Seasonal changes in haemostatic factors in young and elderly subjects.

Morbidity and mortality from cardiovascular disease are more common in colder seasons, especially in elderly people. Previous studies have shown higher fibrinogen levels in old people in the winter months. The present studies of haemostatic factors in relation to age and season have shown that fibrinogen, tissue plasminogen activator (tPA), protein S and protein C levels are higher in old (aged 75 years and over) than young (aged 25-30 years) subjects while antiplasmin levels are lower in old people. Antiplasmin and protein C levels are lower in winter in both young and old while plasminogen activator inhibitor (PAI) is higher, and tPA higher in old people only. This study illustrates the complex interrelationships of the haemostatic system and may suggest that in 'successful' elderly people the fibrinolytic system may alter to maintain the delicate balance between thrombogenic and fibrinolytic activity. Nevertheless, the results presented here suggest that both old age and cold weather may increase the risk of atherothrombotic disease.