Heat and cold strain in persons with type 2 diabetes in a changing climate
Both high and low environmental temperatures cause physiological responses intended to lose or preserve body heat that can aggravate the course of chronic diseases and lead to a higher number of health care visits, hospitalizations, or deaths (1). Previous population studies suggests that both exposure to heat and cold among persons with type 2 diabetes is related with higher number of health care visits and mortality (2). High blood pressure (hypertension) often coexists with type 2 diabetes (3) and may further increase vulnerability to high and low environmental temperatures. These populations are likely to suffer even more from the changing climate and the higher number of extreme weathers. These changes are more pronounced in the Arctic compared with other areas (4).
The physiological mechanisms behind the higher vulnerability of people with diabetes to high or low temperatures are not well established.
The aims of the study are to:
Assess how advanced type 2 diabetes in combination with hypertension, influences cardiovascular function and associated neural, and metabolic responses during whole-body passive exposure to heat (increased sweating and skin circulation) and cold (increase in heat production and reduction in skin circulation) compared with healthy people
Examine how diabetic micro- and macrovascular complications involving varying degrees of severity affect the observed cardiovascular, neural, and metabolic functions compared with healthy persons while exposed to heat or cold.
Study design
The data for the study is based on laboratory research material that was collected in Oulu, Finland in 2020. The study population consists of 10 male subjects with advanced T2D and 10 healthy controls (matched for age, BMI, physical activity) who were recruited from the population living in Oulu, Finland. Diabetic complications were assessed from all participants at the Oulu University Hospital Clinic of neurophysiology. These included assessment of cardiovascular autonomic function, thermal thresholds, perception of touch, peripheral vascular disease, kidney function, and retinal images. During the actual experiments the participants were exposed lightly clad in a random order to heat (+40° C) and cold (+10°C) at rest for 90 min. The exposures stimulate cardiovascular function and heat loss responses in heat (sweating, vasodilation) and heat preservation responses in cold (shivering, vasoconstriction). The following parameters were assessed before, during and after the exposures: cardiac function (ECG/arrhythmias, heart rate variability), blood pressure (brachial, central aortic, beat-to-beat), metabolic rate (oxygen consumption), skin temperatures and blood flow (Laser Doppler-flowmetry), amount of sweating, thermal sensations, and comfort. A blood sample was drawn before and after each exposure and from which inflammation markers (CRP, TNFα, IL-6, ET-1), coagulation factors fibrinogen, (FVII, vWF-Akt, D-dimer), lipids (cholesterol, HDL, triglycerides) and glycemic state (glucose, HbA1c) are analyzed.
Relevance of the study
The produced information benefits all populations with type 2 diabetes, and that are occasionally or more prominently, exposed to high and low temperatures. It is especially relevant for the growing working population having diabetes. The changing Arctic climate is likely to bring about more temperature extremes and higher variability in weather rendering preparedness difficult. Most of the temperature-related adverse health effects are preventable. Hence, individuals can utilize the produced research information for appropriate protection and self-treatment of their disease. The produced information provides tools for health care personnel (general medicine, occupational health) for producing advice to their patients for improving protection and treatment. Occupation safety experts can develop plans for improving occupational safety of workers with T2D. Awareness, proper beforehand planning and appropriate protections in environments involving thermal stress assist in reducing morbidity and mortality and the related societal costs.
Place of the work
The Ph.D. candidate is integrated to the research group Occupational Health in the North at the Department of Community Medicine, which consists of interdisciplinary expertise focusing on various occupational health-related topics by combining epidemiological, basic and clinical research.
The Ph.D.-candidate analyzes and prepares scientific reports of the collected data. An important part of the training is practical experience within occupational health and safety by collaborating with relevant external partners, such as an occupational health service, companies with workers exposed to thermal challenges, or the Labour Inspection authority. This will be decided during collaboration wih the PhD-candidate who is also encouraged to collaborate across different disciplines with other PhD-candidates/projects within the Arctic Change doctoral school.