Nordic populations are still getting taller - secular changes in height from the 20th to 21st century.

Aim: The study aims to investigate secular changes in adult height among Nordic reference populations during the last four decades and in parents of Swedish study participants, and to study during which growth phase(s) infancy, childhood or puberty changes in height and tempo occurred.

Methods: Length and height data were obtained from publications on populations used as current and previous national height references in Denmark, Finland, Norway and Sweden. Measurements from birth until adult height and original parental heights of participants in Swedish reference populations born 1956, 1974, and 1990 were used.

Results: Adult height has increased progressively in Nordic populations born in 1950s-1990s; for females by 6 mm/decade Norway, 4 mm; Sweden, 6 mm; Finland and Denmark, 7 mm; for males by 9 mm/decade, in Sweden, 5 mm; Finland, 7 mm; Denmark 8 mm; Norway, 15 mm. This was due to more growth during childhood despite earlier timing of mid-puberty. Heights of Swedish parents born 1920s-1960s increased 11 mm/decade for mothers, 14 mm/decade for fathers.

Conclusion: The Nordic countries comprise some of the tallest populations in the world yet continue to show a positive secular change in adult height alongside a faster tempo of growth by earlier timing of puberty, highlighting the need to regularly update national height references.