Surveillance System for Risk and Protective Factors for Chonic Diseases by Telephone Survey (Vigitel): changes in weighting methodology

Objective: to introduce the methodology used to calculate post-stratification weights of the 2012 Surveillance System for Risk and Protective Factors for Chronic Diseases by Telephone Survey (Vigitel) and to compare the trends of indicators estimated by cell-by-cell weighting and raking methods. Methods: in this panel of cross-sectional studies, the prevalences of smokers, overweight, and intake of fruits and vegetables from 2006 to 2012 were estimated using the cell-by-cell weighting and raking methods. Results: there were no differences in time trends of the indicators estimated by both methods, but the prevalence of smokers estimated by the raking method was lower than the estimated by cell-by-cell weighting, whilst the prevalence of fruit and vegetable intake was higher; for overweight, there was no difference between the methods. Conclusion: raking method presented higher accuracy of the estimates when compared to cell-by-cell weighting method, proving to be most convenient, although it presents register coverage bias.