Repeated heat exposure like
sauna bathing is suggested to beneficially affect against
dementia development. The epidemiological evidence is, however, scarce. Therefore, we studied the association between heat exposure during
sauna bathing (i.e., the frequency of
sauna bathing, frequency of heat sessions,
length of stay in heat,
sauna temperature) and the subsequent risk of
dementia. A prospective cohort study was conducted based on 13,994 men and women aged 30-69 and free from
dementia diagnosis from the Finnish Mobile Clinic Follow-up Survey. During a follow-up of 39 years, a total of 1805
dementia patients were diagnosed. The
sauna bathing data was gathered from a questionnaire. Analyses based on the Cox model included the
sauna bathing variables and the potential confounding factors.
Sauna bathing frequency was related to a reduced risk of
dementia after adjustment for the potential sociodemographic, lifestyle, and metabolic risk factors of
dementia considered. The hazard ratio of
dementia between individuals
sauna bathing 9-12 times per month in comparison with those not
sauna bathing or
sauna bathing less than four times per month was 0.47 (95% CI = 0.25-0.88) during the first 20 years of follow-up and 0.81 (95% CI = 0.69-0.97) during the whole follow-up. The results are in line with the hypothesis that
sauna bathing provides protection against
dementia. Further studies are required to verify the suggested benefits of
sauna bathing.