The threshold phenomenon we observed for changes in HRs with increasing EPA concentrations agreed with several other prospective observational studies and clinical trials (42), indi- cating that most or all beneficial effects of long-chain n
3 fatty acids are not linear. In populations in whom the majority already has a nutritional intake or cell concentration of long-chain n
3 fatty acids above the thresholds for protection, a further increase intheintakecannotbeexpectedtoprovideanyadditionalclinical effect. The Norwegian population, especially the elderly, tradi- tionally has a high intake of fish. This is a characteristic we share with other populations throughout the circumpolar north, where fish is abundant and is an important part of the diet. Most of our patients, therefore, already have a dietary intake sufficient to achieve the protection offered by these oils. Our low EPA group has a mean % by wt of EPA and DHA of 1.01 and 7.09, respectively. The corresponding values found by Harris et al (43) were 0.55 and 3.02. Crowe et al (44) and Welch etal(45)reportedEPAconcentrationsof1.02and1.26mol%and DHA concentrations of 2.64 and 5.2 mol%, respectively. The corresponding values in our low-EPA group are 0.96 and 6.17 mol%. Data from the study by Harris et al (43) and Crowe et al (45) were recalculated by combining their subpopulation data to reflect their total study population. This suggests that the lowest FIGURE 2. Hazard ratios (HRs) for all-cause death given as a function of EPA concentrations at inclusion. The model was controlled for age, sex, assignment to GEMU treatment, Barthel Index, residence (private home or sheltered housing), current smoking status, history of cardiovascular disease, HDL cholesterol, LDL cholesterol, prealbumin, and
-tocopherol. The first- quartile HR was defined as 1.0 and used as referent, the second-quartile HR was 0.53 (95% CI: 0.33, 0.86), the third quartile HR was 0.48 (95% CI: 0.29, 0.79),andthefourthquartileHRwas0.57(95%CI:0.34,0.96).Patientswere categorized in quartiles according to EPA concentration, as described in Figure 1, and HRs of all-cause death among EPA groups were calculated using multivariate Cox analysis. n
3 FATTY ACIDS AND MORTALITY IN ELDERLY PATIENTS 727 Downloaded from https://academic.oup.com/ajcn/article-abstract/88/3/722/4649085 by guest on 19 April 2018 quartileinourpopulationisinthesamerangeasthemeanofother populations. Comparison of different studies, however, is diffi- cult because of the lack of standardized methods and available calibrators. We report a DHA-EPA ratio of 7.0, whereas the corresponding ratios found by Harris et al (43), Crowe et al (44), andWelchetal(45)are5.5,2.6,and4.1,respectively,suggesting either population differences in the intake and metabolism of EPA and DHA or difference in analytic methods. To facilitate study comparison, we analyzed 23 fatty acids in a commercially available calibrator ( see Supplemental Table 1 under “Supple- mental data” in the online issue). Although the present study did not adjust for all known con- founders, the results suggest that a moderate dietary intake of n
3 fatty acids in the elderly (age
65 y) reduces their overall mortality if they become acutely ill and hospitalized. The results alsosuggestthat 25%ofthisNorwegianpopulationmighthave benefited from an increased dietary intake before the acute inci- dent. The reported differences in EPA and DHA concentrations (43–45) suggest that this proportion might be considerably higher in other populations. In future intervention studies, base- line status of marine n
3 fatty acids should be established in eligible study participants and entered in the inclusion criteria to include only participants who are likely to benefit from interve
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