Partaking regularly in the relaxing practice of sauna bathing is associated with a decreased risk for dementia and Alzheimer's disease (AD) — at least in men, new research suggests.
Further results from the Kuopio Ischemic Heart Disease (KIHD) study, which included more than 2300 middle-aged men in Finland who were deemed healthy at baseline, showed that those whose sauna use averaged 4 to 7 times per week were 66% less likely to develop dementia at 20-year follow-up than men who used a sauna once a week. In addition, they had a 65% risk reduction for AD.
The report "provides promising results from the first prospective study that shows sauna bathing to be a potential protective lifestyle factor for common memory diseases," write the investigators, adding that the practice "may be a recommendable intervention" to prevent the condition in healthy adults.
However, they note that more studies are needed in different patient populations, including women.
Still, senior author Jari Antero Laukkanen, MD, PhD, professor at the University of Eastern Finland, Kuopio, told Medscape Medical News that he was pleased with the results.
"This study was surprising because the findings were so strong," said Dr Laukkanen. "People have positive feelings about sauna bathing," which may help in part to explain the associations found, he added.
The results were published online December 7 in Age and Ageing.
"Time Well Spent"
As reported by heartwire from Medscape, the investigators previously examined the KIHD study population to determine possible links between sauna bathing and cardiovascular events.
They found that the men who used saunas as little as two to three times per week had significantly lower rates of sudden cardiac death/fatal coronary heart disease, fatal cardiovascular disease, and all-cause mortality 18 years later compared with those who used saunas only once a week.
At the time, Rita F. Redberg, MD, University of California, San Francisco, wrote in a JAMA Internal Medicine Editor's Note that although the study didn't include mechanistic examination, "clearly time spent in the sauna is time well spent."
Dr Laukkanen noted that after looking at the associations with cardiovascular disease the researchers next wanted to turn their attention to dementia "because together, they often share comorbidities and risk factors."
The original KIHD study was created to examine risk factors for atherosclerotic cardiovascular outcomes in a randomly selected, population-based sample of men from eastern Finland.
For the current analysis, the investigators examined a cohort of 2315 of the participants who reported their sauna use. All of the men were aged 42 to 60 years at baseline (mean age, 53.1 years).
Traditional Finnish saunas were used by all of the study participants. These versions have dry air and a recommended temperature of 80 to 100°C. And humidity "is temporarily increased by throwing water on the hot rocks of [the] sauna heater."
The men were split into 3 subgroups based on weekly sauna use averages: once a week (n = 601), 2 to 3 times a week (n = 1513), and 4 to 5 time a week (n = 200).
The mean follow-up time was 20.7 years. For each group, from the least sauna use to the most, the percentages with a dementia diagnosis were 10%, 9%, and 4%, respectively; 6%, 6%, and 3% had an AD diagnosis.
After adjustment for a multitude of factors, including age, body mass index, smoking status, alcohol consumption, and having had a prior myocardial infarction, the hazard ratio (HR) for dementia was 0.34 for the 4 to 7 times per week sauna bathers vs the once a week bathers (95% confidence interval [CI], 0.16 - 0.71; P = .004).
The HR for AD for the same comparison was 0.35 (95% CI, 0.14 - 0.90; P = .03).
There were no significant associations with dementia or AD for the 2 to 3 times per week vs once per week sauna bathers.
Overall, the findings show "a strong inverse association between frequency of sauna bathing and the risk of dementia and [AD], which was independent of known risk factors," write the investigators.
They note that recent evidence has suggested that inflammation and oxidative stress may contribute to the pathogenesis of dementia.
"Our results are therefore biologically plausible as regular sauna bathing is associated with improved vascular endothelial function, which also leads to reduced inflammation," the researchers write.
"Additionally, sauna bathing may be beneficial in the reduction of high systemic blood pressure and elevated pulse pressure, which are also well-known risk factors for dementia."
Dr Laukkanen added that he thinks the results are generalizable "to other populations in the northern part of the world: in northern countries in Europe and in North America, where they have cold weather. But I don't know how generalizable it would be in warmer countries."
He reported that the researchers are planning future studies that will assess these associations in women and assess other physiologic changes with sauna use.
The study was funded by the Finnish Foundation for Cardiovascular Research. Dr Laukkanen and the other study authors have disclosed no relevant financial relationships.
Age Ageing. Published online December 7, 2016. Abstract
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Cite this: Sauna Use Linked to Lower Dementia, Alzheimer's Risk - Medscape - Dec 29, 2016.