The Relationship Between Hemodynamic Reactions to Cold Stress and Changesof Salivary Cortisol Levels
An experimental study was conducted with the participation of 30 healthy male volunteers (18–20 years) in order to determine the types of hemodynamic reactions to the general cooling of the body and to determine the severity of cold stress from the dynamics of salivary cortisol levels. The experiment included three 10-minute stages: rest t  = 20°С; being in a cold chamber t = –20°С; warming t = 20°С. During each stage, blood pressure (BP), heart rate (HR), temperature in the ear canal were determined, and saliva samples were taken for subsequent determination of free cortisol levels. Volunteers were divided into two groups according to the dynamics of changes in salivary cortisol during cooling: with an increase (n = 22) and a decrease (n = 8) in the hormone's level. It was shown that during cooling the body temperature of the subjects significantly decreased by an average of 2.1–2.3°С and did not reach the initial values by the end of the warming stage. In both groups of individuals, when cooling, an increase in BP and a decrease in HR occurred, while in the group with an increase in cortisol, significantly higher levels of systolic BP and a slight decrease in HR were detected. During warming, the hemodynamic indices tended to the initial levels, and the change in the salivary cortisol level was similar to that during cooling. Thus, an increase in the level of salivary cortisol during short-term (10 min) cooling of the human body is associated with severe cold arterial hypertension, a lower baroreflex response, and the risk of cold damage to blood vessels. A decrease in salivary cortisol as a reflection of a decrease in the release of free hormone into the cell during cold stress, in combination with moderate cold arterial hypertension, may indicate a successful adaptation of the body to cold with limited development of hypothermia.