Associations of serum alkaline phosphatase with metabolic syndrome and mortality

Background: Recent data suggest that elevated serum alkaline phosphatase levels are associated with increased mortality, but the mechanisms for this association are unknown. As metabolic syndrome is associated with higher serum alkaline phosphatase levels, we examined the joint association of mortality with metabolic syndrome and serum alkaline phosphatase levels in the US general population. Methods: Retrospective observational study of 15,234 adult participants in the National Health and Nutrition Examination Survey III. Multivariable Cox regression analyses were used to jointly relate mortality risk to serum alkaline phosphatase and indicators of metabolic syndrome. Results: Prevalence of metabolic syndrome was 14% to 41% among patients in lowest and higher quartiles, respectively, for baseline serum alkaline phosphatase. The mortality hazard ratio for each doubling of serum alkaline phosphatase was 1.52 (95% confidence interval [CI], 1.351.72) adjusting only for demographic factors, and 1.37 (95% CI, 1.211.56) adjusting for both demographic and metabolic syndrome factors in the full cohort, and was 1.83 (95% CI, 1.362.46) adjusting for demographic factors in the subgroup without any of the component conditions of metabolic syndrome. Conclusions: In the US general population, higher levels of serum alkaline phosphatase is a predictor of mortality independent of the baseline prevalence of metabolic syndrome. Further studies are warranted to unravel the mechanisms of this association.