Analysis of vitamin K status, and its correlation with inflammation and cognition, in a well-phenotyped cohort of older Irish people

Historically, vitamin K is known for its role in blood clotting; however in recent years additional functions have been identified including a role in sphingolipid metabolism and as an anti-inflammatory agent. Studies have shown correlations between low vitamin K status and poor cognitive function while several biomarkers of inflammation are inversely correlated with cognition. The ELDERMET cohort, a group of well characterised subjects aged ≥ 64 years, were used in this study. The aim of this study was to identify potential associations between vitamin K status and cognition as well as any correlations between biomarkers of inflammation and cognition using a subgroup of the ELDERMET cohort. In addition the study aimed to ascertain significant differences in variables across living stratification i.e. the community dwelling subjects versus those in long term care. Subjects were divided into 4 groups based on their Mini Mental State Exam (MMSE) score. Vitamin K status was determined by measuring dietary and serum phylloquinone (vitamin K) status. Percent undercarboxylated osteocalcin (% ucOC) was also measured in serum as a long-term indicator of functional vitamin K status. Biomarkers of inflammation including high sensitivity C-reactive protein (hsCRP), Interleukin 6 (IL-6), Interleukin 8 (IL-8) and Tumour Necrosis Factor alpha (TNFα) were measured. Analysis of variance (ANOVA) revealed significant differences between markers of vitamin K status and inflammation and MMSE categories. Positive correlations were found between MMSE and serum and dietary phylloquinone. Inverse correlations were found between MMSE and other variables including %ucOC, hsCRP, IL-6, IL-8 and TNFα. Similarly, significant differences were found across living stratification for biomarkers of inflammation. Analysis of covariance (ANCOVA) showed a significant difference in dietary phylloquinone intake between those with severe cognitive impairment and those with normal cognitive function, and between those with moderate cognitive impairment and normal functionality. In addition, a significant difference between IL-6, TNFα and hsCRP was found especially between those with poor cognitive function and those with normal cognitive ability. This study adds to the growing body of evidence which suggests a role for vitamin K in cognitive function. Findings from this study have the potential to help inform public health policy and dietary recommendations aimed at promoting healthy aging.