Study: Strokes kill 7 million worldwide each year, and rates are rising

Climate change and worsening diets are sending global rates of stroke and stroke deaths skyward, a new study warns.

Almost 12 million people worldwide had a stroke in 2021, up 70% since 1990, according to a team led by Valery Feigin , of the Auckland University of Technology in New Zealand.

It's now the third leading cause of death in the world, killing more than 7.3 million people each year.

It doesn't have to be this way, since stroke is largely preventable, experts say.

"With 84% of the stroke burden linked to 23 modifiable risk factors, there are tremendous opportunities to alter the trajectory of stroke risk for the next generation," said study co-author Dr. Catherine Johnson . She's lead research scientist at the Institute for Health Metrics and Evaluation (IHME) at the University of Washington, in Seattle.

Some risk factors for stroke include air pollution (exacerbated by climate change), excess body weight, high blood pressure, smoking and physical inactivity. All of these hazards can be reduced or controlled, the researchers said.

The study was published Wednesday in The Lancet Neurology journal.

Besides the millions of deaths linked to stroke, these attacks often leave survivors seriously disabled. The number of years of healthy life lost globally to stroke rose by almost a third (32%) between 1990 and 2021, the report found.

Why the uptick in stroke? According to the new analysis, the rate of people's exposure to numerous stroke risk factors keeps rising.

"Between 1990 and 2021, the global stroke burden linked to high body mass index [BMI; up by 88%], high temperatures [up 72%], high blood sugar [up 32%], diet high in sugar-sweetened drinks [up 23%], low physical activity [up 11%], high systolic blood pressure [up 7%], and diet low in omega-6 polyunsaturated fatty acids [up 5%] increased substantially," according to a journal news release.

Higher temperatures mean worsening air pollution, another known risk factor for stroke. The impact of hot, smoggy days on stroke risk is perhaps most devastating in poorer nations, the researchers said, and may only worsen with climate change.

In fact, when it comes to the risk for hemorrhagic (bleeding) stroke , the risks posed by breathing in dirty air are now thought to be equal to that of smoking, the researchers noted.

Hemorrhagic stroke is much less common than ischemic (clot-linked) stroke, comprising about 15% of cases. But it is responsible for half of all the deaths and disability linked to stroke globally, the researchers noted.

Worsening diets are also playing a big role in stroke rates, as they boost rates of obesity, high cholesterol and high blood pressure, all big stroke risk factors.

That's happening even in poorer countries and among younger people, Johnson said.

"Stroke-related health loss disproportionately impacts many of the most disadvantaged countries in Asia and sub-Saharan Africa due to the growing burden of uncontrolled risk factors, especially poorly controlled high blood pressure, and rising levels of obesity and type 2 diabetes in young adults, as well as the lack of stroke prevention and care services in these regions," she said.

But change is possible, she added.

Because air pollution is closely linked to rising temperatures, "the importance of urgent climate actions and measures to reduce air pollution cannot be overestimated," Johnson said. "And with increasing exposure to risk factors such as high blood sugar and diet high in sugar-sweetened drinks, there is a critical need for interventions focused on obesity and metabolic syndromes [like diabetes]."

More information

There are tips on lowering your stroke risk at Harvard Health .

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