getting vision problems addressed by a professional, the authors of the featured study suggested simple interventions like updating your eyeglass prescription or removing cataracts could give your brain health a boost.10

As for the somewhat-surprising link between vision and Alzheimer’s, it could have to do with the buildup of amyloid beta, one of the hallmarks of Alzheimer’s disease. The subsequent formation of brain plaque leads to progressive decline in cognitive and social functioning — and research has also linked amyloid beta deposition to neurodegeneration in the retina.11

Amyloid beta has been found in retinal drusen (yellow-colored fatty protein deposits beneath the retina) and is a hallmark of age-related macular degeneration (AMD), the most common cause of blindness among the elderly.

Amyloid beta has been linked with the progression of AMD,12 whereas peripheral drusen has also been linked to a higher risk for Alzheimer’s.13 It’s even been suggested that by analyzing the presence of amyloid in the eye, one may be able to predict amyloid buildup in the brain with a fair degree of accuracy.14

Your Eyes May Be a Window to Your Brain Health

Aside from amyloid beta, other markers visible in your eyes may also offer clues to your cognitive health. Diseases that affect your blood vessels, veins and arteries have long been implicated in cognitive impairment, and it appears this may extend to the health of blood vessels in your eyes. Research using data that spanned 20 years and involved more than 12,000 people revealed that people with moderate to severe retinopathy, or damage to blood vessels in the retina, scored significantly lower on tests of cognitive function.15

Dr. Rachel Bishop of the National Eye Institute, who was not involved in the study, told CNN, “If the retinal blood vessels are unhealthy, there’s every reason to think that the brain blood vessels are unhealthy as well … The blood vessel supply is essential to all function, the function of all organs, and so if the blood vessels are unable to do their job, there’s no way that the brain can be functioning as well as a brain that has a good supply.”16

Getting your eyes checked, in fact, can reveal far more than the state of your vision. A skilled practitioner peering into your eyes, or hearing about changes to your vision, may be able to detect other diseases as well, including:17

Diabetes

Hypertension

Multiple sclerosis

Sexually transmitted disease like chlamydia, herpes, syphilis and HIV

Thyroid disease

Systemic inflammation due to lupus or other autoimmune diseases

Cancer

Antioxidants for Healthy Vision and Brain Function

If you’re experiencing changes to your vision, you should see an eye doctor or ophthalmologist to have them checked out. However, be aware that your lifestyle plays a major role in your vision (and brain) health, and that includes your diet. In particular, antioxidants including lutein, zeaxanthin and astaxanthin are your allies for keeping your vision sharp as you age. Lutein and zeaxanthin, in particular, are notable because they’re located in your eyes. According to the American Optometric Association:18

“Of the 600 carotenoids found in nature, only these two are deposited in high quantities in the retina (macula) of the eye … Many studies have shown that lutein and zeaxanthin reduce the risk of chronic eye diseases, including AMD and cataracts … Beyond reducing the risk of eye disease, separate studies have shown that lutein and zeaxanthin improve visual performance in AMD patients, cataract patients and people in good health.”

As an added benefit, those with higher levels of lutein in middle-age have been found to have more youthful neural responses than those with lower levels, which suggests a lutein-rich diet may also keep you cognitively sharp.19 Lutein and zeaxanthin are primarily found in organic pastured egg yolks and green leafy vegetables, with kale and spinach topping the list of lutein- and zeaxanthin-rich foods.

You’ll also find it in orange- and yellow-colored fruits and vegetables. Adding dark blue or purplish, almost black-colored berries like black currants and bilberries to your diet is another wise strategy, as they contain high amounts of antioxidant anthocyanins. Research suggests bilberry, in particular, may be effective for preventing cataracts and AMD.20

Astaxanthin Works Double Duty for Your Eyes and Your Brain

Astaxanthin is another notable nutrient that has emerged as the best carotenoid for eye health and the prevention of blindness. Research shows it easily crosses into the tissues of your eye and exerts its effects safely and with more potency than any of the other carotenoids, without adverse reactions.

Specifically, astaxanthin has been shown to ameliorate or prevent light-induced damage, photoreceptor cell damage, ganglion cell damage and damage to the neurons of the inner retinal layers. Astaxanthin provides protective benefits against a number of eye-related problems, including:

Age-related macular degeneration

Glaucoma

Cataracts

Inflammatory eye diseases such as iritis, keratitis, retinitis and scleritis

Cystoid macular edema

Retinal arterial occlusion

Diabetic retinopathy

Venous occlusion

Astaxanthin also helps maintain appropriate eye pressure, energy levels and visual acuity. Krill oil is a great source of astaxanthin that comes with the added benefit of omega-3 fats, which are also protective of healthy vision. People with the highest intake of animal-based omega-3 fats have a 60 percent lower risk of advanced macular degeneration compared to those who consume the least.21

For higher doses of astaxanthin, a supplement works well. If you decide to give astaxanthin a try, I recommend starting with 4 milligrams (mg) per day and working your way up to about 8 mg per day — or more if you’re suffering from chronic inflammation. Taking your astaxanthin supplement with a small amount of healthy fat, such as grass fed butter, coconut oil, MCT oil or eggs, will optimize its absorption.

As with lutein, astaxanthin works double duty, also protecting your brain. Researchers found that supplementing with astaxanthin-rich (microalgae) extract led to improvements in cognitive function in older individuals who complained of age-related forgetfulness.22 Another study found it may help prevent neurodegeneration associated with oxidative stress, as well as make a potent natural “brain food.”23

It’s even been found to reduce the accumulation of phospholipid hydroperoxidases (PLOOH)24 — compounds known to accumulate in the red blood cells of people who suffer from dementia — and scientists now believe astaxanthin could help prevent dementia, including Alzheimer’s. It’s becoming increasingly clear that your vision health and your brain health are intricately linked, and eating right is one of the best ways to protect both as you age.





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