Habitual Hot-Tub Bathing and Cardiovascular Risk Factors in Patients With Type 2 Diabetes Mellitus: A Cross-Sectional Study

Background: Several studies suggested that heat therapy, including sauna or hot-tub bathing, was associated with improved glycemia and other risk factors for cardiovascular diseases. This study aimed to assess the influences of the habit of hot-tub bathing on cardiovascular risk factors in patients with type 2 diabetes in a real-world setting. Methods: In this cross-sectional study, we enrolled the patients with type 2 diabetes who regularly visited the outpatient clinic between October 2018 and March 2019. We obtained the information on the habit of hot-tub bathing by using a self-reported questionnaire. The results of anthropometric measurements, blood tests and medications were obtained from the medical charts. We divided the patients into three groups according to the frequency of hot-tub bathing as follows; group 1: >= 4 times a week, group 2: < 4 times a week, >= 1 time a week, group 3: < 1 time a week. The biomarkers were compared among the groups by one-way analysis of variance. Multiple linear regression analyses were performed to adjust for confounding variables. Results: We enrolled 1,297 patients. There were significant differences in body mass index (group 1 : 25.5 +/- 5.0, group 2: 26.0 +/- 5.4, group 3: 26.7 +/- 6.0, P = 0.025), diastolic blood pressure (73 +/- 12, 75 +/- 12, 77 +/- 13, P = 0.001) and hemoglobin A1c (7.10 +/- 0.97, 7.20 +/- 1.11, 7.36 +/- 1.67, P = 0.012). Multiple regression analysis revealed that the frequency of hot-tub bathing was a significant determinant of hemoglobin A1c, body mass index and diastolic blood pressure. Conclusions: In this real-world study, habitual hot-tub bathing was associated with slight improvements in glycemia, obesity and diastolic blood pressure, and thus, can be a possible lifestyle intervention in patients with type 2 diabetes.