Extreme heat from climate change increasing risk of stroke - and death

More people will suffer strokes if climate change continues to progress as its current rate, a neurologist says.

Last week, the World Health Organisation warned climate change was posing an "escalating threat" to brain health with extreme heat increasing the risk of people suffering a stroke - and dying from it.

The latest research was published in the International Journal of Stroke. Professor Anna Ranta, who works in the Department of Medicine at Wellington's University of Otago and is also a member of the World Stroke Organisation's board of directors, was one of its lead authors.

Ranta told Nine to Noon on Tuesday the risk comes from factors like extreme temperature, humidity, wildfires, and sandstorms.

While there is a known link between air pollution and strokes - with 20 percent of strokes globally linked to it - the authors wanted to see what environmental changes were likely to do to the risk of stroke as they evolve with climate change.

Ranta said "several" risk factors were identified but it was an evolving field and they were still working to understand the mechanisms.

"What is becoming clear is that what happens is often the system gets quite overwhelmed by a number of factors that are happening concurrently - so if it's very hot and humid, people get dehydrated, their blood gets thicker and they get more ... the whole system gets a bit overwhelmed and that may be a reason for why strokes can be more severe.

"When you're looking at who is impacted by this, it is often people who already are at risk of stroke and other cardiovascular diseases, elderly people, people who are exposed to multiple risk factors in the environment, people working outside, like outside workers, people in low-to-middle income countries with less resilience of infrastructure, so it's often a multi-factorial event that occurs that may be why mortality increases and why the overall risk increases."

Ranta said there was also an increased risk for people who already have less access to healthcare and good health outcomes.

Increasing weather events that disrupt infrastructure and people's ability to access healthcare was another problem.

Because of this, readiness was needed, and while prevention was always best, investment was needed to make sure people could be ready for adverse weather events, Ranta said.

She said at a government level, there needed to be a focus on policies to reduce the impacts of climate change and reduce more of it.

At a medical level, Ranta said there needed to be an increase in advocating for emission reduction to prevent the "damage that is now and that is going to get even worse".

"As far as adapting to these changes, so we need to shift a little bit or increasingly concern ourselves with how can we be ready?"

This included making sure homes were well insulated, and people who did not have that luxury could access shelter during extreme weather events.

"We need to make sure there are early warning signs so that we can warn the public when these events occur and have some predictability of it and we also need to invest in research to actually test some of these strategies."

In general, however, Ranta said staying well hydrated was an "excellent strategy" at reducing risk.

But the risk was still there.

"We do think that if climate change continues at the rate it is now, we will see a gradually increase in health effects including stroke."

Sign up for Ngā Pitopito Kōrero, a daily newsletter curated by our editors and delivered straight to your inbox every weekday.