Effects of vitamin D supplementation on cardiac biomarkers: Results from the STURDY trial.

OBJECTIVES

In observational studies, older adults with low serum vitamin D levels are at higher risk of cardiovascular disease (CVD), but randomized trials have failed to demonstrate reduction in CVD risk from vitamin D supplementation, possibly because the doses of vitamin D supplements tested were too low. Our objective was to determine if higher doses of vitamin D supplementation reduce high-sensitivity cardiac troponin (hs-cTnI) and N-terminal pro-b-type natriuretic peptide (NT-proBNP), markers of subclinical CVD.

METHODS

The Study to Understand Fall Reduction and Vitamin D in You (STURDY) was a double-blind, randomized, response-adaptive trial that tested the effects of 4 doses of vitamin D3 supplementation (200, 1000, 2000, 4000 IU/day) on fall risk among older adults with low serum 25-hydroxyvitamin D concentrations (10-29 ng/mL). Hs-cTnI and NT-proBNP levels were measured at baseline, 3-, 12-, and 24-month follow-up visits. For this ancillary study, we used data from the original trial and compared participants by treatment group: low-dose (200 IU/day) or high-dose (1000+ IU/day). The effects of vitamin D dose on biomarkers were assessed via mixed effects tobit models.

RESULTS

Among 688 participants (mean age of 76.5) hs-cTnI increased in both the low- and high-dose groups by 5.2 % and 7.0 %, respectively; likewise, NT-proBNP increased by 11.3 % and 9.3 %, respectively. Compared to the low-dose, high-dose vitamin D supplementation did not affect hs-cTnI (1.6 %-difference; 95 % CI: -5.3, 8.9) or NT-proBNP (-1.8 %-difference; 95 % CI: -9.3, 6.3).

CONCLUSIONS

Compared to low-dose vitamin D supplementation, doses ≥1,000 IU/ day did not affect markers of subclinical CVD in older adults with low serum vitamin D levels.