New science is challenging the glum idea that nothing you do can lower your chances of getting Alzheimer’s disease. While key risk factors — age, race, gender — have been known for a while, and they remain part of the Alzheimer’s equation, recent research has identified other potential contributors. The good news: It is estimated that one-third to two-thirds of Alzheimer’s cases can be pinned on things that are under your control.
Here’s the latest scientific thinking on managing your risks.
Risk: your genes
About 25 percent of Americans have a copy of the Alzheimer’s gene (APOE e4), tripling their risk of getting the disease. Another 2 percent have two copies of the gene, boosting their odds eightfold to twelvefold. The APOE e4 gene creates a protein that moves cholesterol around in your body. But for some people, the APOE e4 variant has a dark side — it has been linked to the buildup of sticky amyloid plaque in the brain, leading to earlier memory failure and brain-cell loss. While the average age of an Alzheimer’s diagnosis is 84 years old for people without the APOE e4 gene, it strikes between eight and 16 years earlier for those with it. In one international study of 27,109 people with Alzheimer’s, just under half had the APOE e4 gene, and nearly 10 percent had two copies.
Fight back: Cut cholesterol. “Your genes aren’t your destiny,” says Jesse Mez, M.D., assistant professor of neurology at Boston University. “Plenty of people with the APOE e4 gene do not develop Alzheimer’s disease. A healthy lifestyle can really make a difference.” Case in point: Keeping cholesterol under control meant a lower risk for mental decline in people with the Alzheimer’s gene in a recent large German study.
Risk: your family history
Studies suggest having one parent, brother or sister with late-onset Alzheimer’s disease increases your risk twofold to fourfold. The APOE e4 gene accounts for about 50 percent of this risk; other genes may be involved, according to researchers at Duke University.
Fight back: Work together. Lifestyle habits you share with your family may also play a role in getting the disease, according to the Alzheimer’s Association. So make healthy changes together.
Risk: a head injury in your past
Moderate to severe head injuries that knock you out for 30 minutes or longer, such as from a car accident, can increase Alzheimer’s risk by 2.3 to 4.5 times. Mild head trauma doesn’t seem to raise the risk.
Fight back: Prevent falls. Do what you can to prevent hard falls. In a 2014 Mayo Clinic study of 448 older adults, brain scans revealed higher levels of amyloid plaque in people with mild memory problems who’d had a brain injury that knocked them out.
Having high blood sugar doubled the risk of Alzheimer’s in one large study that tracked 1,017 people for 15 years. Excess blood sugar harms blood vessels in the brain, while insulin resistance may set the stage for an accumulation of plaques and tangles.
Fight back: Medicate. In two studies, diabetics who took the medication pioglitazone or metformin significantly cut their risk for developing Alzheimer’s.
Research shows smokers face a 59 percent higher risk for Alzheimer’s than nonsmokers. Tobacco amps up oxidative stress in the brain, allowing cell-damaging compounds called free radicals to run wild, accelerating the buildup of plaques and tangles.
Fight back: Stop. Experts point out that arteries become healthier within six months of quitting, which could have brain benefits. Quitting cuts the risk of strokes, which make Alzheimer’s worse.
Emerging risks: microbes and gut bugs
Cutting-edge Alzheimer’s research is finding other potential causes of the disease.
Common bugs such as herpes simplex virus 1 (the virus that causes fever blisters) and Chlamydia pneumoniae (a bacteria that causes pneumonia) may also trigger late-life brain infections that destroy or inflame brain tissue and trigger the production of plaques and tangles as a defense mechanism, say researchers including Brian J. Balin, a professor of neurobiology at the Philadelphia College of Osteopathic Medicine.
Meanwhile, other researchers suspect that an unhealthy balance of gut bugs in the modern digestive system may play a role by increasing inflammation. People with Alzheimer’s had fewer types of gut bugs than those without Alzheimer’s in a recent University of Wisconsin study. Modern hygiene may be knocking out good bugs, contributing to the risk, researchers note.