Design of a population-based study of cardiovascular risk in Castile and Leon [Spain] through primary care teams

We describe the design and the response indicators in a cross sectional study to estimate several factors associated with cardiovascular risk in the population of Castile and Leon. A sample of 4,950 individuals aged 15 years and above was obtained in two stages: in the first stage, 198 primary care physicians were selected and in the second stage a sample of 25 persons from each primary care physician's list was obtained. The response rate was 98% among primary care physicians and 80% among the population. Statistically significant differences were found in age distribution between the frame sample and the definitive sample. After applying design adjustments, only the group aged 35-64 years was significantly overdimensioned. Access to the general population in primary health care is a feasible and effective procedure. A high response rate contributes to the validity of the information.