Cut Your Risk Of Alzheimer's? Growing Evidence Says Maybe You Can — Modestly

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It was the "two-thirds" in the press release headline that grabbed me: "Nine risk factors may contribute to two thirds of Alzheimer’s cases worldwide."

So of course I read more about the new study:

Nine potentially modifiable risk factors may contribute to up to two thirds of Alzheimer’s disease cases worldwide, suggests an analysis of the available evidence, published online in the Journal of Neurology Neurosurgery & Psychiatry.

The analysis indicates the complexity of Alzheimer’s disease development and just how varied the risk factors for it are. But the researchers suggest that preventive strategies, targeting diet, drugs, body chemistry, mental health, pre-existing disease, and lifestyle may help to stave off dementia. This could be particularly important, given that, as yet, there is no cure, they say.

How I wish this meant that we can reduce our risk of Alzheimer's by two-thirds. But no matter how I mangle the statistics, it doesn't. Here's what it does suggest, according to Dr. James Hendrix, director of global science initiatives for the Alzheimer’s Association: that for up to two-thirds of people who have Alzheimer's, these modifiable risk factors may have contributed to it, and probably to when they got it.

"So," he says, "if you were going to get Alzheimer’s, because maybe you had a genetic predisposition, and you take very good care of yourself, maybe you don’t get it until you’re 85 or 95. But if you smoke or you’re overweight or don’t exercise, maybe you get Alzheimer’s at 75. That’s really what this says — these could be contributing factors to if you get Alzheimer’s or when you get Alzheimer’s. It increases your risk."

Of course, we've been hearing for years — at least since those smart Minnesota nuns got famous in 2001 — about how mental challenges like crossword puzzles could be linked to lower Alzheimer's risk. But this latest paper seems part of a broad shift based on growing evidence about a far greater array of "modifiable risk factors."

Exhibit No. 1: This summer, the Alzheimer's Association ran a campaign on "10 Ways to Love Your Brain," encouraging people to exercise, keep learning and quit smoking, among other advice. Exhibit No. 2: A round-up paper in the journal Alzheimer's & Dementia laying out the levels of evidence on which lifestyle and health changes could protect people against Alzheimer's.

The findings are relentlessly commonsensical: Many of the usual suspects that we already know are good for our health — exercise, heart-healthy diet, sleep, weight and blood pressure control — also appear to help fend off Alzheimer's.

I asked Dr. Gad Marshall — a neurologist and associate medical director of clinical trials at the Center for Alzheimer Research and Treatment at Brigham and Women's Hospital — how he'd respond to a neighbor who says, "Hey, I hear I can really move the needle on my risk of Alzheimer's!"

"The answer is yes, you can," he responded. "It’s not a huge difference, but it is a difference, and you do give yourself a better chance of reducing the risk of Alzheimer's disease and other dementias by doing what makes sense: Being physically active, eating a healthy diet. For these two elements, yes, we have good evidence, including some clinical trials.

"To a lesser degree, we have some evidence on cognitively stimulating activities or socializing," as being protective, he says, and still weaker evidence for the potential benefits of supplements like antioxidants or omega-3 fatty acids.

Preventive measures could stave off Alzheimer's disease by perhaps a couple of years, he says, and "right now, that's better than any medication we can prescribe. There's no medication approved for this purpose, for preventing Alzheimer's disease. And so it’s no guarantee but it does improve your chances."

Which factors matter most? At this point, Dr. Hendrix says, exercise has the strongest data behind it.

"We saw some of that data at our Alzheimer’s Association international conference last month," he says. "Not only have we seen it in terms of prevention and improving overall cognition as we age, but we also saw data looking at people who already had early stages of Alzheimer's disease -- and it appeared to have benefit even within that population."


One important point: No blame here. All these risk factors have turned up in broad population studies, but there's no way of knowing which factors contribute to any particular individual's Alzheimer's disease.

The question arises, if we already know that most of these healthful measures help fend off the No. 1 cause of death — heart disease — and people still resist healthy lifestyles, why would they care about data on Alzheimer's?

Dr. Hendrix says he's often asked that question, and "all I can say is, I’m a scientist and this is the data that we have and we’ve seen — and we want to get that information out. And maybe this will be enough to scare people to start making those changes."

Personally, I find Alzheimer's scarier than heart disease; at least heart disease can be treated. Dr. Marshall says that while there are studies of Alzheimer's drugs under way and more expected, the drugs are all still considered experimental. Studies are also under way — though more are needed — to tease out the effects of lifestyle factors. But those, too, take time.

For now, these recent papers can give us a snapshot of the state of the data on many possible Alzheimer's risk factors; the "two-thirds" paper notes that the previous studies it encompassed included 93 possible factors. More from the press release:

They found grade 1 level evidence in favour of a protective effect for the female hormone oestrogen, cholesterol lowering drugs (statins), drugs to lower high blood pressure, and anti-inflammatory drugs (NSAIDs).

They found the same level of evidence for folate, vitamins C and E, and coffee, all of which were associated with helping to stave off the disease.

Similarly, the pooled data indicated a strong association between high levels of homocysteine—an amino acid manufactured in the body—and depression and a significantly heightened risk of developing Alzheimer’s disease.

The evidence also strongly pointed to the complex roles of pre-existing conditions as either heightening or lowering the risk.

The factors associated with a heightened risk included frailty, carotid artery narrowing, high and low blood pressure, and type 2 diabetes (in the Asian population). Those associated with a lowered risk included a history of arthritis, heart disease, metabolic syndrome, and cancer.

Certain factors seemed to be linked to altered risk, depending on the time of life and ethnic background.

For example, high or low body mass index (BMI) in mid-life and low educational attainment were associated with increased risk, whereas high BMI in later life, exercising one’s brain, current smoking (excluding the Asian population), light to moderate drinking, and stress were associated with lowered risk.

The nine risk factors included obesity, current smoking (in the Asian population), carotid artery narrowing, type 2 diabetes (in the Asian population), low educational attainment, high levels of homocysteine, depression, high blood pressure and frailty.
This is an observational study, so no definitive conclusions can be drawn about cause and effect, but the researchers suggest that preventive strategies, targeting diet, prescription drugs, body chemistry, mental health, underlying disease, and lifestyle might help curb the number of new cases of Alzheimer’s disease.

Readers? Enough to change anything you do?


Carey Goldberg Twitter Editor, CommonHealth
Carey Goldberg is the editor of WBUR's CommonHealth section.