Bone density determinants in elderly women: A twin study

Abstract

This cross-sectional twin study examined the influence of constitutional, lifestyle, and genetic factors on bone mineral density (BMD) in elderly women. BMD, at the lumbar spine, femoral neck, Ward's triangle, total hip, and total forearm, total body bone mineral content (BMC), and lean mass and fat mass were measured using dual energy X-ray absorptiometry in 69 volunteer female twin pairs (37 monozygotic [MZ], 32 dizygotic [DZ]) aged 60-89 years. Height and weight were measured. Medical history and lifetime tobacco and alcohol use were determined by questionnaire. In terms of within-pair differences, lean mass was independently associated with BMD at all sites. In contrast, fat mass was not associated with BMD at any site once allowance had been made for lean mass. Lifetime tobacco use was independently associated with BMD at the lumbar spine, total hip, and forearm. Total body BMC was independently predicted by lean mass, fat mass, tobacco use, and alcohol consumption. Age and the above independently predictive body composition and lifestyle factors accounted for 20-33% of variation in BMD. After allowing for these covariates, MZ and DZ correlations were consistent with about 75% of residual variation in BMD at the nonforearm sites being determined by genetic factors. For total body BMC, the covariates explained 75% of total variation, and genetic factors 76% of the residual variation. Therefore, at the proximal femur and lumbar spine, after taking into account the relation of BMD with lean mass and smoking, genetic factors appear to play a substantial role in explaining variation in BMD in elderly women.

Bone health in ambulatory individuals with multiple sclerosis: Impact of physical activity, glucocorticoid use, and body composition

“…This finding is consistent with previous literature in which weight was a primary predictor of WB, LS, and PF BMD [36][37][38]. Of soft tissue components, lean mass has been shown to be the strongest predictor of BMD in young women without MS [23,[39][40][41][42][43] and in adults and older women without MS [36,[44][45][46][47], whereas other studies have shown that fat mass is associated with bone health [21,23,48]. Differences between these findings may be the result of age, since this may affect soft tissue predictors of BMD, with lean mass being a stronger predictor in young women without MS and fat mass having a stronger association with BMD in postmenopausal women without MS [21][22][23].…”

A genome-wide linkage scan for low spinal bone mineral density in a single extended family confirms linkage to 1p36.3

“…T-scores express the units of SD below or above the expected bone density value of a healthy young adult of the same sex. Volumetric BMD (vBMD) (g/cm 3 ) at L1 -L4 was calculated from the bone mineral content divided by the vertebral body volume (VV). VV of L1 -L4 was calculated using the projected area of L1 -L4 obtained by anteroposterior DXA and assuming the vertebral body resembles a cube (VV ¼ (anteroposterior area) 3/2 ).…”

Recent genetic discoveries in osteoporosis, sarcopenia and obesity [Review]

“…BMD, the primary surrogate marker of osteoporosis and a major predictor of fracture risk, is a complex quantitative trait with a normal distribution in humans. Several twin and family studies have consistently shown that genetic factors account for approximately 50-90% of the interindividual variation in BMD [3][4][5]. Modest associations have been reported between BMD variations and genetic polymorphisms in or near some genes [6,7].…”