Plasma fibrinogen and its correlates in Japanese and US population samples

In a preliminary 1987 study, we reported that the plasma fibrinogen level was significantly higher in Caucasian American men than Japanese men. To confirm this finding, we used data from 1,020 Japanese men and women in a 1989-1991 Akita, Japan, population study and from >15,000 men and women from the 1986-1989 Atherosclerosis Risk in Communities (ARIC) Study. To examine further the correlates of plasma fibrinogen level, subsamples of nonsmoking Akita Japanese (n=150) and Minneapolis Caucasians (n=150) were also studied separately in 1990. Compared with the Japanese in the Akita study, Caucasians and African Americans in ARIC had a 23-40 mg/dL higher age-adjusted fibrinogen level for men and a 25-67 mg/dL higher level for women. In the subsample, the mean plasma fibrinogen value was 288 mg/dL in Caucasian men and 248 mg/dL in Japanese men (test for difference: p<0.001). Women showed a similar racial difference: 300 mg/dL in Caucasians and 257 mg/dL in Japanese (p<0.001). There were weak but positive correlations of plasma fibrinogen with age and body mass index and weak inverse correlations with alcohol intake, high density lipoprotein cholesterol, and triglycerides in most of the sex-race groups. For women, plasma fibrinogen was positively associated with menopause and inversely associated with the use of hormone replacement therapy. Total fish intake was inversely associated with plasma fibrinogen in all sex-race groups, and the association was statistically significant for Caucasian men. After controlling for these correlates, the Japanese-Caucasian difference in mean fibrinogen value was smaller but was not eliminated: mean difference of 23 mg/dL (95% confidence interval, 0-47) for men and of 41 mg/dL (16-67) for women. These results confirm and extend the preliminary finding that plasma fibrinogen level is higher in American than in Japanese populations. This may contribute to the higher rate of coronary heart disease mortality in the United States than Japan.