Significant inverse association of marine n-3 fatty acids with plasma fibrinogen levels in Japanese in Japan but not in whites or Japanese Americans

Background Numerous studies reported beneficial effects of marine n-3 fatty acids (n-3 FAs) on cardiovascular disease (CVD) and its risk factors. However, the association of marine n-3 FAs with plasma fibrinogen, a risk factor for CVD, remains uncertain. Methods In a population-based, cross-sectional study of 795 men aged 40-49 without CVD (262 whites in Allegheny County, Pennsylvania, US, 302 Japanese in Kusatsu, Japan, and 229 Japanese Americans in Honolulu, Hawaii, US), we examined the association of marine n-3 FAs with plasma fibrinogen. Serum FAs were measured by capillary gas-liquid chromatography. Marine n-3 FAs were defined as the sum of docosahexaenoic, eicosapentaenoic, and docosapentaenoic acids. Plasma fibrinogen was measured by an automated clot-rate assay. Multiple linear regression analyses were performed to assess the association. Results White, Japanese, and Japanese American men had mean marine n-3 FAs levels of 3.47%, 8.78%, and 4.46%, respectively. Japanese men had a significant inverse association of marine n-3 FAs with fibrinogen (standardized regression coefficient of -0.11, p=0.049), after adjusting for age, body-mass index, and current smoking. The significant inverse association remained after further adjusting for diabetes, C-reactive protein, triglycerides and other variables. White or Japanese American men did not show a significant association. Conclusion We observed the significant inverse association of marine n-3 FAs with fibrinogen in Japanese, but not in whites or Japanese Americans. The observation suggests that marine n-3 FAs at very high levels, as seen in the Japanese, may decrease plasma fibrinogen levels.