Growth in Sweden : surveillance of growth patterns and epidemiological monitoring of secular changes in height and weight among children and adolescents

Abstract

This thesis investigates the growth patterns of infants, children and adolescents in all of Sweden and the secular change for height and weight for schoolchildren. This thesis is based on the study of two cohorts: First, schoolchildren born 1973 from age 7 y to 18 y, and second children born in 1981 from birth to age 19 y. Cohort 1973 was all children born on the 15th of any month in 1973, 3 579 boys and girls. Longitudinal data were collected from school health records. Missing cases were 4.5%. Cohort 1981 was all children born on the 15th of any month of 1981, 3 158 boys and girls. Longitudinal data were collected from child health records and school health records. Missing cases were 1.6%.

Longitudinal data for somatic growth, cohort 1973 from 7 y to 18 y (height and weight), cohort 1981 from birth to 19 y (height and weight), from birth to age 48 mo (head circumference) from two nationally representative sample of children in Sweden, collected from child health records and school health records, can be used for epidemiological monitoring of growth with fewer missing individuals and at lower costs compared with other dedicated studies. Data quality is comparable to similar national surveys.

These studies represent, without selection bias, the current growth situation among children and adolescents, enabling both epidemiological comparisons over time and comparisons with other national surveys.

For the first time in Sweden, and without selection bias, means and distribution of head circumference measurements are documented longitudinally for a nationally representative sample of infants.

The time trend analyses revealed: An increased rate for those born in 1981 compared with those born in 1973 of relative weight reduction episodes was found for both boys and girls. The increase for girls were most pronounced, started from a higher rate and was seen in nearly all body weight categories and in all ages. For boys the reductions increased for all body weight categories in the age interval 7 9 y; otherwise the pattern was much more heterogeneous. Body weight and reduction of BMI were highly correlated in both cohorts, as more of the overweight than the thinner children reduced their BMI. For girls the increase in reduction rate between 1981-born and 1973-born was highest among the thinnest individuals.

From age 7 y to 18 y a strong positive secular change for BMI exists in all ages, and the rate of overweight and obesity is increasing for both boys and girls. Furthermore, obesity was growing more severe.