Seasonal variation in thrombotic and thrombolytic factors in human plasma

Abstract

Thrombotic diseases have been shown to increase in the winter. This study sought to examine four thrombotic factors; Fibrinogen (Fb), Factor VII (FVII), Factor X (FX) and Tissue Plasminogen Activator Inhibitor (TPA‐I), and two thrombolytic factors Antithrombin III (ATIII) and Tissue Plasminogen Activator (TPA) in human plasma during winter and summer. To date, no comprehensive studies exist that look at these clotting factors simultaneously. Sandwich ELISA was used to measure the concentration of each factor from individual subjects. Statistical significance was found in seasonal variation of Fb, FVII, FX and TPA‐I (limited to females). A lower concentration of Fibrinogen was found in the winter, which was unexpected, but consistent with other studies. FVII increased in the winter, consistent with our original hypothesis. FX showed lower concentrations in the winter, which has not been previously reported in the literature. TPA‐I showed a marked increase in the summer but this increase was limited to females over 40. Neither TPA, nor ATIII showed significant seasonal variation. We conclude from this that a number of thrombotic factors increase in the winter but this is not consistent among all factors measured. Thrombolytic factors were unchanged. This research was supported by the Saint Mary's College of California Faculty‐Alumni Grant, Faculty Development Grant, and the Summer Research Program