SEASONAL-VARIATIONS OF PLASMA-FIBRINOGEN AND FACTOR-VII ACTIVITY IN THE ELDERLY - WINTER INFECTIONS AND DEATH FROM CARDIOVASCULAR-DISEASE

There are approximately 20 000 excess deaths from cardiovascular disea se each winter in England and Wales, The reasons for the excess have n ot been fully elucidated. For one year, we studied 96 men and women ag ed 65-74 living in their own homes in order to examine seasonal variat ion in plasma fibrinogen and factor VII clotting activity (fVIIc), and to investigate relationships with infection and other cardiovascular- disease risk factors. Both fibrinogen and FVIIc plasma values were gre ater in winter with estimated winter-summer differences (confidence in tervals) of 0.13 (0.05-0.20) g/L for fibrinogen and 4.2 (1.2-7.1)% of standard for FVIIc. These differences could account for 15% and 9% inc reases in ischaemic heart disease risk in winter respectively. After a djustment for confounding by season, fibrinogen was strongly related t o neutrophil count (p<0.0001), C-reactive protein (p<0.0001), alpha 1- antichymotrypsin (p<0.0001), and self-reported cough (p<0.0001) and co ryza (p=0.0004), but not to ambient temperature. Therefore, we suggest that seasonal variation in fibrinogen might be induced by winter resp iratory infections via activation of the acute phase response. Seasona l variations in the cardiovascular risk factors fibrinogen and FVIIc p rovide further possible explanations for the marked seasonal variation in death from ischaemic heart disease and stroke in the elderly.