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Age–period–cohort analysis of trends in blood pressure and body mass index in children and adolescents in Hong Kong
  1. Man Ki Kwok1,
  2. Yu Kang Tu2,
  3. Ichiro Kawachi3,
  4. C Mary Schooling1,4
  1. 1 School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, Hong Kong, China
  2. 2 Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan
  3. 3 Department of Social and Behavioral Sciences, Harvard T. H. Chan School of Public Health, Boston, Massachusetts, USA
  4. 4 CUNY Graduate School of Public Health and Health Policy, City University of New York, New York, New York, USA
  1. Correspondence to Dr C Mary Schooling, School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China; cms1{at}


Background The declining or fluctuating trend in blood pressure (BP) despite the rising trend in body mass index (BMI) during childhood and adolescence is unexplained. We decomposed trends in BP and BMI to identify the relevance of early-life and contemporaneous factors.

Methods We assessed the relative contribution of age, period and cohort to secular trends in BP in children and adolescents (9–18 years) from 1999 to 2014 and BMI (6–18 years) from 1996 to 2014 in Hong Kong, China.

Results After accounting for age, period effects contributed more than cohort effects to the overall fluctuating BP trend and the rising BMI trend observed in this Chinese population. For both sexes, BP fell from the start of period to a low point in 2003–2005 but then rose. BMI rose strongly across the period before levelling off in 2009–2010. Earlier cohorts (born in 1983–1984) had higher BP and BMI than later cohorts.

Conclusion With globalisation and associated lifestyle changes, successive generations of children and adolescents in a recently developed Chinese setting had lower BP and BMI, but this fall was offset until recently by population-wide increase in BMI. School-based health promotion efforts could have partly mitigated the population-wide rise in child and adolescent BMI, while socioeconomic transition or other factors could be relevant to changes in BP between generations. Explaining these trends will help identify early-life factors that may contribute to a healthier start as well as contemporaneous factors that may protect against rising trends in adiposity.

  • child health
  • blood pressure
  • obesity
  • age-period-cohort

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  • Contributors MKK conceptualised ideas, designed analytic strategy, performed the literature review, conducted data analysis, interpreted findings and drafted the manuscript. YKT directed analytic strategy, interpreted findings and critically reviewed the manuscript. IK interpreted findings and critically reviewed the manuscript. CMS conceptualised ideas, directed analytic strategy, interpreted findings, revised drafts of the manuscript critically and supervised the study from conception to completion. All authors have read and approved the submission of the manuscript and agreed to be accountable for all aspects of the manuscript in ensuring its accuracy and integrity.

  • Funding This project was supported by the Health and Medical Research Fund (HMRF Grant No. 11121371), Government of the Hong Kong SAR.

  • Competing interests None declared.

  • Patient consent Guardian consent obtained.

  • Ethics approval The University of Hong Kong-Hospital Authority Hong Kong West Cluster Joint Institutional Review Board.

  • Provenance and peer review Not commissioned; externally peer reviewed.