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 ho urs, changes in the distribution of erythrocytes, granulocytes, and blood p latelets, as well as several coagulation, inflammatory, and fibrinolytic pa rameters, were monitored in 11 young healthy male subjects following a shor t 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 hemoconce ntration 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 de crease in lymphocytes (7% decrease); (3) thromboxane B-2 release following endotoxin stimulation of whole blood was increased by 27.4% in the CE exper iments; (4) diurnal rhythms were observed in granulocytes, blood platelets, middle plate volume, tissue plasminogen activator, and plasma activator in hibitor; and (5) CE caused no significant changes in lipopolysaccharide-ind uced tissue factor, nor in the blood coagulation factor VII or cytokines, i nterleukin-6, and tumor necrosis factor, It is concluded that short-term co ld exposure in young healthy subjects initiates a mild inflammatory reactio n and a tendency for an increased state of hypercoagulability. (C) 1999 Els evier Science Ltd. All rights reserved.