Lipoprotein-associated phospholipase A₂ and risk of venous thrombosis in older adults

Lipoprotein-associated phospholipase A₂ (Lp-PLA₂) is an enzyme involved in inflammation and platelet function. Inherited deficiency and elevated levels are associated with atherosclerosis. Given potential common etiologies of atherosclerosis and venous thrombosis (VT), we hypothesized that low and high Lp-PLA₂ would be associated with VT risk. Lp-PLA ₂ mass and activity were measured in baseline samples of Cardiovascular Health Study participants (5,888 men and women age ≥65), excluding 354 reporting pre-baseline VT. The study endpoint was VT unrelated to cancer after 11.6 years follow-up. Hazard ratios were estimated using Cox proportional hazard models, adjusting for age, race, sex, and body-mass index. With 129 cases of VT, there was no association of Lp-PLA₂ activity with risk. Adjusted hazard ratios were 1.19 (CI 0.62, 2.29) and 0.87 (CI 0.43, 1.76) for the lowest and highest decile, respectively, compared to the 10-25th percentile. Corresponding hazard ratios for Lp-PLA₂ mass were 1.63 (CI 0.79, 3.34) and 1.33 (CI 0.61, 2.87). Results were robust to several definitions of low or high Lp-PLA₂. While the association of Lp-PLA₂ levels with arterial disease events implies a role for this enzyme in atherogenesis, our findings suggest that it is not prothrombotic.