The findings of a scientific study by Auckland University of Technology suggest New Zealand has the second highest lifetime risk of stroke among developed countries.
It found close to one in four 25-year-olds are at risk of developing a stroke in their lifetime.
Now the study's author is calling on the healthcare system to focus on stroke prevention at a much earlier age than 40.
Valery Feigin, author of the study, says the trend is worrying.
"It's worldwide, it's not only in New Zealand," he said. "Since 1990, the incidents of stroke in people 15-49 years is steadily increasing."
The study also found the lifetime risk of stroke remains stable from the age of 25-75.