Vitamin K intake and mortality in people with chronic kidney disease from NHANES III

Abstract

Cardiovascular disease (CVD) is the leading cause of death in patients with chronic kidney disease (CKD), partly due to increased vascular calcification. Vitamin K plays a role in preventing vascular calcification in CKD yet the relationship between vitamin K intake and mortality in CKD patients remains unclear. This observational cohort study included 3401 participants with CKD from the Third National Health and Nutrition Examination Survey. Vitamin K intake was estimated from 24-h dietary recalls (1988-94). Mortality was determined from the National Death Index records through 2006. Cox-proportional hazards regression was used to estimate Hazard Ratios (HR) by comparing those with adequate intake of vitamin K to those with low intake, adjusting for advanced CKD covariates. For sensitivity analysis, these associations were also examined among those with different renal status. During a median follow-up of 13.3 years (37,408 person-years), 1815 and 876 participants died from all-cause and CVD causes, respectively. 72% of the participants had vitamin K intake lower than the recommended adequate intake. Participants with vitamin K intake higher than recommended adequate intake for vitamin K were associated with lower risk of all-cause (HR = 0.85; 95%: 0.72-1; P = 0.047) and CVD mortality (HR = 0.78; 95%: 0.64-95; P = 0.016). Sensitivity analyses in subgroups with advanced CKD revealed similar findings. This observational study suggests that adequate intake of vitamin K may be associated with reduced all-cause and CVD mortality in CKD patients. However, vitamin K may be a marker of a healthy diet; therefore clinical trials may help in clarifying the effect of vitamin K independent of a healthy diet.