# Birth Characteristics and Bone Mineral Density and Content in Young Adults: The HUNT Study, Norway

## TL;DR

This study finds that birth characteristics like weight and gestational age are linked to stronger bones in young adults.

## Contribution

The study establishes novel associations between birth weight, ponderal index, and later bone mineral density and content in young adults.

## Key findings

- Higher birth weight and ponderal index are associated with increased bone mineral density in young adults.
- Being born large for gestational age correlates with higher bone mineral content, while low birth weight is linked to lower bone mineral content.

## Abstract

To examine the association between birth characteristics and bone mineral density (BMD) and bone mineral content (BMC) in young adults.

Data from 3,174 participants aged 20–54 years from the 3rd (2006–2008) and 4th (2017–2019) HUNT Study surveys were linked to the Medical Birth Registry of Norway. BMD and BMC of femoral neck were measured using dual-energy X-ray absorptiometry (DXA). Linear regression estimated mean differences in BMD and BMC by birth characteristics, adjusting for sex, birth year, age at scan, maternal age, and maternal morbidity.

At bone densitometry, participants had a mean age of 34.2 years, with mean BMD of 0.971 g/cm2, and mean BMC of 5.398 g, at the femoral neck. A standard deviation (SD) increase in ponderal index (PI) and birth weight was associated with higher BMD of 0.024 g/cm2 (95% CI 0.006, 0.042) and 0.015 g/cm2 (95% CI 0.009, 0.022). Individuals born large for gestational age (LGA) had 0.023 g/cm2 (95% CI 0.007, 0.039) higher BMD than those born appropriate for gestational age (AGA), while low birth weight (LBW)(< 2.5 kg) was associated with − 0.028 g/cm2 (95% CI − 0.053, − 0.003) lower BMD.

For BMC, an SD increase in PI and birth weight was associated with 0.171 g (95% CI 0.048, 0.293) and 0.146 g (95% CI 0.112, 0.181) higher BMC, respectively. LGA had 0.206 g (95% CI 0.090, 0.313) higher BMC, while LBW was associated with − 0.298 g (95% CI − 0.469, − 0.127) lower BMC.

Higher ponderal index, birth weight, and gestational age were positively associated with BMD and BMC in young adulthood.

The online version contains supplementary material available at 10.1007/s00223-025-01441-2.