Effect of the inclusion of mobile phone interviews to Vigitel

OBJECTIVE: To evaluate the impact on the prevalence changes of risk factors for chronic diseases, published in the Surveillance System of Risk and Protection Factors for Chronic Diseases by Telephone Survey (Vigitel), after the inclusion of data from the population only with mobile phone. METHODS: Our study used data from the 26 State capitals and Federal District of Brazil obtained by the National Survey on Health (PNS) and Vigitel, both held in 2013. In each capital, we added a subsample of 200 adults living in households with only mobile phones, extracted from PNS, to the Vigitel 2013 database, with approximately 1,900 households, named Vigitel dual frame. RESULTS: Vigitel results showed absolute relative biases between 0.18% and 14.85%. The system underestimated the frequency of adult smokers (10.77%), whole milk consumption (52.82%), and soft drink consumption (22.22%). Additionally, it overestimated the prevalence of hypertension (25.46%). In the simulations using Vigitel dual frame, with inclusion of the sample of adults living in households with only mobile phones, the bias of estimates was reduced in five out of eight analyzed indicators, with greater effects in regions with lower rates of landline coverage. In comparing regions, we observed negative correlation (ρ = −0.91) between the percentage of indicators with presence of bias and the percentage of households with only mobile phone. CONCLUSIONS: The results of this study indicate the benefits of including a subsample of 200 adults with only mobile phone on the Vigitel sample, especially in the capitals of the North and Northeast regions.