Trends in weights, heights, BMI and comparison of their differences in urban and rural areas for Iranian children and adolescents 2-18-year-old between 1990-1991 and 1999
Background Secular trends in height and weight are interesting because in middle- and low-income countries they are a marker for changes in population health. The present study aims to evaluate the secular trend in height and weight and body mass index (BMI) of Iranian children and adolescents aged 2-18 years old between 1990-1991 and 1999 and compare the magnitude of urban-rural differences during this period for the first time in an Asian country. Methods Data from two national health surveys in 1990-1991 and 1999, of 22 349 and 25 196 weight and height measures of Iranian children and adolescents were used to study the trend and compare its difference in urban and rural children. Logarithmic transformation of weight, height and BMI was modelled as a polynomial in age for urban and rural boys and girls in each survey separately. The trend in urban and rural growth indexes (weight, height and BMI) and also the comparisons of urban-rural differences between two national surveys were tested in logarithmic scale using a weighted form of Z statistic for comparison of two means adjusted for age groups. Results Urban and rural boys and girls became taller and heavier (P < 0.02) with no change of BMI (P > 0.05) during the period. There was not any significant difference between the magnitudes of urban-rural difference between two surveys (P >= 0.61). Conclusion Although generally positive weight and height trend was observed among urban and rural residents, the magnitude of their differences was not changed.