Abstract
ObjectivePassive heating (PH) has begun to gain research attention as an alternative therapy for cardio-metabolic diseases. Whether PH improves glycaemic control in diabetic and non-diabetic individuals is unknown. This study aims to review and conduct a meta-analysis of published literature relating to PH and glycaemic control.MethodsElectronic data sources, PubMed, Embase and Web of Science from inception to July 2018 were searched for randomised controlled trials (RCT) studying the effect of PH on glycaemic control in diabetic or non-diabetic individuals. To measure the treatment effect, standardised mean differences (SMD) with 95% confidence intervals (CI) were calculated.ResultsFourteen articles were included in the meta-analysis. Following a glucose load, glucose concentration was greater during PH in non-diabetic (SMD 0.75, 95% CI 1.02 to 0.48, P < 0.001) and diabetic individuals (SMD 0.27, 95% CI 0.52 to 0.02, P = 0.030). In non-diabetic individuals, glycaemic control did not differ between PH and control only (SMD 0.11, 95% CI 0.44 to -0.22, P > 0.050) and a glucose challenge given within 24 hours post-heating (SMD 0.30, 95% CI 0.62 to -0.02, P > 0.050).ConclusionPH preceded by a glucose load results in acute glucose intolerance in non-diabetic and diabetic individuals. However, heating a non-diabetic individual without a glucose load appears not to affect glycaemic control. Likewise, a glucose challenge given within 24 hours of a single-bout of heating does not affect glucose tolerance in non-diabetic individuals. Despite the promise PH may hold, no short-term benefit to glucose tolerance is observed in non-diabetic individuals. More research is needed to elucidate whether this alternative therapy benefits diabetic individuals.
Highlights
Frequent passive heating (PH), often referred to as Waon therapy, hot-tub therapy or thermal therapy, may provide health benefits for those who are in diseased and non-diseased states [1,2,3,4,5,6]
Glucose concentration was greater during PH in non-diabetic (SMD 0.75, 95% confidence intervals (CI) 1.02 to 0.48, P < 0.001) and diabetic individuals (SMD 0.27, 95% CI 0.52 to 0.02, P = 0.030)
In non-diabetic individuals, glycaemic control did not differ between PH and control only (SMD 0.11, 95% CI 0.44 to -0.22, P > 0.050) and a glucose challenge given within 24 hours post-heating (SMD 0.30, 95% CI 0.62 to -0.02, P > 0.050)
Summary
Frequent passive heating (PH), often referred to as Waon therapy, hot-tub therapy or thermal therapy, may provide health benefits for those who are in diseased and non-diseased states [1,2,3,4,5,6]. The therapeutic effects of PH on those experiencing poor glycaemic control has not been thoroughly investigated in humans. Glycogen stored in the liver can be released into the bloodstream as blood sugar (glycogenolysis), with cells able to metabolise the glucose or store for later needs. This process maintains blood sugar in between meals but is not as tightly regulated in those with diabetes and poor glycaemic control. In these compromised conditions, blood glucose rises due to the insulin insensitivity, resulting in more insulin being released. Drug therapy is often prescribed but may carry unwanted side effects [27]
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