Secular trends in physical growth, biological maturation, and intelligence in children and adolescents born between 1978 and 1993

Front Public Health. 2024 Apr 29:12:1216164. doi: 10.3389/fpubh.2024.1216164. eCollection 2024.

Abstract

Introduction: Human physical growth, biological maturation, and intelligence have been documented as increasing for over 100 years. Comparing the timing of secular trends in these characteristics could provide insight into what underlies them. However, they have not been examined in parallel in the same cohort during different developmental phases. Thus, the aim of this study was to examine secular trends in body height, weight, and head circumference, biological maturation, and intelligence by assessing these traits concurrently at four points during development: the ages of 4, 9, 14, and 18 years.

Methods: Data derived from growth measures, bone age as an indicator of biological maturation, and full-scale intelligence tests were drawn from 236 participants of the Zurich Longitudinal Studies born between 1978 and 1993. In addition, birth weight was analyzed as an indicator of prenatal conditions.

Results: Secular trends for height and weight at 4 years were positive (0.35 SD increase per decade for height and an insignificant 0.27 SD increase per decade for weight) and remained similar at 9 and 14 years (height: 0.46 SD and 0.38 SD increase per decade; weight: 0.51 SD and 0.51 SD increase per decade, respectively) as well as for weight at age 18 years (0.36 SD increase per decade). In contrast, the secular trend in height was no longer evident at age 18 years (0.09 SD increase per decade). Secular trends for biological maturation at 14 years were similar to those of height and weight (0.54 SD increase per decade). At 18 years, the trend was non-significant (0.38 SD increase per decade). For intelligence, a positive secular trend was found at 4 years (0.54 SD increase per decade). In contrast, negative secular trends were observed at 9 years (0.54 SD decrease per decade) and 14 years (0.60 SD decrease per decade). No secular trend was observed at any of the four ages for head circumference (0.01, 0.24, 0.17, and - 0.04 SD increase per decade, respectively) and birth weight (0.01 SD decrease per decade).

Discussion: The different patterns of changes in physical growth, biological maturation, and intelligence between 1978 and 1993 indicate that distinct mechanisms underlie these secular trends.

Keywords: Flynn effect; IQ; birth weight; cognitive functioning; head circumference; height; skeletal maturation; weight.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Birth Weight*
  • Body Height*
  • Body Weight
  • Child
  • Child Development*
  • Child, Preschool
  • Female
  • Humans
  • Intelligence*
  • Longitudinal Studies
  • Male
  • Switzerland

Grants and funding

The ZLS have been or are funded by the Swiss National Science Foundation (32473B_129956 and 32003B-112324), the International Children’s Center in Paris, the Department of Education of the Canton of Zurich, Switzerland, the University of Zurich, Switzerland, the Hermann Klaus-Stiftung, the Hartmann Müller-Stiftung, the Remo Largo Stiftung für Entwicklungspädiatrie, the Foundation for Research in Science and the Humanities at the University of Zurich, the Maiores Stiftung, the Baugarten Stiftung, the Children’s Research Center of the University Children’s Hospital Zurich, the Velux Stiftung, and the Stiftung Für das Kind Giedion Risch.