ABSTRACT
In healthy individuals, an efficient regulatory heat system enables the body to cope effectively with thermal stress. Within certain limits, thermal comfort can be maintained by appropriate thermoregulatory responses and physical and mental activities can be pursued without any detriment to health. Temperatures exceeding the comfortable limits, both in the cold and warm range, substantially increase the risk of (predominantly cardiopulmonary) deaths. Several mechanisms may explain this increased mortality: increased blood pressure, blood viscosity, and heart rate, associated with physiological adjustment to cold and warmth, may explain the temperature-induced increased mortality of diseases of the cardiovascular system (Keatinge et al., 1984; Pan et al., 1995). Indirectly, influenza contributes to cold-related mortality (Anderson & Le Richie, 1970; Kunst et al., 1993). Susceptibility to pulmonary infections may increase through bronchoconstriction, caused by the breathing of cold air (Schaanning, et al., 1986). Bull (1980) argues that excess mortality in winter may be due to physiological changes in cellular and humoral immunity, with behavioural factors also playing a role.
