Time trends in body height according to educational level. A descriptive study from the Tromsø Study 1979-2016

The objective of our study was to describe time trends in body height according to attained educational level in women and men in Norway. We used previously collected data from six repeated cross-sectional studies in the population based Tromsø Study 1979-2016. Measured body height in cm and self-reported educational level were the primary outcome measures. We included 31 466 women and men aged 30-49 years, born between 1930 and 1977. Participants were stratified by 10-year birth cohorts and allocated into four groups based on attained levels of education. Descriptive statistics was used to estimate mean body height and calculate height differences between groups with different educational levels. Mean body height increased by 3.4 cm (95% confidence interval (CI) 3.0, 3.8) in women (162.5-165.9 cm) and men (175.9-179.3 cm) between 1930 and 1977. The height difference between groups with primary education compared to long tertiary education was 5.1 cm (95% CI 3.7, 6.5) in women (161.6-166.7 cm) and 4.3 cm (95% CI 3.3, 5.3) in men (175.0-179.3 cm) born in 1930-39. The height differences between these educational groups were reduced to 3.0 cm (95% CI 1.9, 4.1) in women (163.6-166.6 cm) and 2.0 cm (95% CI 0.9, 3.1) in men (178.3-180.3 cm) born in 1970-77. Body height increased in women and men. Women and men with long tertiary education had the highest mean body height, which remained stable across all birth cohorts. Women and men in the three other groups had a gradual increase in height by birth cohort, reducing overall height differences between educational groups in our study population.