Abstract
Frequent bathtub bathing (BB) improves sleep quality and mental health of middle-aged and older Japanese individuals. This study investigated the chronic effects of BB with and without a bath additive (bathtub bathing with KIKIYU [BBK]) in healthy young adults. The study involved healthy young adults who habitually showered, as opposed to bathing. Nineteen participants were randomly assigned to either the BB or BBK groups for 14 consecutive nights. After a 2-week washout period (shower bathing), the participants were asked to switch their bathing styles (a crossover design). The artificial bath additive for the BBK group contained inorganic salts and carbon dioxide. The participants were evaluated by using the Oguri-Shirakawa-Azumi Sleep Inventory-Middle-aged version (OSA-MA) and 1-ch sleep electroencephalography (EEG) for sleep quality, the Profile of Mood States (POMS), Self-rating Depression Scale (SDS), and Apathy Scale (AS) for mental conditions.
Sleepiness on waking and refreshing scores in the OSA-MA significantly differed between the shower bathing and BBK groups. EEG results did not significantly differ among the bathing styles. Vigor T-score and total mood disturbance (TMD) scores showed significant differences in the two bathing groups (shower vs. bathing), and fatigue T-score was significantly lower in the BBK group compared with both the BB and shower groups. SDS score was significantly lower in the BBK group compared with the shower group. AS score was significantly lower in the two bathing groups (shower vs. bathing).
The OSA-MA score was possibly influenced by vasodilatation and circulation by using carbon dioxide and keeping the body warm after bathing by using inorganic salts. The OSA-MA score was possible also affected by fatigue alleviation and maintenance of vitality by using a citrus lemon scent and yellow-green hue. Furthermore, frequent body heating affects the central nervous function related to mood and emotion.
Based on these results, we can conclude that BB and BBK prior to shower bathing improved the mental health of the young adults in this study.
