Do heat events pose a greater health risk for individuals with type 2 diabetes?

Chronic medical conditions such as type 2 diabetes may alter the body's normal response to heat. Evidence suggests that the local heat loss response of skin blood flow (SkBF) is affected by diabetes-related impairments in both endothelium-dependent and non-endothelium-dependent mechanisms, resulting in lower elevations in SkBF in response to a heat or pharmacological stimulus. Thermoregulatory sweating may also be diminished by type 2 diabetes, impairing the body's ability to transfer heat from its core to the environment. Diabetes-associated co-morbidities and the medications (particularly those affecting fluid balance) required to treat these conditions may exacerbate the risk of heat-related illness by decreasing SkBF and sweating further. Unfortunately, the majority of studies measure local heat loss responses in the hands and feet and lack measures of core temperature. Therefore, the impact of these impairments on whole-body heat loss remains unknown. This review addresses heat-related vulnerability in individuals with type 2 diabetes by examining the literature related to heat loss responses in this population. Type 2 diabetes, its associated co-morbidities, and the medications required in their treatment may cause dehydration, lower SkBF, and reduced sweating, which could consequently impair thermoregulation. This effect is most evident in individuals with poor blood glucose control. Although type 2 diabetes can be associated with impairments in SkBF and sweating, more physically active individuals requiring fewer medications and having good blood glucose control may be able to tolerate heat as well as those of similar age and body composition.