Secular changes in human biological variables in Western countries: an updated review and synthesis

This paper provides a review of the recent literature on some aspects of secular trends in Western countries. In particular, we discuss height variation, mainly on the basis of conscript data. There are still large height differences between European countries, and there is a marked trend for the tallest conscripts to be in northern Europe and the shortest ones in the southern part of the continent. The secular trend in adult height has come to a halt in northern Europe and Italy, while it is still in progress in Belgium, Spain and Portugal. The secular trend in height mainly depends on the increase of lower limb length. Obesity is now epidemic in Western countries, the USA population being the most affected. There is also a progressive anticipation of all the signs of puberty, namely age at menarche, appearance and development of the breasts, genitals and pubic and axillary hair, although there is ethnic/population variability in this regard. A tendency to later onset of menopause has also been recorded. Regarding secular trends in sport, there has been a progressive selection of athletes with larger body dimensions. Finally, the authors provide suggestions for future fruitful directions of the research of the secular trend in human biology.