A new study highlights dramatic height increases among Iranian and South Korean men and women over the past century, driven by improved living conditions, but reveals persistent inequalities in parts of Africa and South Asia where progress has stalled or reversed.
Over the past century, Iranian men recorded the largest increase in average adult height of any male population studied, rising by 16.5 cm between birth cohorts born in 1896 and 1996, according to research published in eLife and reported by Reuters. The same analysis, led by the NCD Risk Factor Collaboration with researchers at Imperial College London and the World Health Organisation, examined 1,472 population-based studies covering more than 18.6 million people across 200 countries.
The findings point to a dramatic shift in living conditions rather than any biological change. Imperial College London said the pattern is consistent with better childhood nutrition and healthier environments, while the study authors argued that genetics cannot explain such a rapid rise over such a short period. South Korean women showed the biggest gain among women, increasing by 20.2 cm across the century, while Dutch men were the tallest in the late 20th century at more than 182.5 cm on average.
But the global picture was far from uniform. Reuters reported that several countries in sub-Saharan Africa and parts of South Asia saw little progress, and in some places average adult height stalled or even declined for younger cohorts. The study found that in countries including Niger, Rwanda, Sierra Leone and Uganda, some later generations ended up shorter than those born decades earlier, underscoring how uneven improvements in health and nutrition have been.
Researchers and Imperial College London framed height as a rough measure of childhood conditions, not a direct scorecard of individual health. Better access to nutritious food, cleaner water, healthcare and less exposure to infection can all affect how tall children grow, and the study’s authors said the results highlight the need to improve children’s environments globally. A later NCD-RisC analysis also suggested that gains can slow during school age, showing that growth depends on more than infancy alone.
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