A cross-sectional population-based study was
carried out in Pelotas, a medium size (320,000
inhabitants) southern Brazilian city. A comparison
between Pelotas (city) and the whole country with
regard to demographic, socioeconomic and healthrelated
variables is presented in Table 1.
A multiple-stage sampling protocol was carried out
to select a representative sample of households in
Pelotas. All 258 urban census tracts in the city were
listed, and 44 were systematically sampled. One block
was randomly selected in each tract; and within this
block, one street corner was also randomly selected.
Thereafter, every fifth household was visited following
a clockwise direction. All individuals aged 40 to 69
years living in the sampled households were invited to
participate in the study. The design effect associated
with the cluster sampling was equal to 1.1 for the three