SEASONAL-VARIATION IN FIBRINOGEN IN THE ROTTERDAM STUDY

As evidence accumulates to implicate fibrinogen as a risk indicator fo r cardiovascular disease, it is of interest to study its seasonal vari ation. A population based cross-sectional study was performed among pa rticipants of the Rotterdam Study, a cohort of 7,983 men and women, ag ed 55 years and over, Fibrinogen levels were measured by the prothromb in time derived method in the first 2,325 participants of the study. F ibrinogen levels were considerably higher in winter. The seasonal diff erence was 0.34 g/l (95% confidence interval 0.29, 0.39) and was more pronounced in subjects aged 75 years and over than in subjects aged 55 to 75 years, 0.43 g/l (0.34, 0.52) and 0.29 g/l (0.24, 0.35), respect ively . Additional adjustment for body mass index, systolic and diasto lic blood pressure, and total and HDL cholesterol did not materially c hange the findings. After adjustment for seasons, outdoor temperature was not associated with fibrinogen. Adjustment for outdoor temperature did not change the seasonal variation of fibrinogen, seasonal differe nce 0.31 g/l (0.24, 0.37). In conclusion, fibrinogen levels are highes t in Winter. The seasonal Variation of fibrinogen is more pronounced i n the elderly. Outdoor temperature does not seem to play a role in the seasonal variation of fibrinogen. Seasonal variation of fibrinogen ma y partly explain the increased cardiovascular disease mortality in Win ter.