Frequent hot baths tied to better health in patients with T2D

Taking regular hot baths may have a positive impact on glycaemia, blood pressure (BP), and body weight among Japanese patients with type 2 diabetes(T2D), according to a real-world study touted as the first to analyse the effect of heat therapy in T2D.

“Our analysis demonstrated that the frequency of hot tub bathing could have beneficial influences on glucose control, hypertension, and obesity even after adjusting for confounding factors,” said study investigator Dr Hisayuki Katsuyama from Kohnodai Hospital, Ichikawa, Chiba, Japan, who presented the findings as a poster at the recent EASD meeting, held virtually this year. [EASD 2020, abstract 342]

“Heat therapy in the form of hot tub bathing can be an effective therapeutic option for patients with T2D,” he emphasized.

No large studies on hot baths in diabetes

Until the current study, there were no large studies looking at the effects of regular hot tub bathing on metabolic parameters in diabetes, said Katsuyama.

A previous study in T2D patients showed a significant reduction in fasting glucose and HbA_1c  with hot tub therapy lasting 30 minutes each day for six days, and up to 3 weeks. Researchers said the benefits could be due to increased blood flow to the skeletal muscles. However, the study was small, with only eight patients included. [N Engl J Med 1999;341:924-925]

Why the regular hot baths

Taking a regular hot bath is integral to Japanese. Hot baths are thought to help improve blood circulation and relieve stress, among other benefits. This prompted Katsuyama to conduct the study in his own country.

Using a self-reported questionnaire, he and his team investigated the frequency of hot-tub bathing in 1,297 Japanese patients with T2D who regularly visited the Kohnodai Hospital over 6 months.

Patients were divided into three groups based on the frequency of hot tub bathing: group 1 (≥4 baths per week, n=693); group 2 (1 to <4 baths per week, n=415); and group 3 (<1 bath per week, n=189). Mean age of the patients was 67 years, weight was 67 kg. Mean BMI was 25.9 kg/m²,  and HbA_1c was 7.2 percent. There were more men than women (713 vs 584) in the cohort.

The mean frequency of bathing was 4.2 times a week; mean duration of bathing was 16 minutes.

Patients who bathed more often (group 1) had lower BMI, waist circumference, diastolic BP, and HBA_1c compared to groups 2 and 3.

Benefits may be similar to exercise

“Daily heat exposure by hot tub bathing may be beneficial particularly for patients who are unable to exercise,” Katsuyama said. “It may be similar to the benefits they get from exercise,” which may help to improve insulin sensitivity and enhance energy expenditure.  

He said the relatively large number of participants was a key strength of the study. One limitation though was the cross-sectional nature of the study. “We cannot guarantee causality, and various confounding factors, such as diet and other life habits, could influence the results,” he added.