Vitamin D is thought to be required for cardiovascular health, with mechanistic studies showing that vitamin D may affect endothelial function, fibrosis and inflammation
Meta-analyses of observational studies have determined that serum vitamin D (25OHD) is inversely related to cardiovascular mortality in healthy individuals, but studies among patients with cardiovascular disease have produced inconsistent results.
To better understand the relationship between serum vitamin D and mortality in patients with stable cardiovascular disease, researchers in Norway evaluated prospective data from 4114 individuals with stable angina pectoris.
Patients were recruited from two university hospitals in Norway between 1999 and 2004, at which point baseline serum 25OHD levels were measured.
Plasma 25OHD ranged from 8.4 to 197 nmol/L (3.2–78.8 ng/mL). Patients were followed until death or 2013, with a 12-year mean duration of follow-up.
Of the 4114 individuals followed, there were 895 (21.8%) deaths from all causes and 407 (9.9%) deaths from cardiovascular disease.
Patients in the upper three quartiles of 25OHD concentration were at significantly lower risk of all-cause and cardiovascular mortality when compared with those in the lowest quartile.
Compared with the lowest quartile of 25OHD concentration, hazards ratios (HRs) for the upper three quartiles for all-cause mortality were 0.64, 0.56 and 0.56, and HRs for cardiovascular mortality were 0.70, 0.60 and 0.57.
The potential thresholds to discriminate between low-risk and high-risk groups were identified as 42.5 nmol/L for all-cause mortality and 40.9 nmol/L (16.4 ng/mL) (for cardiovascular mortality.
Patients with 25OHD >100 nmol/L (40 ng/mL) were also at an increased risk for all-cause mortality.
Vitamin D sufficiency for skeletal health is currently defined as 25OHD >50 nmol/L (20 ng/mL), and the findings from this study suggest that a similar threshold applies to cardiovascular risk.