Background-High intake of polyunsaturated fatty acids (PUFAs) may reduce the risk of cardiovascular disease (CVD) and mortality. Large, prospective studies including both sexes and circulating PUFAs as dietary biomarkers are needed. We investigated sex-specific associations of the major dietary PUFAs, eicosapentaenoic acid, docohexaenoic acid, linoleic acid, and α-linolenic acid, with incident CVD and all-cause mortality in a population-based cohort. Methods and Results-PUFAs in serum cholesterol esters were measured at baseline in 60-year-old Swedish women (n=2193) and men (n=2039). With the use of national registers, 484 incident CVD events (294 men and 190 women) and 456 all-cause deaths (265 men and 191 women) were identified during follow-up (median, 14.5 years) in individuals without prior CVD at baseline. Associations of PUFAs with CVD and mortality were evaluated with Cox proportional hazard models. In multivariable-adjusted models, 1-SD increases in eicosapentaenoic acid and docohexaenoic acid were associated with lower risk of incident CVD among women (hazard ratio PUFAs seem to have selective roles in the development of CVD, whereas possible influences on non-CVD outcomes are less clear. 9 Dietary intake of EPA, DHA, LA, and, to a lesser extent, ALA is reflected in the FA composition in serum cholesteryl esters (CEs); thus, the proportions of these PUFAs in CEs can be used as biomarkers to assess the intake of the respective PUFA.[10-12 Accordingly, FA composition (especially EPA, DHA, and LA) in CEs correlates well with self-reported FA intake in both Swedish 13 and other cohorts.14 Several prospective cohort and nested case-control studies have used serum CE FAs as a biomarker of dietary fat and investigated possible relationships with risks of all-cause and CVD mortality, 15 fatal coronary heart disease (CHD), 16 and incidences of CHD, 17 heart failure, 18 and stroke. 19,20 Among middle-aged Swedish men, a 1-SD increase (5.2%) in serum CE LA was associated with 13% and 15% lower risk of all-cause and CVD mortality, respectively, whereas no significant associations were observed for serum CE EPA, DHA, or ALA. In addition, a recent meta-analysis suggested that CE LA is associated with a lower risk of fatal CHD, whereas no such associations have been observed for n-3 PUFAs. 16 However, previous studies investigating relationships between serum CE PUFAs and CVD-related outcomes have included predominantly men, although men and women may differ in CVD risks and mortality. 21 Thus, identification of possible sex-specific associations might have been hampered by the limited number of women.Furthermore, recent studies have reported inverse associations of both n-6 and n-3 PUFAs in plasma phospholipid with all-cause and cause-specific mortality and with incident CVD in a US cohort of older men and women. 22,23 This study investigated associations between biomarkers of PUFA intake (EPA, DHA, LA, and ALA) in serum CEs and incident CVD and all-cause mortality in men and women, separately and combined, in a ...