Lipoprotein-associated phospholipase A2, hormone use, and the risk of ischemic stroke in postmenopausal women

Few studies have investigated the role of elevated lipoprotein-associated phospholipase A2 (Lp-PLA2) with stroke risk, and those that have are based on small numbers of strokes. No study has evaluated the effect of hormone therapy use on the association of Lp-PLA2 and stroke. We assessed the relationship between Lp-PLA2 and the risk of incident ischemic stroke in 929 stroke patients and 935 control subjects in the Hormones and Biomarkers Predicting Stroke Study, a nested case-control study from the Women's Health Initiative Observational Study. Mean (SD) levels of Lp-PLA2 were significantly higher among case subjects (309.0 [97.1]) than control subjects (296.3 [87.3]; P<0.01). Odds ratio for ischemic stroke for the highest quartile of Lp-PLA2, compared with lowest, controlling for multiple covariates, was 1.08 (95% CI: 0.75 to 1.55). However, among 1137 nonusers of hormone therapy at baseline, the corresponding odds ratio was 1.55 (95% CI: 1.05 to 2.28),whereas there was no significant association among 737 hormone users (odds ratio: 0.70; 95% CI: 0.42 to 1.17; P for interaction=0.055). Moreover, among nonhormone users, women with high C-reactive protein and high Lp-PLA2 had more than twice the risk of stroke (odds ratio: 2.26; 95% CI: 1.55 to 3.35) compared with women low levels in both biomarkers. Furthermore, different stroke cases were identified as high risk by Lp-PLA2 rather than by C-reactive protein. Lp-PLA2 was associated with incident ischemic stroke independently of C-reactive protein and traditional cardiovascular risk factors among nonusers of hormone therapy with highest risk in those who had both high C-reactive protein and high Lp-PLA2.