[Surveillance of risk factors for chronic diseases through telephone interviews]

To describe methods and initial findings of a surveillance system of risk factors for chronic non-communicable diseases (CNCDs) based on telephone interviews.

Interviews undertaken in a random sample of the adult population of the Municipality of Sao Paulo living in households with telephone. Sampling was done in two steps and included the random selection of households and the random selection of the household member to be interviewed. The system's questionnaire investigated demographic and socioeconomic characteristics, food consumption and physical activity patterns, smoking, consumption of alcoholic beverages, recalled weight and height and reported medical diagnoses of hypertension and diabetes, among other topics. Prevalence estimates of selected risk factors for CNCDs were calculated for the adult population with telephone and for the city's entire adult population. In this last case, we applied sample weighting factors that took into account demographic and socioeconomic differences between the adult population with telephone and the entire adult population of the municipality.

Strong differences between sexes were found for most risk factors: low consumption of fruit and vegetables, high consumption of alcohol and overweight were more frequent among men while sedentary lifestyle and hypertension were more frequent among women. Additional possibilities of stratification of risk factor prevalences allowed by the surveillance system are illustrated using age groups, schooling, and place of residence in the city.

System performance was considered as good and was better than the performance observed in similar systems operating in developed countries when evaluated with basis on the representativeness and reliability of the estimates and on costs. The cost per concluded interview was eight times lower than the cost usually seen in similar systems in developed countries and four to eight times lower than the cost of traditional household surveys undertaken in the city of Sao Paulo.