Blunted cardiovascular responses in individuals with type 2 diabetes and hypertension during cold and heat exposure

Mojdeh Rafieian¹Erlend Hoftun Farbu¹Anje Christina Höper^1,2Rasmus Valtonen^3,4Henna Hyrkäs-Palmu⁵Juha Perkiömäki^3,4Craig Crandall⁶Jouni Jaakkola⁵Tiina Maria Ikäheimo^1,7*

• ¹Department of Community Medicine, Faculty of Health Sciences, UiT The Arctic University of Norway, Tromsø, Troms, Norway
• ²Department of Occupational and Environmental Medicine, University Hospital of North Norway, Tromsø, Troms, Norway
• ³Research Unit of Biomedicine, Faculty of Medicine, University of Oulu, Oulu, Northern Ostrobothnia, Finland
• ⁴Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland, Oulu, Finland
• ⁵Research Unit of Population Health, Faculty of Medicine, University of Oulu, Oulu, Northern Ostrobothnia, Finland
• ⁶Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, Texas, USA, Texas, United States
• ⁷Research Unit of Population Health, University of Oulu, Oulu, Finland, Oulu, Finland

Introduction: The effect of type 2 diabetes (T2D) on indices of cardiovascular function during exposure to cold or hot environmental temperatures is not well known. Therefore, the aim of our study was to assess the effect of short-term whole-body cold and heat exposure on the cardiovascular responses in individuals with T2D.Material and methods: 20 participants aged 40-79 years (10 T2D with hypertension, and 10 controls) underwent 90 minutes of whole-body exposure to cold (10°C; 10% relative humidity) and heat (40°C; 50% relative humidity) in a randomized sequence on differing days. Central and brachial blood pressure (BP), heart rate (HR), and skin blood flow were measured before, during, and after the exposure. Results: During cold exposure, subjects with T2D exhibited a smaller increase in central (14 (CI 95%:3, 23) vs. 43 (CI 95%:32, 53) mmHg, p < 0.05) and brachial systolic BP (12 (CI 95%:1, 22)) vs. 40 (CI 95%:30, 51) mm Hg, p < 0.05) compared to controls. The corresponding reduction in HR in the cold was also less in T2D compared to controls (5 (CI 95%:-10 , 0.02) vs. 9 (CI 95%:-14, -4) bpm, p < 0.05). Heat exposure reduced central and brachial BP similarly in both groups. However, the heatrelated increase in HR was less pronounced in T2D subjects compared to controls (7 (CI 95%:1, 13) vs. 14 (CI 95%: 9, 19) bpm, p < 0.05). Finally, the magnitude of the increase in skin blood flow was less in the heat in T2D subjects (+210 (CI 95%:-41, 461) vs. +605 (CI 95%: 353, 855) PU, p < 0.05).Discussion: T2D attenuated cardiovascular responses, such as BP and HR during short-term exposure to cold, and HR and skin blood flow during short-term exposure to heat. These observations suggest impaired capacity to respond to environmental temperature extremes in individuals with T2D.