Clinical outcome measures

For the cost-utility analysis, the EuroQol-5D with three levels for each of the five health dimensions (EQ-5D-3L) was used to assess quality of life at baseline, and at 6, 12 and 24 month follow-up [10]. Health utilities were estimated with the Dutch tariff [11]. QALYs were calculated by multiplying the utilities with the amount of time a participant spent in a particular health state. Transitions between health states were linearly interpolated.

Outcome measures of the cost-effectiveness analyses were the estimated risk of developing T2DM and the estimated risk of CVD mortality. The 9-year risk of developing T2DM was estimated with the risk formula derived from the Atherosclerosis Risk In Communities (ARIC) Study, based on ethnicity, parental history of diabetes, systolic blood pressure, waist circumference, and height [12]. This formula was selected because of its potential applicability in primary care, since it includes only non-invasive methods to assess participants’ T2DM risk. The 10-year risk of CVD mortality was estimated with the formula developed by the Systematic COronary Risk Evaluation (SCORE) project [9] which includes sex, smoking status, total cholesterol, and systolic blood pressure. The application of the SCORE formula was considered to be the most useful for the calculation of CVD mortality risk. Former comparative analyses of the SCORE, the Framingham and the UKPDS formulae demonstrated that the Framingham function may overestimate an individual’s absolute chronic heart disease risk, and the UKPDS formula was not chosen based on its specific inclusion of T2DM as variable [13]. Baseline risks and follow-up risks were estimated while standardizing the age of each participant at 60 years. The formulas and the estimated risks are further explained in Additional file 1. Data was collected by means of physical measurements and questionnaires. A detailed description of the data collection has previously been published [5].