Following on from last week’s blog post about the general health benefits of sauna, today I want to look further into a large study on whether saunas lower Alzheimer’s and dementia risk.  

Study design

The study, published just last year, was conducted on 2315 Finnish men. At the beginning of the study, the men were “apparently healthy” and aged between 42-60 years old. 

The men were followed for an average of 20.7 years (range 18.1-22.6).  Yes, this is a large, long study.

Frequency of sauna use

Based on the frequency of sauna use at the beginning of the study, the participants were categorized into three groups:

1 – average 1 sauna per week

2 – average 2-3 saunas per week

3 – average 4-7 saunas per week. 

You can tell it was done in Finland with those high frequencies of saunas

Measurements

At the beginning of the study, many parameters were measured including blood tests, physical activity, alcohol consumption, smoking, BMI, medication use, cigarette smoking, alcohol consumption, blood pressure, and physical activity. These possible ‘confounding factors’ were measured so that any possible effects of these parameters on the results could be adjusted for.  

At the end of the study, the total number of diagnosed cases of dementia and Alzheimer’s disease were recorded for each group. 

Results

The analysis of the results, adjusted for possible confounding factors showed that, compared to those who used a sauna once a week:

Group 2 – those who had 2-3 saunas a week had a 22% reduction in risk for dementia and a 20% reduction in risk for Alzheimer’s disease.  

You may think this sounds pretty good – but:

Group 3 – those who had 4-7 saunas a week had a 66% reduction in risk of dementia and a 65% reduction in risk for Alzheimer’s disease. 

Study strengths 

  • A large number of participants were included and followed long-term. None of the men were ‘lost’ during the 20 years so there was no missing data. This is due to the fact that in Finland there is a personal identification code and any data on their health is recorded on a national computerized hospital registry. If this study were done in the US, over the 20 year period, many of the subjects would be lost to follow-up and thus their data couldn’t be included. 
  • There were good measurements of baseline risk factors in this study. This means the results could be assessed adjusting for these factors to make sure it wasn’t one of them influencing the results instead of sauna use.

Study limitations

  • As with all observational studies, despite the results being adjusted for possible confounding factors, this study can only show a correlation, rather than causation. What this means is that while the results suggest that sauna use is resulting in risk reduction, is sauna use merely an indicator of a healthy lifestyle? So sauna use correlated with reduced risk but we can’t say it actually caused a reduction in risk. 
  • The frequency of sauna use was measured only at the beginning of the study: A one-time questionnaire. With the study continuing for 20 years, it could well be that the frequency of sauna use was very different for these individuals during this time period. However, we do know that sauna is a huge part of Finnish culture so it wasn’t as if this was an unusual thing for them to do. It is a habit for them.
  • As the majority of Finnish men all use sauna, this study did not compare the regular use of sauna with no sauna use. 
  • Several factors prevent generalization of the study findings: The study was only done in middle-aged Finnish men. Would women show similar results? Would other populations have similar results? The study looked at Finnish sauna bathing. Would other sauna types, steam rooms, hot tubs show similar results?

Conclusion

This study shows promising results for the potential for sauna use to be a protective lifestyle factor for memory disease.  Recommending regular sauna use may prevent or delay the development of dementia and Alzheimer’s disease.  Thus there is a potentially large benefit and small risk if usual precautions for sauna use are followed. 

Additional studies are needed to confirm these results. It will be interesting to see the inclusion of other parameters in these studies in the future, like whether APOE4 gene polymorphisms impact the outcome and further examination of which at risk populations this can help the most. 

Precautions

Remember the precautions for using saunas, from last week’s post:

  1. If you have a health condition, consult with your doctor before you start using saunas
  2. Avoid saunas if you are pregnant
  3. Start slowly – just a few minutes to begin with, then gradually work up how long you stay in the sauna. Typically, this is 20-30 minutes.
  4. Heat responsibly and with someone else. Never alone.
  5. Don’t use a sauna if you have been drinking alcohol. Never consume alcohol while you are in a sauna
  6. Stay hydrated –  before, during and after.
  7. Listen to your body.  Feeling warm and sweaty is OK. Feeling dizzy and nauseous isn’t OK and means you should leave. If you feel uncomfortable, leave.
  8. Don’t eat a huge meal beforehand.
  9. It’s great to do dry brushing beforehand, as this helps with detoxification.
  10. Shower before and after.

Reference

Using sauna 4-7x per week lowered dementia risk by 66% & Alzheimer’s risk by 65% after adjusting for diet/lifestyle.

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