Population-Based Study of Age and Sex Differences in Bone Volumetric Density, Size, Geometry, and Structure at Different Skeletal Sites

Abstract

In a population-based, cross-sectional study, we assessed age-and sex-specific changes in bone structure by QCT. Over life, the cross-sectional area of the vertebrae and proximal femur increased by ϳ15% in both sexes, whereas vBMD at these sites decreased by 39 -55% and 34 -46%, respectively, with greater decreases in women than in men.Introduction: The changes in bone structure and density with aging that lead to fragility fractures are still unclear. Materials and Methods: In an age-and sex-stratified population sample of 373 women and 323 men (age, 20 -97 years), we assessed bone geometry and volumetric BMD (vBMD) by QCT at the lumbar spine, femoral neck, distal radius, and distal tibia. Results: In young adulthood, men had 35-42% larger bone areas than women (p Ͻ 0.001), consistent with their larger body size. Bone area increased equally over life in both sexes by ϳ15% (p Ͻ 0.001) at central sites and by ϳ16% and slightly more in men at peripheral sites. Decreases in trabecular vBMD began before midlife and continued throughout life (p Ͻ 0.001), whereas cortical vBMD decreases began in midlife. Average decreases in trabecular vBMD were greater in women (Ϫ55%) than in men (Ϫ46%, p Ͻ 0.001) at central sites, but were similar (Ϫ24% and Ϫ26%, respectively) at peripheral sites. With aging, cortical area decreased slightly, and the cortex was displaced outwardly by periosteal and endocortical bone remodeling. Cortical vBMD decreased over life more in women (ϳ25%) than in men (ϳ18%, p Ͻ 0.001), consistent with menopausal-induced increases in bone turnover and bone porosity. Conclusions: Age-related changes in bone are complex. Some are beneficial to bone strength, such as periosteal apposition with outward cortical displacement. Others are deleterious, such as increased subendocortical resorption, increased cortical porosity, and, especially, large decreases in trabecular vBMD that may be the most important cause of increased skeletal fragility in the elderly. Our findings further suggest that the greater age-related decreases in trabecular and cortical vBMD and perhaps also their smaller bone size may explain, in large part, why fragility fractures are more common in elderly women than in elderly men.

Bone cross-sectional geometry in male runners, gymnasts, swimmers and non-athletic controls: a hip-structural analysis study

“…This supports the number of animal studies that have demonstrated periosteal expansion with increased mechanical loading (Pederson et al, 1999;LaMothe et al, 2005). Interestingly, we also found lower CSMI in gymnasts, potentially reflective of the lower age of the gymnasts, through the knowledge that bone width through periosteal apposition also increases during young adulthood (Riggs et al, 2004).…”

Gender Differences in Osteoporosis and Fractures

“…However, few studies have explicitly described these differences. Two cross-sectional studies, one [35] in older Icelandic men and women and one [32] in older residents of the Rochester, MN, area, described age-related changes in bone strength. Both studies demonstrated men have a greater cross-sectional area of bone than women, as assessed by quantitative CT [32,35].…”

“…Two cross-sectional studies, one [35] in older Icelandic men and women and one [32] in older residents of the Rochester, MN, area, described age-related changes in bone strength. Both studies demonstrated men have a greater cross-sectional area of bone than women, as assessed by quantitative CT [32,35]. They also showed older women have lower levels of volumetric bone density than men, and both genders' bone size increases with age, resulting in bone strength that worsens more in women than in men as age increases.…”

Correlates of bone quality in older persons

“…These studies neglect to consider that trabecular and cortical bones have different physiological characteristics and, therefore, are likely to be affected by different factors [2][3][4][5]. Age-related bone loss is accompanied by an increase in bone diameter, a putative adaptive mechanism that tends to maintain bone strength [6][7][8].…”