Search:
Menopause Live - IMS Updates
InFocus

Date of release: 10 August, 2009

High weight or body mass index increases the risk of vertebral fracture


In the general population, low body weight and body mass index (BMI) are known and significant risk factors for any fracture, but the specific association between body weight, BMI, and prevalence of vertebral fractures in osteoporotic women is not fully recognized. In a paper recently published in Journal of Bone and Mineral Metabolism, Pirroand colleagues [1] suggest that, among postmenopausal women with osteoporosis, body weight and BMI are associated with a higher likelihood of having a vertebral fracture, irrespective of the positive association between weight and bone mineral density. Hence, the association between body weight, BMI and prevalent vertebral fractures was investigated in 362 women with never-treated postmenopausal osteoporosis. All participants underwent measurement of BMI, bone mineral density and semi-quantitative assessment of vertebral fractures. Thirty percent of participants had one or more vertebral fractures. Body weight and BMI were associated with L1–L4 bone mineral density (R = 0.29, p < 0.001 and R = 0.17, p = 0.009, respectively). According to statistical analysis, BMI and weight were positively associated with the presence of vertebral fractures independent of age and other traditional risk factors (age, height, early menopause, smoking and family history of fragility fractures).

Comment

Body weight and BMI correlate with bone density and strength. Obese women usually have a higher bone density and are regarded as less vulnerable for fragility fractures. On the other hand, low body weight and low BMI have long been recognized as risk factors for osteoporosis, particularly when they are present early in life, and multiple studies have confirmed this. 
Young women who are constitutionally thin, or naturally severely thin, with no identified eating disorder, normal physiological menstrual cycles and normal energy metabolism, but who have a low body mass index may have impaired bone quality and be at increased risk for osteoporosis. Anorexic patients, with identified eating disorders and decreased bone mass, have a very increased fracture risk, which is explained by the multiple hormonal and nutritional abnormalities, as well as low body weight and BMI.
During the reproductive years, a significantly lower body weight and body mass index in the puerperium can be associated with osteopenia, compared to normal women [2].
Prospective studies to determine factors for fragility fractures in elderly women (Rotterdam Study and Longitudinal Aging Study Amsterdam) found that low body weight and BMI were not associated with fragility fracture [3]. In contrast, the paper by Pirro and colleagues [1] proposes that, in osteoporotic women, high body weight and body mass index are considered risk factors for vertebral fractures. Body weight impacts on bone turnover and bone density, making it, therefore, an important risk factor for vertebral and hip fractures and ranking it alongside age in importance. In postmenopausal women, the body weight is mainly determined by fat mass; the lean mass is not so important. There is an association of fat mass with the secretion of bone-active hormones from the pancreatic beta cell (including insulin, amylin and preptin). The fat–bone relationship is also affected by the secretion of bone-active hormones and adipokines (e.g. estrogens and leptin) from the adipocyte and its participation in bone remodeling through effects on deposition and resorption. These factors alone probably do not fully explain the observed clinical associations, and study of the actions on bone of novel hormones related to nutrition is an important area of further research [4]. 
On the other hand, the skeleton has recently emerged as an endocrine organ with effects on body weight control and glucose homeostasis through the actions of bone-derived factors such as osteocalcin and osteopontin. The relationship between adipose tissue and the skeleton constitutes a homeostatic feedback system, with adipokines and molecules secreted by osteoblasts and osteoclasts representing the links of an active bone–adipose axis [5].
The recent introduction of bariatric surgery impacts on the metabolic aspects of bone, since the considerable weight loss following surgery causes changes in metabolism. Thus, this dynamic system merits detailed consideration [6].
More immediately, the role of normal weight maintenance in the prevention of osteoporosis and fractures is an important public health message that needs to be more widely appreciated.

Comentario

Elena Calle Teixeira
Department of Obstetrics and Gynaecology, ‘San Pablo Clinic, Lima, Peru

    References

  1. Pirro M, Fabbriciani G, Leli C, et al. High weight or body mass index increase the risk of vertebral fractures in postmenopausal osteoporotic women. J Bone Miner Metab 2009; July 4 (E-pub ahead of print).
    http://www.ncbi.nlm.nih.gov/pubmed/19578807

  2. Kurabayashi T, Nagata H, Takeyama N, Matsushita H, Tanaka K. Bone mineral density measurement in puerperal women as a predictor of persistent osteopenia. J Bone Miner Metab 2009;27:205-12.
    http://www.ncbi.nlm.nih.gov/pubmed/19172224

  3. Pluijm SM, Steyerberg EW, Kuchuk NO, et al. Practical operationalizations of risk factors for fracture in older women: results from two longitudinal studies. J Bone Miner Metab 2009;24:534-42. Published March, 2009.
    http://www.ncbi.nlm.nih.gov/pubmed/18597634

  4. Reid IR. Relationships between fat and bone. Osteoporos Int 2008;19:595-606.
    http://www.ncbi.nlm.nih.gov/pubmed/17965817

  5. Gómez-Ambrosi J, Rodríguez A, Catalán V, Frühbeck G. The bone-adipose axis in obesity and weight loss. Obes Surg2008;18:1134-43.
    http://www.ncbi.nlm.nih.gov/pubmed/18563500

  6. Olmos JM, Vázquez LA, Amado JA, Hernández JL, González Macías J. Mineral metabolism in obese patients following vertical banded gastroplasty. Obes Surg 2008;18:197-203.
    http://www.ncbi.nlm.nih.gov/pubmed/18188655