Frequent sauna bathing is associated with a more than 60% reduced risk of stroke, according to a 15-year follow-up Finnish study.
People taking a sauna 4-7 times a week were 61% less likely to suffer a stroke than those taking a sauna once a week. This is the first prospective large-scale study on this topic.
Stroke is one of the leading causes of disability worldwide, placing a heavy human and economic burden on societies. The reduced risk associated with sauna bathing was found by a team of scientists from the Universities of Eastern Finland, Bristol, Leicester, Atlanta, Cambridge and Innsbruck.
The findings are based on the population-based Kuopio Ischaemic Heart Disease Risk Factor (KIHD) study and involved 1,628 men and women aged 53 to 74 years living in the eastern part of Finland. Based on their frequency of taking traditional Finnish sauna baths (relative humidity 10-20%), the study participants were divided into three groups: those taking a sauna once a week, those taking a sauna 2-3 times a week, and those taking a sauna 4-7 times a week.
The more frequently saunas were taken, the lower was the risk of stroke. Compared to people taking one sauna session per week, the risk was decreased by 14% among those with 2-3 sessions and 61% among those with 4-7 sessions. The association persisted even when taking into account conventional stroke risk factors, such as age, sex, diabetes, body mass index, blood lipids, alcohol consumption, physical activity and socio-economic status. The strength of association was similar in men and women.
Previous results from the KIHD study at the University of Eastern Finland have shown that frequent sauna bathing also significantly reduces the risk of cardiovascular and all-cause mortality.
According to the researchers, mechanisms driving the association of sauna bathing with reduced stroke may include a reduction in blood pressure, stimulation of immune system, a positive impact on the autonomic nervous system, and an improved cardiovascular function. In a recent experimental study, the same group of scientists also showed that sauna bathing has acute effects on the stiffness of the arterial wall, hence influencing blood pressure and cardiac function parameters.
Objective: To assess the association between frequency of sauna bathing and risk of future stroke.
Methods: Baseline habits of sauna bathing were assessed in 1,628 adult men and women aged 53–74 years (mean age, 62.7 years) without a known history of stroke in the Finnish Kuopio Ischemic Heart Disease prospective cohort study. Three sauna bathing frequency groups were defined: 1, 2–3, and 4–7 sessions per week. Hazard ratios (HRs) (95% confidence intervals [CIs]) were estimated for incident stroke.
Results: During a median follow-up of 14.9 years, 155 incident stroke events were recorded. Compared with participants who had one sauna bathing session per week, the age- and sex-adjusted HR (95% CI) for stroke was 0.39 (0.18–0.83) for participants who had 4–7 sauna sessions per week. After further adjustment for established cardiovascular risk factors and other potential confounders, the corresponding HR (95% CI) was 0.39 (0.18–0.84) and this remained persistent on additional adjustment for physical activity and socioeconomic status at 0.38 (0.18–0.81). The association between frequency of sauna bathing and risk of stroke was not modified by age, sex, or other clinical characteristics (p for interaction > 0.10 for all subgroups). The association was similar for ischemic stroke but modest for hemorrhagic stroke, which could be attributed to the low event rate (n = 34).
Conclusions: This long-term follow-up study shows that middle-aged to elderly men and women who take frequent sauna baths have a substantially reduced risk of new-onset stroke.
Setor K Kunutsor, Hassan Khan, Francesco Zaccardi, Tanjaniina Laukkanen, Peter Willeit, Jari A Laukkanen