SEASONAL-VARIATIONS OF RHEOLOGICAL AND HEMOSTATIC PARAMETERS AND ACUTE-PHASE REACTANTS IN YOUNG, HEALTHY-SUBJECTS

The incidence of cardiovascular diseases is increased in winter months . Recent studies have shown seasonal changes in plasma viscosity, fibr inogen, and factor VII activity with elevated levels during winter. An increase in these factors generates a ''hypercoagulable state,'' whic h may lead to a rise in cardiovascular morbidity and mortality. It has been suggested that an increase in upper respiratory infections might be the underlying cause for the raised acute-phase reactants, in part icular fibrinogen, during the winter season. We investigated seasonal variations of 26 parameters, determining blood rheology and hemostasis in 16 healthy volunteers (8 men and 8 women) aged 20 to 41 years. The y were seen at monthly intervals over a period of 1 year. Seasonal var iation with peak fitted values in the winter months was found for plas ma viscosity (P<.001 for the seasonal difference), red blood cell defo rmability (P<.001), whole blood viscosity (P<.001), hemoglobin (P<.001 ), hematocrit (P<.001), mean corpuscular volume (P=.001), platelet cou nt (P=.01), alpha 1-glycoprotein (P<.001), fibrinogen (measured by imm unonephelometry; P<.001), plasminogen activator inhibitor-1 (P=.002), LDL cholesterol (P=.003), and triglyceride levels (P<.001). HDL choles terol (P<.001) and cortisol (P=.001) showed inverse seasonal patterns, with a maximum during summertime. No statistically significant season al variations were seen for red blood cell aggregation, complement fac tor C4, total cholesterol, ceruloplasmin, haptoglobin, white blood cel l count, and plasminogen. These data do not support the hypothesis tha t increased morbidity and mortality from cardiovascular diseases durin g winter may be mainly attributable to increased synthesis of acute-ph ase proteins due to infections, The cause for the seasonal variations in rheological and hemostatic parameters remains unclear and should be studied in more detail.