Abstract

The aim of this study was to evaluate differences in the socio-demographic and health characteristics among adults (18 years or older) with and without a residential telephone line, using data from the Campinas Health Survey (ISACamp), Brazil, a population-based cross-sectional study carried out in 2008 and 2009. Descriptive statistics and χ² tests were calculated for these variables. It also estimated the bias associated with non-coverage of the population without telephones before and after the use of post-stratification adjustments. The bias impact on the CIs of these estimates was assessed in terms of accuracy achieved. Approximately 76% of respondents owned a residential telephone line in Campinas. It was possible to identify differences in socio-demographic data for the population according to the ownership of telephone line, except for marital status. The analysed data also showed that people with telephone had higher prevalence of self-reported osteoporosis, drug use in the 3 days prior to the interview, dental visits in the last 12 months, mammography in women 40 years or more and affiliation to medical plan of health, compared to respondents without a telephone. After the post-stratification adjustment, there were reductions in the bias of estimates for those variables associated with the ownership of telephone line. In this study, except for osteoporosis, post-stratification adjustment was insufficient to correct the bias of non-coverage. Studies with samples where not all units in the target population are likely to be selected as the telephone interview, should consider the potential biases embedded in each variable.