Circulating vitamin K is inversely associated with incident cardiovascular disease risk among those treated for hypertension in the health, aging, and body composition study (Health ABC)

Background: A role for vitamin K in coronary artery calcification (CAC), a subclinical manifestation of cardiovascular disease (CVD), has been proposed because vitamin K-dependent proteins, including the calcification inhibitor matrix Gla protein (MGP), are present in vascular tissue. Observational studies found that low circulating phylloquinone (vitamin K-1) was associated with increased CAC progression, especially in persons treated for hypertension. It is unknown whether hypertension treatment modifies this putative role of vitamin K in clinical CVD risk. Objective: We determined the association between vitamin K status and incident clinical CVD in older adults in the Health ABC (Health, Aging, and Body Composition Study) and whether the association differed by hypertension treatment status. Methods: Plasma phylloquinone was measured in 1061 participants free of CVD (70-79 y of age, 58% women, 39% black). Plasma uncarboxylated MGP [(dp)ucMGP] was measured in a subset of 635 participants. Multivariate Cox models estimated the HR for incident CVD over 12.1 follow-up years. Effect modification by hypertension was tested with the use of interaction terms. Results: Neither low plasma phylloquinone (≤ 0.2 nmol/L) nor elevated (dp)ucMGP (≥574 pmol/L) was significantly associated with incident CVD [respective HRs (95% CIs): 1.27 (0.75, 2.13) and 1.02 (0.72, 1.45)]. In participants treated for hypertension (n = 489; 135 events), low plasma phylloquinone was associated with higher CVD risk overall (HR: 2.94; 95% CI: 1.41, 6.13). In those with untreated hypertension (n = 153; 48 events) and without hypertension (n = 418; 92 events), low plasma phylloquinone was not associated with incident CVD. The association between high (dp)ucMGP did not differ by hypertension treatment status (P-interaction = 0.72). Conclusions: Vitamin K status was not significantly associated with CVD risk overall, but low plasma phylloquinone was associated with a higher CVD risk in older adults treated for hypertension. Additional evidence from larger clinical studies is needed to clarify the importance of vitamin K to CVD in persons treated for hypertension, a segment of the population at high risk of clinical CVD events.