Is there an association between birth characteristics and fractures in young adults? The HUNT Study, Norway.

Unlabelled: This population study investigated the association between birth characteristics and fracture risk in 11,099 young adults (aged 19-54 years). Our findings indicate that birth weight, gestational age, and birth weight for gestational age were not associated with fractures in the wrist, humerus, hip, and spine in this population.

Purpose: Skeletal development starts during fetal life, and it is estimated that most bone formation occurs in the 3rd trimester. This study examined the association between birth characteristics and fractures of the wrist, humerus, hip, and spine, in young adults (19-54 years).

Methods: 11.099 participants in the 3 survey of the HUNT Study (2006-2008) were linked with the Medical Birth Registry of Norway and hospital records. Fractures of the wrist, humerus, hip, and spine were identified using ICD9/10 codes between 1988 and 2021. Follow-up was from date of participation in HUNT until a first fracture, emigration, death, or end of study. Cox regression was used to estimate hazard ratios (HR) of fracture associated with birth characteristics (95% CI), adjusted for birth year, sex, maternal age, and maternal morbidity. In a secondary analysis, follow-up started in 1988.

Results: During a median follow-up of 14.0 years (153,657 person-years), 290 fractures occurred. Mean age at first fracture was 41.4 years (SD 7.4). Overall, there were no clear associations between birth characteristics and fractures in these data. HR for fracture was 0.43 (0.15-1.24) for those with a birth weight < 2.5 kg (reference birth weight 3.5 - 3.9 kg); 1.04 (0.74 - 1.46) for those born small for gestational age (< 10th percentile, reference 10 - 90 percentile); and 0.63 (0.33 - 1.23) for those born preterm (reference term births). The secondary analysis from 1988, including 539 fractures, gave similar results as the main analysis.

Conclusion: Birth weight, gestational age, or birth weight for gestational age was not associated with an increased risk of fractures of the wrist, humerus, hip, and spine in young adults.