Regular tub bathing is connected to a reduced risk of death from stroke and heart disease.

Japanese scientists have done a large scale and peer-reviewed study on the long-term effects of tub bathing concerning cardiovascular disease risk. The research and its results have been published in the science journal: Heart.

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The scientists conclude that habitual tub bathing is connected to a reduced risk of death from stroke and heart disease. Even more interesting is the fact that it seems that a higher 'dose' (meaning more frequent bathing) turns out to be even more protective than just bathing merely one or two times a week.

Although sudden death associated with a hot bath is relatively common in the area where the study was carried out (Japan), tub bathing is deemed to have a preventive effect against cardiovascular disease (CVD) by enhancing hemodynamic function (better blood flow). Additionally, it is known that taking a bath helps people sleep better. However, it is not clear what its long term effects may be on cardiovascular disease risks like strokes, heart attacks, and sudden cardiac deaths. This is what the scientists set out to find out.

In total little over 30.000 people participated with an age range of 40 to 59 years and no history of cardiovascular disease. The participants were followed for an extended period of 19 years (from 1990 to 2009). they were categorized by bathing frequency: Ranging from every day to three to four times a week all the way down to zero or two times per week.

During the beginning of the study, approximately 40,000 partakers filled out a comprehensive survey on their bathing habits and possibly influential factors such as exercise, diet, alcohol intake, average daily sleep time, and weight as well as current use of medicines and medical history.

Subsequently, every participant was observed until the completion of the study or death. The final report is based on 30,076 people.. During the monitoring phase, 2097 instances of cardiovascular disease were detected: 1769 strokes, 275 heart attacks, and 53 sudden cardiac deaths.

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Following correction for possible influencing factors, a review of the data revealed that in the comparison between a once or twice weekly bath or no bath at all, a daily hot bath was linked with a rather impressive 28% reduced general risk of cardiovascular disease as well as 26% reduction in the overall risk of stroke. The amount of bathing was not connected to an increased risk of sudden cardiac death, or with a particular type of stroke, called a subarachnoid haemorrhage.

The researchers went one step further and made and investigated the preferred water temperature, which showed 26% lower risks of overall cardiovascular disease for warm water and a 35% lower risk for hot water. However, no substantial relationships became apparent for general stroke risk and water temperature.

The connections to reduced risk became less apparent when excluding people that developed cardiovascular disease during the period of 5 or 10 years after the commencement of the research. Notwithstanding, even after excluding those participants, the results still remained significant. Because of the fact that the study is based on observational research, it cannot confirm cause, added to which modifications in bathing frequency were not followed through the tracking period.

The researchers stated in a written statement that they found that the link between routine tub bathing with a lower risk of hypertension was substantial. Implying that an advantageous effect of bathing on risk of CVD might be partly because of a decreased risk of developing hypertension.

It should be noted that the scientists expressed that there are some risks involved with taking a very hot bath. Dr. Andrew Felxi Burden stated on the matter that there should be no doubt regarding the possible hazards of bathing in hot water. It turns out that the occurrence of death from this heightens with age, as well as with the temperature of the water. He added that cardiovascular disease itself is not very likely to be the reason for these deaths. Instead, he suggests that it is more like that these deaths are the result of overheating, resulting in confusion and drowning. Caution on this matter is required, and further research into possible cardiovascular benefits of heat-free baths is needed.

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Sources and further reading: Habitual tub bathing and risks of incident coronary heart disease and stroke / Tub bathing and heart disease / BMJ press release