Sex differences in secular changes in height and weight among affluent Portuguese boys and girls from 1913 to 2012

Secular changes in the physical growth of children in the 20th century have been examined largely between cohorts of boys or men, with fewer studies examining changes among girls/women or both sexes. Sex-specific growth trajectories and differential cultural treatment of the sexes can affect how girls and boys respond to changes in the ontogenetic environment. This study examined secular change in height (cm) and weight (kg) in affluent Portuguese school children from three periods over the 20th century: an early (1913–1916), middle (1929–1943), and late (1992–2012) period. Anthropometric data was taken from medical records and archives of two boarding schools located in or near Lisbon: the Colégio Militar for boys and the Instituto de Odivelas for girls. Height and weight data were collated from over 1349 children (over 825 boys and 524 girls), aged to 10 to 17 years. Height and weight were plotted against age for the three periods to assess secular changes and sex differences in the secular trend. Results indicate a similar pattern of secular change across boys and girls, wherein children measured in the late period demonstrated an increase in height and weight, with the greatest increase occurring between the middle and late periods. The increase in height and weight can be attributed to changes to the socioeconomic environment in Portugal after the 1960s, but particularly after the democratic transition of 1974. This includes population-wide improvements in living standards, sanitation, decreased disease load, access to medical care and improved quantity and quality of nutrition. Cultural-based preferential treatment of boys may have taken place, as boys increased more in relative and absolute height and weight.