Secular trends in social class differences of height, weight and BMI of boys from two schools in Lisbon, Portugal (1910-2000).

Data on the physical growth of children can provide useful information about the temporal changes in the economic conditions of the society in which they live and the extent of social inequalities within that society as well. Several studies have documented secular changes in the physical growth of children or of adult height, but seldom have the socioeconomic differences in secular trend been reported. The aim of this study is to examine differences in the secular trend of height, weight and BMI of 10-16-year-old boys enrolled in two schools of opposite socioeconomic makeup in Lisbon, Portugal, in the early and late 20th century. The samples from the upper-middle class come from the Colégio Militar, a military boarding school, and the lower-class samples come from the Casa Pia de Lisboa, a residential school for underprivileged boys. While boys from both schools show an approximate increase of 13.6cm in height, 13.5kg in weight and 2.4kg/m(2) in BMI, the Casa Pia students were shorter and lighter than their Colégio Militar counterparts throughout the 90-year period. Social class differences in mean height, weight and BMI tend to be greater in 1910 than in 2000, but results are statistically significant for height alone. When the two periods are taken together, Colégio Militar boys differ from their Casa Pia counterparts by approximately 6.4cm in height, 4.8kg in weight and 0.4kg/m(2) in BMI. Both samples show a considerable increase in height, weight and BMI but class differences in height, weight and BMI decreased slightly if at all, throughout the 90-year period. This suggests that socioeconomic disparities are persistent, having diminished only slightly since the early 20th century.