People who engage in moderate to intense exercise seem to be less likely to suffer from "silent strokes," according to a new study.
Researchers at Columbia University in New York and University of Miami in Florida looked at 1,200 older Americans with no history of stroke and followed them for six years. The participants then were given magnetic resonance imaging brain scans.
The scans showed 16 percent of participants had the small brain lesions that indicate a silent stroke. People who reported engaging in moderate to intense exercise were 40 percent less likely to have those lesions than were the people who said they did not exercise at all.
Silent strokes are tiny blockages of blood vessels deep inside the brain. Most who have a silent stroke are unaware that it has occurred. This is because they rarely affect those regions of the brain that produce the traditional symptoms of stroke: change in a person's motor functions, speech, pain, sense of touch.
Silent strokes typically affect those regions of the brain involved with thinking and mood regulation. They may be responsible in whole or part for common ailments of the elderly -- such as urinary incontinence, poor balance, depression, apathy and confusion -- which usually are attributed to something else or just to getting old.
Officially, there are about 790,000 strokes a year in the United States. But these statistics count only those people who go to a doctor with symptoms and are diagnosed as having had a stroke or who are admitted to a hospital for a stroke, said Ashis Tayal, medical director of the Comprehensive Stroke Center at Allegheny General Hospital.
"When you include silent strokes, there could be as many as 2 million strokes a year in the United States," he said.
"These small infarcts, while they are silent, if they accumulate sufficiently they can lead to serious problems," said Lawrence Wechsler, chair of the neurology department at the University of Pittsburgh School of Medicine and director of the UPMC Stroke Institute. "Anything we can do to prevent those is worthwhile."
The study is important but not definitive, both doctors said.
"One of the issues about a paper like this is that it's hard to be sure of a direct cause-and-effect relationship," Dr. Wechsler said. "There could be intermediating factors. People who exercise vigorously could have other factors that reduce the likelihood of strokes."
"It's an association, by no means causal," Dr. Tayal agreed. But other studies have indicated exercise has a positive effect on the "metabolic syndrome" -- the cluster of conditions such as excess belly fat, elevated insulin levels, high blood pressure and high cholesterol -- that increases the risk of heart disease, stroke and diabetes, he said.
"If a person loses 10 percent of his body weight, all those things start to change," Dr. Tayal said. "People who exercise will have cardiovascular benefits, so they may be less prone to heart disease."
But both doctors said it is very likely exercise can significantly reduce the risk of silent stroke.
"The interesting thing here is that the protective effect was seen with more vigorous exercise than with mild exercise," Dr. Wechsler said.
Regular light exercise such as walking, dancing, bowling and golf did not appear to lower the incidence of silent stroke, the study indicated.
Light exercise is good for health and people shouldn't give it up, said one of the researchers, Joshua Willey of Columbia. But greater frequency and intensity of exercise seem to be required to reduce the risk of silent stroke, he said.
Jack Kelly: firstname.lastname@example.org or 412-263-1476.