A tiny leak in your blood-brain barrier may explain forgetfulness, onset of Alzheimer’s disease

SEATTLE, Wash. — You may have heard about patients suffering from a constant runny nose that turned out to be leaking brain fluid. While such injuries are rare, a new study finds there’s another leak in the brain that simply comes from age. Researchers at the University of Washington say a tiny leak in the blood-brain barrier may be the reason for general forgetfulness and a failing memory as people grow old.

The blood-brain barrier is a key component of any healthy brain. This complex system of blood vessels runs through the brain and protects against harmful substances reaching the organ. Researchers say it’s still unclear if the blood-brain barrier affects actual brain function. What their study does find is that the barrier leaks as people age and loses key cells, called pericytes.

“It turns out very little is known how the blood-brain barrier ages,” says lead author and gerontology researcher William Banks in a university release. “It’s often hard to tell normal aging from early disease.”

The blood-brain barrier’s connection to Alzheimer’s disease

Scientists discovered the blood-brain barrier in the late 1800s. This natural defensive bubble keeps out many of the substances in blood that the brain can’t tolerate. On the positive side, it also allows particles into the brain which fill the organ’s nutritional needs. Additionally, the barrier transports informational molecules from the blood into the brain, while pumping out unhealthy toxins.

Researchers say when the blood-brain barrier isn’t working properly, diseases like multiple sclerosis, diabetes, and Alzheimer’s can develop. Before scientists can figure out how a malfunctioning barrier leads to disease however, the team says they first need to know what a normally-aging blood-brain barrier looks like.

The study finds even healthy individuals have a tiny leak in their blood-brain barrier. This small drip has a link to some of the harmless forgetful moments people have, like forgetting where you parked. However, scientists fear the link between this leak and failing memory may be an early sign of Alzheimer’s.

When patients carry the ApoE4 allele gene — the strongest genetic risk for Alzheimer’s — researchers say the age-related changes in the blood-brain barrier accelerate. Patients with ApoE4 have more difficulty getting rid of amyloid beta plaque build-ups in the brain. This is one of the key symptoms of dementia, as the plaque interferes with and eventually kills brain cells.

As people age, pumps in the blood-brain barrier begin to fail and become less effective at removing amyloid beta peptides. For Alzheimer’s patients, these pumps work even less effectively.

The cells key to blood-brain barrier health

Study authors discovered that, as people age, two cells in the barrier being to change — pericytes and astrocytes.

Recent studies reveal that blood-brain barrier leaks occurring during Alzheimer’s are likely due to a loss of pericytes. Astrocytes, on the other hand, seem to be overactive as the body gets older. Scientists believe preserving pericyte function or transplanting new ones may restore the barrier to health.

Studies also reveal that regular exercise, watching your calorie intake, and the drug rapamycin may help improve pericyte health.

The study appears in the journal Nature Aging.

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