Does liver damage explain the inverse association between vitamin D status and mortality?

Several observational studies have linked vitamin D deficiency with an increased risk of all cause mortality. Vitamin D deficiency is common among patients with liver diseases. In a random sample of the general population, we investigated whether the inverse association between vitamin D status and all-cause mortality could be explained by liver damage as reflected by increased levels of liver enzymes.

We included a total of 2649 persons examined in 1993e1994. Vitamin D status was assessed as serum 25-hydroxyvitamin D and liver enzyme levels were measured. Information on all-cause mortality was obtained from the Danish Central Personal Register until July 2011. Median follow-up time was 17.0 years, and there were 736 deaths.

Multivariable Cox regression analyses with age as underlying time axis and delayed entry showed lower mortality risk with higher vitamin D levels and this was essentially unaffected by adjustment for liver enzyme levels with hazard ratio, 0.96 (95% confidence interval, 0.93e0.99) for a 10 nmol/L higher vitamin D level.

The present study did not support our hypothesis that the well-known association between low vitamin D status and mortality is explained by liver damage as reflected by levels of liver enzymes.