July 16 (Bloomberg) -- While the rate of strokes among Americans has dropped by about half since the 1980s, people younger than 65 saw less of a decline, according to scientists concerned that rising obesity could reverse the downturn.
The rate of first-time strokes in the U.S. dropped 24 percent in each of the last two decades while accompanying deaths fell 20 percent per decade, according to research published in the Journal of the American Medical Association. Less smoking and improved treatment of hypertension and high cholesterol made the difference, researchers said.
Still, nearly 800,000 Americans have a stroke yearly and 130,000 die, making it the fourth-leading cause of death, according to the Centers for Disease Control and Prevention. With obesity and diabetes on the rise, the concern is the declines won’t continue, doctors said.
“That’s a bit of an alarm bell that we need to pay more attention to,” said Ralph Sacco, chairman of neurology at the University of Miami Miller School of Medicine, by telephone. Sacco wrote an editorial addressing the findings in the journal.
Most of the drop occurred in those 65 years and older, with the number of strokes falling 31 percent per decade. That compares to a drop of about 3 percent per decade for those under 65 years, said study author Josef Coresh, a professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health in Baltimore.
However, researchers also found that most of the decline in stroke death was seen in those younger than 65 years. Among people under age 65, the risk of dying from stroke dropped by 35 percent during each decade of the study compared with 6 percent for those ages 65 years and older, Coresh said.
“We don’t know if the trend will continue,” said Coresh in a July 11 telephone interview. “It’s good that we’re doing better but we can’t let our guard down. With the obesity epidemic maturing, people who have had obesity and the subsequent risk factors for longer may reverse this trend.”
A study last year in The Lancet medical journal found that the number of people ages 20 to 64 who experience strokes has risen by 25 percent in the past two decades, according to researchers from countries including the U.S., U.K. and Japan. This younger group now makes up 31 percent of total strokes, compared with 25 percent before 1990, the study found.
Researchers in the study analyzed results from the Atherosclerosis Risk in Communities study of 15,792 residents in the U.S. who were ages 45 to 64 when the study began in the late 1980s. The analysis included 14,357 people through 2011.
They found that 1,051 people, or 7 percent had a stroke over the more than two decades. The decline in strokes was seen in both whites and blacks over this period and in both men and women. Of those who had a stroke, 614 people, or 58 percent, died through 2011.
Strokes happen when blood flow to the brain stops. Brain cells begin to die within minutes, according to the U.S. National Institutes of Health. The brain cells aren’t replaced, leading to disability.