Seasonal variation of some metabolic and haemostatic risk factors in subjects with and without coronary artery disease

Acute myocardial infarction (AMI) is more frequent in winter months than in summer months. The aetiologic mechanisms underlying this seasonal pattern are poorly understood. We investigate whether seasonal variation of metabol ic and haemostatic coronary risk factors exists, and whether this variation is more pronounced in subjects with coronary artery disease (CAD). In 82 s ubjects (47 free of clinical signs of CAD and in 35 survivors of AMI), meas urements of body mass index (BMI), lipoproteins, glucose, insulin, plasmino gen activator inhibitor-1, tissue-type plasminogen activator (t-PA), euglob ulin clot lysis time, fibrinogen, and platelet count were performed twice i n the cold months (December and March) and twice in the warm months (June a nd September). Significantly higher BMI (26.8 versus 26.2 kg/m(2), P < 0.01 ), glucose (5.5 versus 5.1 mmol/l, P < 0.01), total cholesterol (5.61 versu s 5.32 mmol/l, P < 0.05), low-density lipoprotein cholesterol (3.63 versus 3.34 mmol/l, P < 0.05), triglycerides (1.79 versus 1.61 mmol/l, P < 0.01), Lp(a) (270.7 versus 237.5 mg/l, P < 0.01), fibrinogen level (3.50 versus 2. 95 g/l, P < 0.00001), platelet count (212 X 10(9) versus 173 X 10(9)/l, P < 0.01) and significantly lower high-density lipoprotein cholesterol level ( 1.22 versus 1.28 mmol/l, P < 0.05) were observed in the cold months compare d with the warm months. Significant seasonal variation of t-PA activity (1. 19 versus 0.87 IU/ml, P = 0.015) and t-PA antigen (8.5 versus 7.3 ng/ml, P = 0.05) was demonstrated only in subjects with CAD. Clustering of peak valu es of several metabolic and haemostatic coronary risk factors was observed in winter months. This variation might be of aetiopathogenetic importance f or the seasonal pattern of acute myocardial infarction. <(c)> 2001 Lippinco tt Williams & Wilkins.