In one US region, strokes under 55 nearly doubled while falling in older adults

Between 1993 and 2020, first strokes among adults aged 20 to 54 in the Cincinnati area rose from 33.9 to 62.2 per 100,000 person-years. A person-year is one person followed for one year, so this is roughly a yearly rate per 100,000 people. Over the same decades, the rate in older adults fell, from 618.8 to 453.0.

Older adults still have far more strokes. But the two trends are moving in opposite directions.

Most of the increase came from ischemic strokes, the kind caused by a blocked blood vessel, which climbed from 23.8 to 47.3 per 100,000. Younger patients were also less likely to die within a month of their stroke: 9.4% in 2020, down from 11.7%.

The researchers looked at who these patients were. High blood pressure, diabetes and atrial fibrillation (an irregular heart rhythm) all became more common among young stroke patients. Substance use jumped from 4.6% of patients to 40.2%, mostly linked to marijuana.

That last figure is easy to over-read. The study counted risk factors only in people who had a stroke, with no comparison group of people who didn't, so it can't tell which change drove the rise. The data also come from a single five-county region that may not match national trends. Which of these shifts is doing the damage remains an open question.