Among middle-aged Japanese adults, tub bathing was associated with a reduction in CVD and stroke, according to research published in Heart.
Researchers observed that among participants aged 40 to 59 years with no prior CVD, compared with participants who reported taking tub baths two times or fewer per week, participants who reported taking tub baths almost daily experienced reductions in:
- total CVD (HR = 0.72; 95% CI, 0.62-0.84);
- CHD (HR = 0.65; 95% CI, 0.45-0.94);
- total stroke (HR = 0.74; 95% CI, 0.62-0.87);
- cerebral infarction (HR = 0.77; 95% CI, 0.62-0.97); and
- intracerebral hemorrhage (HR = 0.54; 95% CI, 0.4-0.73).
The cohort of 30,076 participants was followed up between 1990 and 2009, translating to 538,373 person-years of follow-up. Researchers observed no associations between the frequency of tub bathing and risk for sudden cardiac death or subarachnoid hemorrhage.
Among individuals who tub bathe on a regular basis, researchers observed reductions in CVD, CHD and total stroke.
“A variety of studies have addressed the mechanisms by which heat exposure plays a role in preventing CVD,” Tomohiko Ukai, MPH, of the division of public health at Osaka Prefectural Institute of Public Health, Japan, and colleagues wrote. “Heat exposure increases core body temperature, cardiac contractility, heart rate and blood flow, and decreases vessel endothelial shear stress. These effects are similar to the impact of exercise and are believed to improve vascular function over the long term.”
Tub bathing and hypertension
After adjustment for age and sex, compared with those who bathed in a tub two times or fewer per week, those who bathed almost daily had lower risk for hypertension (adjusted OR = 0.8; 95% CI, 0.65-0.98), as did those who bathed three or four times per week (aOR = 0.8; 95% CI, 0.67-0.96). There was no difference between the groups in risk for diabetes or hypercholesterolemia.
“The potential beneficial effect of tub bathing of CVD events may be mediated by the reduced development of major cardiovascular risk factors in those who took a tub bath frequently,” the researchers wrote. “We found that the frequent tub bathing was significantly associated with a lower risk of hypertension, suggesting that a beneficial effect of tub bathing on risk of CVD may be in part due to a reduced risk of developing hypertension.”
Bath temperature and CV health
“The typical Japanese style of bathing involves filling the tub to shoulder depth with hot water at approximately 40°C-42°C, while some prefer temperatures upward of 43°C,” the researchers wrote.
“The negative aspect of tub bathing is that it can cause heatstroke more frequently when the tub water temperature is too high,” the researchers wrote. “In our research, we asked participants to subjectively describe their tub water temperature (lukewarm, warm or hot). However, we observed no significant difference in the inverse association between tub bathing frequency and risk of CVD by the water temperature. Our results did not suggest any preferable water temperature, but further research regarding the water temperature is warranted.” – by Scott Buzby
Disclosures: The authors report no relevant financial disclosures.