Habitual hot water bathing protects cardiovascular function in middle-aged to elderly Japanese subjects

Favorable effects of sauna bathing on cardiovascular disease have been demonstrated. Hot water bathing is an alternative, and could also have similar effects. Information pertaining to hot water bathing frequency and water temperature was obtained from 873 subjects. Carotid mean and max intima-media thickness (I MT) and brachial-ankle pulse wave velocity (baPWV) were measured as indices of atherosclerosis. Central haemodynamics were evaluated using radial pulse waveform analyses. Plasma levels of B-type natriuretic peptide (BNP) were measured as an index for cardiac loading. The mean duration of a single hot bath was 12.4 +/- 9.9 min. Subject bathing in hot water >= 5 times per week had significantly lower baPWV, central pulse pressure (PP), and BNP after correcting for possible confounding parameters. Stepwise regression analyses revealed that hot water temperature was negatively associated with baPWV, while bathing frequency was negatively related to central PP and BNP. A longitudinal follow-up in 164 subjects showed that hot water bathing >= 5 times per week was associated with significantly lower increase in BNP overtime, while the temperature of the water tended to be related to lower increases in carotid max IMT and baPWV. Hot water bathing showed a favorable effect on atherosclerotic and central haemodynamic parameters.