The effect of short-term cold exposure on risk factors for cardiovascular disease.

The aim of this study was to see if a short-term period of exposure to cold in young healthy subjects causes changes in hematological factors known to be associated with the promotion of thrombogenesis. Over a period of 48 hours, changes in the distribution of erythrocytes, granulocytes, and blood platelets, as well as several coagulation, inflammatory, and fibrinolytic parameters, were monitored in 11 young healthy male subjects following a short period (1 hour) of cold exposure (CE) (ambient temperature, 11 degrees C) or exposure to thermoneutral conditions (ambient temperature, 26 degrees C) in winter (November). The major findings were: (1) a CE-induced hemoconcentration as indicated by an increase in erythrocyte count (3.2% increase); (2) after appropriate adjustments for changes in hemoconcentration, a cold-induced mobilization of granulocytes (14.5% increase) and a cold-induced decrease in lymphocytes (7% decrease); (3) thromboxane B2 release following endotoxin stimulation of whole blood was increased by 27.4% in the CE experiments; (4) diurnal rhythms were observed in granulocytes, blood platelets, middle plate volume, tissue plasminogen activator, and plasma activator inhibitor; and (5) CE caused no significant changes in lipopolysaccharide-induced tissue factor, nor in the blood coagulation factor VII or cytokines, interleukin-6, and tumor necrosis factor. It is concluded that short-term cold exposure in young healthy subjects initiates a mild inflammatory reaction and a tendency for an increased state of hypercoagulability.