Vitamin D insufficiency may be associated with increased risk of coronary heart disease (CHD) and cardiovascular disease (CVD) in general, but uncertainties exist beyond published reports. The Vitamin D Studies Collaboration (VitDSC) is a CEU-led consortium that is assessing in detail the associations of 25-hydroxyvitamin D [25(OH)D], the principal clinical biomarker of vitamin D status, with cardiovascular disease outcomes and cause-specific mortality by meta-analysis of individual participant data (IPD) from 106,900 participants in 34 prospective cohort studies. The specific aims are:

1. To assess correlates of 25(OH)D levels and the shape of dose-response relationships between 25(OH)D and cardiovascular disease outcomes and cause-specific mortality.
2. To consistently adjust for confounding factors (e.g. season, age, sex, obesity, smoking, ethnicity, physical activity, etc) in assessing the above associations.
3. To correct associations for impact of regression dilution in both 25(OH)D levels and in the confounders.
4. To evaluate whether the association of 25(OH)D and outcomes importantly differ by clinically relevant subgroups (e.g. age, sex, smoking, diabetes, obesity, ethnicity, and other established risk factors) and methods of assessment.
5. To assess the incremental predictive value of 25(OH)D for cardiovascular disease risk prediction beyond conventional CVD risk factors.
6. To assess the causal relevance of 25(OH)D in cardiovascular disease and other major disease outcomes using Mendelian randomisation.