A randomised intervention study from Japan has compared the physical and mental health effects of daily full-immersion bathing with showering. The participant-reported results found here add practical insight to theories in favour of immersion bathing.
There are many lifestyle choices that have a direct impact on our health, such as smoking, exercise and diet. Could your bathing routine also be added to that list? Immersion of the body in water (immersion bathing), rather than showering, causes greater dilation of blood vessels. Subsequently, there is improved replenishment of oxygen and nutrients to peripheral areas, together with better removal of carbon dioxide and other waste products, which refreshes the body.
In Japan, full-immersion bathing is a more common habit than in other countries, where showering prevails. A research group in Japan (Goto et al.) investigates the effects of immersion bathing against that of showering. The team’s previous studies recruited a cross-section of the Japanese population that immersion bathed daily – and the participants reported improved happiness, sleep and general health status, and reduced stress levels too. However, in their latest study, Goto et al. conducted a clinical trial that compared the effects of immersion bathing versus showering over a period of time.
The team conducted a randomised controlled trial involving 38 participants that were equally split into two groups. One group exclusively had 10-minute immersion baths once daily for two weeks, followed by two weeks of exclusive showering, and vice-versa for the other group. Participants would then report daily on several aspects of their mental and physical health before and after either the bathing or showering routine.
Firstly, the participants self-reported on the following aspects before and after taking either a shower or bath: general health, skin condition, fatigue, stress, pain and ‘smile in the mirror’. Unsurprisingly, the averaged results demonstrated statistically significant improvements reported for all aspects after having either a shower or a bath. The amount of improvement for bathing was greater than for showering for all reported items, however the investigators did not determine if the differences were statistically significant. Instead, Goto et al. asked the participants to retrospectively self-report on all the items after each two-week period of either bathing or showering. After bathing intervention, scores for fatigue, stress and pain were significantly lower, and ‘smile’ scored significantly higher, when compared to showering. General health, and skin condition also improved after bathing, but not to a statistically significant level.
The team also investigated the difference in mood states after 2 weeks of showering or bathing. They used Profile of Mood States (POMS) scores to determine this – POMS is used worldwide, and measures tension-anxiety, depression-dejection, anger-hostility, fatigue, confusion, and vigour. Following the bathing intervention, POMS scores for tension-anxiety, depression-dejection, and anger-hostility were significantly lower compared to the showering intervention.
This study advances the theoretical knowledge of the benefits of bathing over showering by reporting self-assessment findings from an interventional clinical trial. The decreased fatigue and improved general health scores observed from bathing intervention could be due to improved metabolic action from bathing. Also, the relaxing effect of bathing on muscles and joints may contribute to the decreased pain scores reported in this study. Therefore, the results from this investigation are beneficial – however, it is always important to address this study’s limitations:
- The sample size is small – only 38 participants (with 5 withdrawals)
- The trial was conducted in autumn, and so did not take seasonal differences into account
- The timing of either the bathing or showering routine could not be strictly regulated
- Generally, the Japanese population like immersion bathing more than other nations, and so these findings could be different if the study was conducted in Europe for example
Nevertheless, this trial has laid a positive foundation for future studies. Also, the longitudinal structure to this trial is a positive – all participants experienced both bathing and showering, making it more likely that reported differences are due to immersion bathing causing them.