2.1. Stochastic decision model
A stochastic decision model was constructed in Excel to calculate the lifetime costs and outcomes of providing B- vitamin treatment to people over 60 years with high levels of tHcy, which was compared to the lifetime costs and out comes of not providing them with the treatment. The model performed 10,000 iterations of all cost and effect parameters using prespecified distributions of input parameters and recording incremental costs and incremental qualit- adjusted life years (QALYs) from each iteration. Input parameters were related to the target population, treatment ef- fect, costs, and health outcomes (life years and QALYs). The incremental costeffectiveness ratios (ICERs) were expressed as costs per QALY per treated person. The ICERs were plotted on cost-effectiveness planes to display the uncertainty in the results.