1. In 2019, a mean height difference of 20 cm or greater was estimated between adolescents in countries with the tallest populations such as the Netherlands, Estonia, Montenegro and those with the shortest populations such as Timor-Leste, Bangladesh and Nepal.
2. The healthiest changes, considering both height and BMI (greater gains in height relative to BMI) over the last 35-years, occurred in girls in South Korea, Vietnam and some central Asian countries and boys in central and Western Europe. The unhealthiest changes (greater gains in weight relative to height) occurred in sub-Saharan Africa, New Zealand and the USA for boys and girls.
Evidence Rating Level: 2 (Good)
Study Rundown: Height and body-mass index (BMI) serve as proxy measures of the quality of nutrition and living environment during early life, childhood, and adolescence. Having low height and excessively low BMI are both measures associated with increased morbidity and mortality. In contrast, high BMI is associated with increased risk of disability and premature death in adulthood. To date, much of the current research on global health and nutrition has focused on the period from preconception to 5 years of age with few studies investigating global trends in BMI or height for school-aged children (5-19 years). This population-based study pooled data from 2181 individual studies measuring height and weight in 65 million participants across 200 countries and territories over a 35-year period. Results showed highly variable age trajectories and trends over time in height and BMI of school-aged children across countries. Overall, the unhealthiest changes including gaining too little height, increased weight for height or both-occurred primarily in the USA, countries in sub-Saharan Africa, and New Zealand for boys and girls. The healthiest changes occurred in girls from South Korea, Vietnam, Saudi Arabia, Turkey and some central Asian countries and in boys from Central and Western Europe. Key strengths of the study include the notably large scale including 193 countries and territories while still maintaining a high standard of data representativeness and quality. However, although potential driving factors such as genetics, nutrition, and physical activity were proposed, the present study lacked the required data to correlate these characteristics with the observed trends and trajectories of height and BMI.
In-Depth [retrospective cohort]: This population-based study utilized a database of cardiometabolic risk factors collected by the Non-communicable Disease Risk Factor Collaboration (NCD-RisC) for analysis of BMI and height in school-aged children and adolescents (5-19 years) between 1985 and 2019. A total of 65 million participants across 2181 population-based studies with measurements of height and weight were included. These studies were conducted across 200 countries and territories. Primary outcomes included population mean height and mean BMI from ages 5 to 19.
In 2019, the 19-year-olds who were on average the tallest in the world were from Northwestern and central European countries including the Netherlands (mean height 183.8 cm, 95% credible interval (CrI) 181.5 to 186.2) followed by Montenegro, Estonia, and Bosnia and Herzegovina for boys; and the Netherlands (mean height 170.4 cm, 95% CrI 168.3 to 172.4), Montenegro, Denmark and Iceland for girls. The 19-year-olds who were the shortest, on average, lived in south and southeastern Asia, Latin America and east Africa (mean height 160.1 cm, 95% CrI 158.0 to 162.2) for boys and Guatemala (150.9 cm, 95% CrI 149.4 to 152.4), Bangladesh, Nepal and Timor-Leste for girls. The 20 cm or higher difference in height between the tallest and shortest mean height countries represents approximately 6 years of growth gap for boys and 8 years for girls. When considering changes in both BMI and height over the last 35-years, girls in South Korea, Vietnam, Saudi Arabia, Turkey and some central Asian countries and boys in Central and Western Europe (Portugal, Denmark, Poland, Montenegro) had the healthiest anthropometric changes (greater increases in height relative to BMI). In contrast, the unhealthiest changes (greater increases in weight relative to height) occurred in Sub-Saharan Africa, New Zealand and the USA for both boys and girls.
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