Most of us expect a few things to change after 50.
Our metabolism may slow down. Muscle becomes harder to maintain. Reading menus in dim restaurants suddenly requires more effort than it used to.
But researchers have now uncovered a much less obvious change taking place inside the brain — specifically in the hippocampus, the region critical for learning and memory.
And it appears to begin right around midlife.
Scientists discovered that some of the brain’s longtime immune defenders begin disappearing, while cells with a much more inflammatory profile start taking their place.
At the same time, another important defense system — the blood-brain barrier — begins showing signs of age-related decline.
Researchers are still determining exactly what these changes mean. But they could help explain something scientists have puzzled over for years:
Why does aging make the brain increasingly vulnerable to chronic inflammation, cognitive decline and dementia?
A changing of the guard in your memory center
Microglia are specialized immune cells that live in your brain.
Think of them as a combination cleanup crew and security patrol. They continually survey their surroundings, remove cellular debris and respond when something goes wrong.
And unlike many immune cells elsewhere in your body, microglia arrive early.
They begin developing before birth, and scientists have long believed that populations of these cells essentially maintain themselves throughout life.
But new research published in Science challenges that assumption.
Scientists from the University of California, San Diego, the New York Genome Center and the University of California, Irvine studied postmortem hippocampal tissue from 40 neurologically healthy people ranging in age from 20 to 95.
Using sophisticated techniques that allowed them to examine not only what individual cells were doing but also clues to where they originated, researchers spotted a striking transition.
From approximately age 50 to 75, the brain’s resident microglia gradually declined.
At the same time, cells displaying stronger inflammatory signals — and characteristics suggesting an origin outside the brain — increasingly appeared.
That could represent a profound change in the immune environment surrounding one of the brain regions you depend on most for memory.
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Your brain’s protective barrier changes, too
That wasn’t the only sign of aging researchers found.
Cells that help maintain the blood-brain barrier also showed age-related decline.
The blood-brain barrier acts much like a highly selective security gate between your bloodstream and brain tissue. It allows needed nutrients and other substances through while tightly regulating the entry of potentially damaging materials.
Researchers haven’t established that deterioration of this barrier causes the immune-cell transformation they observed.
Nor have they proven that the newly identified cell shift causes Alzheimer’s disease or another form of dementia.
Those are questions they’re investigating next.
But the findings provide another clue about why the aging brain may become more susceptible to inflammation and neurological disease.
As National Institute on Aging Director Dr. Richard Hodes explained, aging is the biggest risk factor for dementia, yet scientists still don’t completely understand how aging drives the disease.
This newly discovered immune shift could help fill in part of that puzzle.
And it raises an obvious question:
If your brain starts becoming more vulnerable around midlife, is there anything you can do to protect it?
Fortunately, we already know quite a bit about the factors associated with healthier brain aging.
Protect the vessels that protect your brain
One of the strongest places to start is your blood pressure.
High blood pressure during midlife — roughly your 40s through early 60s — is associated with an increased risk of cognitive decline later in life.
Even better, this isn’t supported only by observational research.
In the large SPRINT-MIND clinical trial, lowering systolic blood pressure to below 120 mmHg in adults 50 and older at increased cardiovascular risk significantly reduced their chances of developing mild cognitive impairment compared with a standard treatment target. Brain imaging also showed a slower accumulation of white matter lesions associated with dementia.
That doesn’t mean everyone should aim for a blood pressure below 120; the appropriate target depends on individual health circumstances.
But it does reinforce a powerful lesson:
What’s good for your blood vessels is often good for your brain.
Managing high blood pressure, blood sugar and cholesterol — and not smoking — can help protect both.
Move for your hippocampus
Exercise deserves special attention because the hippocampus itself appears to respond to physical activity.
A randomized controlled trial cited by the National Institute on Aging found that exercise increased the size of a brain structure important for memory and learning and improved spatial memory.
Other research has linked greater physical activity with beneficial changes in how the brain uses glucose for energy.
Exercise also helps counter several conditions associated with poorer cognitive health, including cardiovascular disease, diabetes and high blood pressure.
Federal guidelines recommend at least 150 minutes of physical activity each week. And walking counts.
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Give your brain better fuel
There isn’t one magic food proven to prevent dementia.
But eating patterns that support your cardiovascular and metabolic health may also support your brain.
The Mediterranean diet emphasizes vegetables, fruits, whole grains, legumes, fish and healthy unsaturated fats. The MIND diet combines elements of the Mediterranean and blood-pressure-lowering DASH diets.
Studies have associated these eating patterns with better cognitive outcomes, although clinical trial results have been mixed, and researchers continue to investigate exactly how much protection they offer.
In other words, don’t look for a single “brain food.”
Think instead about creating an eating pattern that supports the health of the entire system that supplies and protects your brain.
Make your brain keep working
Finally, don’t retire your brain just because you’ve retired from a job.
Research suggests that cognitively demanding activities can help maintain certain thinking abilities as we age. Learning something new, reading, writing, playing music and engaging in other mentally challenging activities all keep your brain working.
Social connection matters, too. Studies have linked greater social engagement with better cognitive health later in life.
None of these habits has been shown to prevent the specific immune-cell transformation researchers just discovered.
That’s important.
But the new findings give us another reason to take the brain-protective habits we already know about seriously — especially beginning in midlife.
You may not be able to stop the cellular changes that come with getting older.
But you can do quite a bit to influence the environment in which your brain ages.
And if that environment begins changing around 50, there’s no reason to wait until memory problems appear to start protecting it.
Sources:
Scientists discover a hidden brain shift that begins around age 50 — ScienceDaily
Epigenetic and 3D genome reprogramming during the aging of the human hippocampus — Science
Preventing Alzheimer’s Disease: What Do We Know? — National Institute on Aging
Cognitive Health and Older Adults — National Institute on Aging
Intensive blood-pressure control slowed white matter disease in adults age 75 and older — National Institute on Aging
What happens to your brain around age 50?
Researchers studying the hippocampus found that beginning around age 50, some of the brain’s resident immune cells, called microglia, gradually decline while cells with stronger inflammatory characteristics become more prominent. The researchers also found age-related changes in cells that help maintain the blood-brain barrier.
Do these brain changes cause Alzheimer’s disease?
Researchers don’t know yet. The study identified age-related immune and cellular changes in the hippocampus, but it did not establish that they cause Alzheimer’s disease or dementia. Scientists now want to determine whether this immune-cell transition contributes directly to neurodegenerative disease.
Why are microglia important for memory and brain health?
Microglia are immune cells that live in the brain and help monitor its environment, clear cellular debris and respond to damage or infection. Because the newly discovered changes were found in the hippocampus — a brain region essential for learning and memory — researchers are especially interested in what the shift could mean for cognitive aging.
Can you protect your brain from age-related changes?
No lifestyle has been proven to prevent the specific cellular changes found in this study. However, research supports managing blood pressure and other vascular risks, exercising regularly, eating a healthy dietary pattern and remaining mentally and socially active as ways to support cognitive health as you age.
Why is blood pressure especially important for brain health after 50?
High blood pressure during midlife is associated with greater cognitive decline later in life. In the SPRINT-MIND clinical trial, intensive blood pressure treatment in adults aged 50 and older reduced the risk of mild cognitive impairment and slowed some signs of small-vessel damage in the brain.
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