SEASONAL DIFFERENCES IN BLOOD-CELL PARAMETERS AND THE ASSOCIATION WITH CIGARETTE-SMOKING

Seasonal changes in red cell parameters need to be defined in order to properly interpret laboratory results. In this study blood counts wer e obtained prospectively in 104 healthy men (84 non-smokers and 20 smo kers) aged 28-63 years during the summer and winter months. Seasonal c hanges in plasma volume were also calculated. In healthy non-smokers, their haemoglobin concentration and haematocrit ratio were lower in su mmer than in winter with a concomitant 5.5% increase in plasma volume. In smokers, there was no change in plasma volume, but haematocrit lev els increased in summer. We conclude that both smoking status and seas onal variation should be taken into account in the evaluation of blood count results, Further studies are warranted to determine if our resu lts can be extrapolated to subjects of both sexes and of various ages exposed to different climatic conditions.