Seasonal changes in platelets, fibrinogen and factor VII in elderly people

Background: an increase in mean platelet volume and a decrease in platelet total have been reported following stroke and increased mean platelet volume in acute myocardial infarction has been shown to be predictive of mortality. Objective: given the established seasonal variation in morbidity and mortality from cardiovascular disease and various risk factors for the disease, we explored the seasonal variation in mean platelet volume and platelet total. Methods: we assessed levels of platelet count, platelet volume, fibrinogen, factor VII, core body and ambient temperatures in 54 healthy community dwelling elderly volunteers over a period of 1 year. We used cosinor rhythmometry to quantify and compare the seasonal rhythms. Results: we found significant seasonal variation in fibrinogen, mean platelet volume and core body temperature an of which peaked synchronously in May/June, in a year with an atypically mild winter and hot summer. Platelet total and factor VII did not exhibit a seasonal rhythm. Conclusions: we conclude that the synchrony between peak size of platelets and peak level of fibrinogen will significantly increase the likelihood of thrombotic events. These results provide further evidence of a seasonal pro-thrombotic state, which has a complex relationship with temperature.