The primary outcome will be the proportion of patients with any cardiovascular event, evaluated using systematic journal audits. Logistic regression models will be applied to test the hypothesis that there are more cardiovascular events in patients enrolled with a low level of vitamin D (< 50 nmol/l). Secondarily, Cox regression models, based on survival analysis, will be applied, to determine the extent to which independent variables (including different levels of vitamin D at baseline) predict not only whether a cardiovascular event occur, but also when it will occur.