Higher Blood Levels of EPA/DHA Associated with Lower Mortality Risk in Older Swedish Population
Marklund, M. et al., Circulation,132: 586-594 , 2015
Dept. of Public Health and Caring Services , Uppsala University, Uppsala, Sweden
Higher intakes of long-chain omega-3 fatty acids as EPA/DHA from fish, fish oil supplements, and foods enriched with omega-3 fatty acids increase blood and tissue levels of EPA/DHA. Since blood levels of EPA/DHA omega-3 are useful biomarkers for omega-3 status in the body, the present study investigated potential relationships between EPA/DHA levels in the circulation and all-cause mortality plus the risk of developing cardiovascular disease. For this purpose, blood samples were taken from 60-year old Swedish men and women and the EPA/DHA and other omega-3 levels (including the short-chain omega-3 as alpha-linolenic acid (LNA)) were determined in the blood serum cholesterol ester via gas-liquid chromatography. During a median follow-up period of 14.5 years, the occurrence of incident cardiovascular disease (CVD) including fatal and non-fatal myocardial infarction, strokes, others were documented as well as all-cause mortality.
Higher blood levels of EPA and DHA were significantly associated with a lower risk of all-cause mortality in the total population and in both genders during the follow-up period. Individuals having the highest levels of EPA and DHA (top 25 % of the population) experienced a 42 % and 40 % lower risk of mortality, respectively, as compared to those in the bottom 25 %. Higher DHA levels in the circulation were associated with a lower risk of incident CVD in the whole population and in women. However, only in women did higher levels of circulating EPA (in the biomarker) correlate with a lower risk of incident CVD. Unexpectedly, there was a trend for higher circulating levels of LNA to be associated with a higher risk of incident LNA in women.
In this large population study, it is noted that the higher levels of circulating EPA/DHA omega-3 fatty acids which correlated with more favourable outcomes in this older population were predominantly of dietary origin and not via supplementation since the use of fish oil supplements was reported as low (only 1 % of the subjects) in both genders. However, it needs to be considered that the blood sampling of the subjects was done during 1997-1999. During the subsequent 14.5 years, it is highly likely that the use of fish oil supplements on a regular basis rose greatly. Recent surveys in sectors of the Swedish population have indicated the use of fish oil supplements to be much higher than that reported by the authors for the 1997-1999 period.