We appreciate the comments of Manfredini and Boari and Donahoo and Eckel. Regarding the letter of Manfredini and Boari, we consider high cholesterol level to be a chronic risk factor for the development of coronary heart disease. However, the epidemiological observation of increased mortality from coronary heart disease in the winter could be related to a “clustering of peak values of haemostatic coronary risk factors,”1 which in turn might be linked to winter hemoconcentration. We are currently analyzing data from a substudy within the SEASON study data set,2 further exploring seasonal variation in fibrinogen levels and its relationship to changes in plasma volume (PV).
Ockene IS, Chiriboga DE, Stanek EJ, Harmatz MG, Nicolosi R, Saperia G, Well AD, Freedson P, Merriam PA, Reed G, Ma Y, Matthews CE, Hebert JR. Physiological Mechanisms for the Seasonal Changes in Serum Cholesterol Level—Reply. Arch Intern Med. 2004;164(22):2500-2509. doi:10.1001/archinte.164.22.2506-b