Exposure to cold and respiratory tract infections.

There is a constant increase in hospitalizations and mortality during winter months; cardiovascular diseases as well as respiratory infections are responsible for a large proportion of this added morbidity and mortality. Exposure to cold has often been associated with increased incidence and severity of respiratory tract infections. The data available suggest that exposure to cold, either through exposure to low environmental temperatures or during induced hypothermia, increases the risk of developing upper and lower respiratory tract infections and dying from them; in addition, the longer the duration of exposure the higher the risk of infection. Although not all studies agree, most of the available evidence from laboratory and clinical studies suggests that inhaled cold air, cooling of the body surface and cold stress induced by lowering the core body temperature cause pathophysiological responses such as vasoconstriction in the respiratory tract mucosa and suppression of immune responses, which are responsible for increased susceptibility to infections. The general public and public health authorities should therefore keep this in mind and take appropriate measures to prevent increases in morbidity and mortality during winter due to respiratory infections.