Science suggests that what’s good for your body is also good for your mind: Exercise, a balanced diet, and maintaining a healthy weight all seem to be good for the brain, and may even reduce buildup of proteins related to Alzheimer’s disease.
But there are lots of other factors that can affect your risk of dementia or age-related memory loss. Some are obvious (like genetics). Others are less so. Here are a few that might surprise you.
Older women who live in areas with high levels of pollution (specifically fine particulate matter, which consists of extremely small particles that can be inhaled deep in the lungs) are 92% more likely to develop dementia than women living in cleaner-air climates, according to a 2017 study. The link was strongest in women who had the APOE4 gene, a genetic variation that increases the risk for Alzheimer’s disease. If these results hold true in the general population, the study authors say, air pollution could be responsible for about 21% of dementia cases.
“When we breathe in these tiny particles, it can trigger inflammation throughout the body,” says Richard Isaacson, MD, director of the Alzheimer’s Prevention Clinic at New York-Presbyterian Weill Cornell Medical Center (who was not involved in the study). “And for certain people, inflammation seems to be a way of pressing the fast-forward button on the progression of Alzheimer’s disease.”
You know that missing out on a good night’s sleep can lead to brain fog the next day, but research also suggests that disturbed sleep over time may be linked to a buildup of Alzheimer's-related brain proteins.
Scientists believe that exercise loosens up amyloid proteins in the brain that have been linked to Alzheimer's disease, but that good quality sleep is required to actually dispose of them, says Dr. Isaacson. “Sleep is absolutely essential for taking out the garbage and keeping your brain healthy over time,” he says.
Poor sense of smell
How well a person can recognize familiar odors may soon be an important clue to predicting the development of dementia. A 2016 study published in Annals of Neurology found that volunteers who had more trouble identifying scents like menthol, clove, strawberry, and lemon seemed to be at an increased risk of Alzheimer’s disease.
“When someone can’t distinguish between different smells, it may absolutely be a signal that Alzheimer’s disease is brewing,” says Dr. Isaacson. (It can also be a sign of Parkinson’s disease and other neurological problems, he adds.) Experts say a scratch-and-sniff test could be an inexpensive, noninvasive way to pinpoint people who might benefit from early treatment or prevention strategies.
Your eating pattern
When Dr. Isaacson’s patients ask what they can do to reduce their risk of dementia, he recommends eating an early dinner—and then nothing until breakfast the next morning. “Fasting for a minimum of 12 hours, as well as eating fewer calories overall, may be a way to promote brain health as we age,” he says.
Restricting your eating overnight can trigger the body to burn ketone bodies—a type of brain-healthy fat—rather than carbohydrates, he explains. “It helps you fuel the brain with something that’s not only more efficient from an energy-burning standpoint, but that may have an anti-aging effect as well.”
For people with a family history of Alzheimer’s, a blow to the head might accelerate the cognitive and brain changes associated with the disease. In a recent study in the journal Brain, young to middle-aged adults who’d had at least one concussion and had genetic risk factors for Alzheimer’s had less gray matter in parts of the brain associated with dementia, compared to other study participants.
Those same participants also performed worse on a simple recall test, suggesting that these brain changes could have real consequences on memory functioning. Researchers hope they may be able to use these findings to identify people at risk for Alzheimer’s disease at an earlier age.
Research shows that older adults who report feeling socially isolated may be at higher risk for Alzheimer’s disease. In a 2016 study from JAMA Psychiatry, senior citizens whose brain scans showed the development of amyloid protein clusters were 7.5 times more likely to be classified as lonely than those whose scans were negative.
Experts aren’t sure which comes first—if dementia symptoms cause people to feel left out or withdraw from social activities, or if feeling lonely actually promotes the development of dementia—but they suspect the relationship may go both ways.
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High blood pressure
You know that high blood pressure is bad for your body and your brain, so the results of a recent study published in Alzheimer's & Dementia may catch you off-guard: When hypertension develops in old age, it appears to actually reduce the risk of Alzheimer’s disease. “As we get more frail, having a reserve of blood pressure may actually be protective,” Dr. Isaacson explains.
That doesn’t mean you shouldn’t worry about high blood pressure earlier in life, though. The research is clear that for young and middle-aged adults, untreated hypertension appears to increase the risk of developing dementia later in life. "Knowing your numbers when it comes to blood pressure, cholesterol, and body mass index—and talking with your doctor about how you can optimize those numbers—is still one of the most important things you can do," says Dr. Isaacson.