Bone loss varies with gender, accelerates with age
MedWire News: The rate of bone loss is markedly higher in women than in men and increases with age in both genders, a study of older Icelandic individuals suggests.
Gunnar Sigurdsson (Landspitali University Hospital, Reykjavik, Iceland) and team studied 1838 men and 1924 women aged 66-96 years who were participating in the prospective Age/Gene/Environment-Susceptibility (AGES)-Reykjavik study.
At baseline all participants underwent computed tomography of the mid-thigh, and Sigurdsson's team used these data to investigate the relationship between muscle and bone parameters and how these parameters relate to osteoporotic fracture risk.
The participants' mean age at baseline was 76.5 years and they were followed up for a median of 5.3 years. During this time there were 113 low-impact fractures in women and 66 such fractures in men, most of which involved the hip.
Analysis of muscle parameters revealed that the total cross-sectional muscular area and knee extensor strength declined with age to a similar extent in men and women. After adjusting for age, height, and weight, muscle parameters were positively correlated with cortical area and total shaft area but nevertheless explained less than 10% of variability.
With respect to bone parameters, total shaft area was unchanged with age in both men and women whereas medullary area and buckling ratio each rose markedly with advancing age. The increment in the latter two parameters was around fourfold higher in women than in men.
Medullary area was not correlated with muscle parameters, however.
Finally, multivariate analysis identified five baseline characteristics that were significantly and independently predictive of fracture risk in both men and women: small muscular area; low knee extensor strength; large medullary area; low cortical thickness; and high buckling ratio.
"Our results support the notion that endocortical resorption may be a key process for the development of bone fragility in lower limbs in old age," write Sigurdsson et al in Calcified Tissue International.
"Better understanding of the determinants of endocortical resorption might thus be of importance in the prevention of low-trauma lower limb fractures in older people."
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By Joanna Lyford