THURSDAY, May 3, 2018 -- Older adults who like to bask in the heat of a sauna may be less likely to suffer a stroke, a new study suggests.
The study, of more than 1,600 Finnish adults, found that those who hit the sauna at least four times a week were about 60 percent less likely to suffer a stroke over the next 15 years -- versus people who had only one weekly sauna session.
Finland is the birthplace of the traditional sauna -- which involves sitting in a room filled with dry heat at temperatures that top 160 degrees Fahrenheit. Sauna bathing is ingrained in the Finnish culture, and most people do it at least weekly, according to the researchers on the new study.
So it's not clear whether the results would extend to other types of heat therapy -- from steam rooms to hot tubs -- that are more common in other countries, said lead researcher Setor Kunutsor.
But the findings do build on evidence that traditional saunas benefit people's cardiovascular health, said Kunutsor, a research fellow at the University of Bristol in England.
Past studies have found that frequent sauna users have lower rates of heart disease and dementia, compared to infrequent users. There's also evidence the sessions lower people's blood pressure, and make the blood vessels less stiff and more responsive to blood flow.
It's those effects, said Kunutsor, that might explain the lower stroke risk seen in this study.
The findings are based on 1,628 adults who were between the ages of 53 and 74 at the outset. None had a history of stroke.
Over the next 15 years, the people in the group suffered 155 strokes total. But the rate was lowest among those who'd used a sauna most often (four to seven times a week). In that group, the rate of stroke was just under 3 per 1,000 people each year. That compared with 8 per 1,000 among people who used a sauna only once a week.
Of course, there could be many differences between people who spend most days in a sauna and those who do not. Kunutsor said his team accounted for many of those differences -- including age and income, smoking and exercise habits, and stroke risk factors like high blood pressure and diabetes.
Even then, the results were similar.
Kunutsor acknowledged there could still be alternative explanations.
But, he said, "our findings are very convincing, given that the association remained very strong despite accounting for several factors that might explain the results."
So should everyone with access to a traditional Finnish sauna jump in?
No, Kunutsor said, since some people should avoid saunas, or at least use caution. That includes people who've recently had a heart attack or have unstable angina (chest pain that arises even at rest), and older people prone to low blood pressure.
As for other types of heat people use for therapy or relaxation, there is some evidence they have some benefits for heart and blood vessel function, Kunutsor said.
But, he added, "more evidence is needed."
Dr. Philip Gorelick, a spokesperson for the American Stroke Association, said the study was well done and "interesting."
But he sounded some notes of caution, too. For one, the findings do not prove sauna use, itself, can help prevent strokes. That would take a clinical trial, where people would be randomly assigned to use a sauna or not -- which would be logistically tough, noted Gorelick, who is also medical director of the Hauenstein Neuroscience Center in Grand Rapids, Mich.
He also pointed out that Finnish people regularly use saunas starting in childhood, so their bodies are conditioned to them.
An older person who is a sauna novice would need to be more cautious. The purported "relaxing" effect of the heat, Gorelick said, might have the opposite effect on someone who is not used to it.
He advised any older adults with medical conditions to talk to their doctor before using a sauna -- assuming they have access to one.
"Sauna use is, by orders of magnitude, less popular in the U.S.," Gorelick said.
The findings were published online May 2 in Neurology.
For advice on lowering stroke risk, visit the American Stroke Association.
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