Lower levels of vitamin D, higher rates of death Association of Serum 25-Hydroxyvitamin D Concentrations With All-Cause and Cause-Specific Mortality Among Adult Patients With Existing Cardiovascular Disease https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8496747/ Observational study, non-interventional Background Vitamin D, lower levels, common in patients with…