Can Blood Tests Predict Dementia?

There’s promise that blood tests could someday predict dementia as much as a decade before the disease strikes. Early detection could lead to effective prevention.

More than one blood test has emerged promising to catch signs of Alzheimer’s disease, the most common form of dementia, before symptoms appear. Early detection, researchers hope, could lead to prevention.

One test, based on fats in the bloodstream, may catch the signs within three years of onset, with 90 percent accuracy. Another looks at blood proteins and catches onset up to a year of advance with similar accuracy.

To push detection earlier, researchers have focused on one protein, IRS-1, important in how the brain monitors insulin. One form of it is inactive and another form is active. In research, participants who had more of the inactive and less of the active form of IRS-1 eventually developed Alzheimer’s.

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Researchers looked at frozen blood samples taken up to 10 years before an Alzheimer’s diagnosis. Based on clues from IRS-1, researchers could tell in every case which samples came from someone with Alzheimer’s.

You’ll recognize insulin as the hormone people with diabetes take to manage their blood sugar. The connection between insulin and Alzheimer’s has led some scientists to think of it as type 3 diabetes, or diabetes of the brain, in which chronic insulin resistance leads to a shortage of insulin in the brain. In type 1 diabetes, your body produces no insulin at all. In type 2 diabetes, the pancreas does produce insulin but not enough, or your body has developed a resistance to insulin so it needs more than the usual amount.

Another blood test promises to show when a patient already has Alzheimer’s, so it could be used to confirm a diagnosis based on early symptoms

These tests are not completely established or available commercially, but the company that developed the IRS-1 test won its first patent in 2018.

The hope is that tests would help doctors instruct patients how they can delay the disease. In fact, they may benefit from drugs already in use to treat or push off insulin resistance.

In the meantime, you’re not alone if you worry that memory lapses will turn into disabling dementia. Your best move is to do everything you can to be healthy. In one randomized controlled clinical trial, the gold standard of research, older adults had less mental decline over two years if they ate healthily, exercised regularly, and took part in social events.

It’s also a good idea to keep learning new things — for instance, a new language. But look for real-life learning opportunities. Computer- or video-based exercises can sharpen your attention and ability to respond quickly — but you might simply get better at the game. Your goal should be to improve your attention and response times when you’re active — for instance, when working, driving, playing sports, or minding children and elders.

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