Migraine history 'significant risk factor' for dementia, researchers from U Manitoba, U of Waterloo say

A history of suffering from migraines is a "significant risk factor" for developing different forms of dementia such as Alzheimer's disease, according to a recently published study by researchers from the University of Waterloo and the University of Manitoba — although the reason for the possible correlation remains unclear.

"[The study] helps move us along and is worth further exploration," said the University of Waterloo's Suzanne Tyas, one of the study's lead researchers. 

"It would be worthwhile and valuable to look further to find out what are the specific characteristics of migraines that are putting people at risk."

The findings of the study, published earlier this month in the International Journal of Geriatric Psychiatry, come from the Manitoba Study of Health and Aging, which analyzed 679 Manitobans, aged 65 or older, who were cognitively intact and had complete records of their migraine history.

The sample was studied over a five-year period to see who developed one of two dementia subtypes: Alzheimer's disease (the most common form of dementia) and vascular dementia, which is caused by an impaired supply of blood to the brain.

"Migraines were a significant risk factor" for Alzheimer's, the study says.

Of the 679 people involved in the study, only 34 developed Alzheimer's and 12 developed vascular dementia.

However, nearly a quarter of people who developed Alzheimer's had a history of suffering from migraines, while 17 per cent of those who developed vascular dementia had a history of migraines, the study found.

The correlation was only found in women, though — none of the men in the study who reported having a history of migraines developed dementia.

Tyas said women, generally, are more prone to suffering migraines and often live longer than men, and so are more likely to develop dementia.

The study also found that people with a history of migraines were twice as likely to develop dementia. But the researchers found that when other risk factors — such as old age, lower education, and vascular issues such as strokes — were factored in, the odds of developing dementia were three times higher, and people became four times more likely to develop Alzheimer's.

Reasons for correlation unclear

But the study doesn't come to any conclusions about why the reasons for the correlations it found.

Tyas said part of that is because it was not a biological study, but rather a population-based study to identify a trend.

Tyas said the team initially thought the link between migraines and dementia would involve the vascular system — the bodily system in charge of transporting blood — which is why the team studied things such as high blood pressure and stroke.

"We did not see this association," she said.

Tyas explained that if migraines were the result of vascular issues, then migraine history would not have an independent effect in developing dementia. But the study suggests migraine history does have an effect on its own.

"This is important because… it suggests that migraines are not impacting the risk of dementia and Alzheimer's disease by affecting the vascular system, but instead may act through other types of neurological damage." 

More study needed to confirm association

John Breitner, a professor of psychiatry and founding director of the Centre for Studies on Prevention of Alzheimer's Disease at McGill University in Montreal, commended the team behind the study for investigating the link between migraines and dementia, and encourages them to continue digging.

However, he wants to assure the public that having migraines does not guarantee dementia — it was an observation.

"To find [migraines] associated to Alzheimer's disease is certainly not impossible, but to be more sure of it, you'd certainly have to repeat it with a couple of other samples," he said.

According to Breitner, 70 per cent of dementia cases are genetic, while the other 30 per cent of cases are caused by different environmental factors.

He also notes that any injury to the head, especially any that result in unconsciousness, can accelerate the development of dementia, and the findings from the U of M and U of Waterloo study are significant.

"A doubling of risk is equivalent to experiencing the onset about five years earlier, so that is a consequence of some concern," Breitner said.

"But the fact of the matter is, the disease is so common that you can't think of it in terms of, 'Well, I've had this exposure so therefore I'm going to get the disease,' or 'I haven't, so I'm not.'"

Ultimately, Breitner said when someone will develop dementia is more important to ask than whether or not a person will develop the disease.

"[If] people live long enough, most people are going to get it," he said. "Not everybody, but most."

Both Tyas and Breitner said that because Canada has an aging population, dementia could become a larger health care issue in the coming years.

Trying to get ahead

Last June, the federal government joined many other countries, including the United States and the United Kingdom, by launching a national plan for battling dementia, which will try to get ahead of the possible burden dementia will have in the future.

Breitner says this is the right move by governments, and it's a sign that they are finally recognizing how significant a problem dementia could become within the next decade.

"It's a little late in the day, but at least Canada and a lot of other countries are definitely on the right track to be investing in this," he said. "We just hope people like me can come up with something in the next five to 10 years, that will make a big difference and reduce the morbidity of the disease."

The federal government made a commitment of $50 million dollars over a five-year period to the dementia strategy, which will be used to better prevent dementia, improve the quality of life of people living with dementia and their caregivers, advance therapies and find a cure.

Tyas explains that treatments currently available can stave off certain aspects of dementia.

"What we don't have — which is really the Holy Grail — is to find a treatment that affects the underlying disease process," she said.

Breitner isn't optimistic that medicine will ever develop a cure-all for dementia.

"The usual way we think about cure is, the patient comes to the doctor and has the symptoms. The doctor says, 'You have X, Y, Z. I need to give you this pill, or I need to do this operation.'

"So if you're talking about actually reversing the conditions, the problem there is that by the time people have symptoms, the amount of damage to the brain is so extraordinary that … it would be a very tall order indeed to reverse that."

For those reasons, both Tyas and Breitner say prevention of dementia is key, especially in mid-life — when the disease starts percolating without showing symptoms.

"Identifying factors that put people at risk of developing Alzheimer's, then helps us to target strategies that could help prevent it," Tyas said.

"Migraines is a mid-life risk factor … and it's important because we can detect earlier those people that might be at increased risk of developing Alzheimer's disease down the road."

Breitner, whose work mainly revolves around prevention, says protection from head injury, along with fitness and a heart-healthy diet, go a long way in preventing dementia.

"Anything that's good for the heart is basically good for the brain," he said, adding that keeping low blood pressure in mid-life is important too.

Ultimately, Breitner said researchers are still trying to learn more about the disease.

"We can analyze plaques and tangles in the brain with people who have Alzheimer's disease, so most of the work is concentrated on those for possible causes and actual mechanisms," Breitner said.

"So there's a lot more to learn than we already know."