And the higher the ‘dose,’ the better it seems to be for cardiovascular health, with a daily hot bath seemingly more protective than a once or twice weekly one, the findings indicate.
A linked editorial sounds a note of caution, however, because sudden death associated with hot baths is relatively common in Japan, where the study was conducted. Having a bath is associated with good sleep quality and better self-rated health, but it’s not clear what its long term impact might be on cardiovascular disease risk, including heart attack, sudden cardiac death, and stroke.
The frequency of tub bathing wasn’t associated with a heightened risk of sudden cardiac death, or with a particular type of stroke, called subarachnoid haemorrhage (bleed into the space surrounding the brain).
Further analysis of preferred water temperature indicated 26% lower and 35% lower risks of overall cardiovascular disease for warm and hot water, respectively. But no significant associations emerged for overall stroke risk and water temperature.
After excluding those participants who developed cardiovascular disease within 5 or 10 years of the start of the study, the associations found weren’t quite as strong, but nevertheless still remained statistically significant.
This is an observational study, and as such, can’t establish cause, added to which changes in bathing frequency weren’t tracked during the monitoring period. The typical style of Japanese bathing also includes immersion to shoulder height, and this may be a critical factor.
But, say the researchers, previously published research has pointed to a link between heat exposure and cardiovascular disease prevention: this is because the effects of heat on the body are not dissimilar to those of exercise.
“We found that frequent tub bathing was significantly associated with a lower risk of hypertension, suggesting that a beneficial effect of tub bathing on risk of [cardiovascular disease] may in part be due to a reduced risk of developing hypertension,” write the researchers.