Secular Trend and Socioeconomic Variation in Body Height of Young Polish Men Between 1965 and 2023

Secular trends in body height reflect changes in living conditions and population health, while socioeconomic gradients in height indicate persistent inequalities in growth opportunities. The aim of this study was to examine secular trends and socioeconomic variation in height among young adult Polish men between 1965 and 2023.

Data included nationally representative surveys of Polish military conscripts conducted in 1965, 1986, 1995, 2001, 2010, and 2023 (N = 137 551). Body height was measured and socioeconomic status (SES) was estimated by questionnaire using four indicators: urbanization level (city, town, village), mother's and father's education (university, secondary, vocational, elementary), and family size (1-2, 3, and 4 or more children). Overall SES was estimated with principal component analysis and divided into three categories: high, medium, low. Statistical analyses included one-way and two-way ANOVAs with Tukey post hoc tests for unequal samples; effect sizes were expressed as partial eta squared (η²).

Mean height increased significantly across successive surveys (p < 0.0001), with the largest gains between 1965 and 1986. The secular trend progressively decelerated, with minimal increases observed between 2010 and 2023. Socioeconomic variation in height declined over time but remained statistically significant for most SES indicators in 2023, except for urbanization (p > 0.05). The reduction in differences was largely due to greater height gains among lower SES groups after 2001. Note, however, effect sizes for all SES factors were small: partial η² values from 0.008 to 0.012, and medium for the year of survey: η² values from 0.040 to 0.125.

The continued but slowing increase in body height suggests that Polish men are approaching population growth potential. However, persistent socioeconomic differences in terms of parental education and family size imply that individuals from lower socioeconomic strata still retain potential for biological catch-up.