Effects of sodium bicarbonate bath on the quality of sleep: An assessor-blinded, randomized, controlled, pilot clinical trial

Background: Sleep is fundamental to a healthy life, and sleep disorders are an important health issue in healthcare. Whole-body warm water bathing is a non-pharmacological, safe (non-invasive), and widely used method for comforting. Here, we explored the feasibility and preliminary effectiveness of sodium bicarbonate bath (SBB) on sleep quality. Methods: Healthy adults without sleep disturbances were randomly assigned to shower baths (SHB), tap-water baths (TWB, placebo tablets), or SBB. All participants took a bath (shower, tap-water, or SBB) once a day for 10 min, after dinner, for 7 days. Sleepscan-derived sleep parameters, including total sleep time (TST), symptom questionnaires, and salivary alpha-amylase concentration were evaluated as outcome measures. Results: Forty participants were enrolled (14, 13, and 13 in SHB, TWB, and SBB groups, respectively) and 38 participants completed the trial (13, 12, and 13, respectively). The recruitment, adherence, and completion rates were 90.9% (40/44), 95.0% (38/40), and 95.0% (38/40), respectively. The SBB group showed a significant increase (12.35 [mean]+/- 10.07 [standard deviation] min) in the mean TST at 1-week post-intervention (p = 0.0041) than the SHB (-1.81 +/- 14.58 min; p = 0.0231) and TWB (4.54 +/- 10.97 min; p = 0.0377) groups. The TST scores at 1-week post-intervention, sleep onset latency, wake after sleep onset, and sleep efficiency were significantly different between the groups. Sleep satisfaction by questionnaire was significantly improved with intervention in the SBB group than that in the SHB and TWB groups. Salivary alpha-amylase levels significantly improved in the SBB and TWB groups than in the SHB group, with the change being greater in the SBB group. Conclusions: SBB for 7 days had positive effects that improved sleep quality of adults. Further studies are needed to examine the efficacy and safety of SBB for prolonged usage in people diagnosed with insomnia, using objective sleep measurements, and to investigate potential sleep-enhancing mechanisms of action.