Bone Abstracts

Early life growth has been suggested to influence bone health. However, the relationship with risk of hip fracture in old age has not been thoroughly investigated. We therefore studied the association between birth weight and hip fracture incidence after age 50 among 10 893 men and women (48% women) from the Uppsala Birth Cohort Study (UBCoS, born 1915–1929) and 1334 men from the Uppsala Longitudinal Study of Adult Men (ULSAM, born 1920–1924). Birth weight was collected from hospital or midwives’ records and hip fractures were obtained from the Swedish Hospital Discharge Register.

We observed 717 hip fractures in UBCoS (458 in women, 259 in men, end of follow-up: 31 December 2008) and 102 hip fractures in ULSAM (end of follow-up: 31 December 2009). There were no indications of non-linear associations. Results are presented as hazard ratios (HR) and 95% CI per 1 kg increase in birth weight.

The crude HR for 1 kg increase in birth weight on hip fracture rate in UBCoS was 0.99 (95% CI: 0.85–1.14). After controlling for gender and socioeconomic status at birth, the HR was 1.06 (95% CI: 0.91–1.23). Additional adjustment for adult height and comorbidity in a subgroup of UBCoS men (n=1241, 50 hip fractures) gave a HR of 0.97 (95% CI: 0.52–1.80). Parity and gestational age did not largely influence the estimates. Neither birth weight standardized for gestational age nor gestational duration was associated with hip fracture rate.

The unadjusted HR in ULSAM was 1.06 (95% CI: 0.73–1.53). After adjustment for adult body mass index, height, social class, comorbidity, and smoking status, the HR was 1.03 (95% CI: 0.70–1.51).

Based on the results from two population-based cohorts with accurate assessment of both birth weight and hip fractures, we conclude that there is no association between birth weight and risk of hip fracture.