ABSTRACT
Areal bone mineral density (aBMD) is the most common estimate of bone mass, incorporated in the World Health Organization definition of osteoporosis. However, aBMD depends on not only the amount of mineral but also the bone size. The estimated postmenopausal decline in aBMD could because of this be influenced by changes in bone size.We measured bone mineral content (BMC; mg), aBMD (mg/cm2), and bone width (mm) by single-photon absorptiometry at the cortical site of the forearm in a population-based sample of 105 Caucasian women. We conducted 12 measurements during a 28-yr period from mean 5 yr (range: 2-9) before menopause to mean 24 yr (range: 18-28) after menopause. We calculated individual slopes for changes in the periods before menopause, 0-<8, 8-<16, and 16-28 yr after menopause. Data are presented as means with 95% confidence intervals. The annual BMC changes in the 4 periods were -1.4% (-0.1, -2.6), -1.1% (-0.9, -1.4), -1.2% (-0.9, -1.6), and -1.1% (-0.8, -1.4) and the annual increase in bone width 0.4% (-1.2, 1.9), 0.7% (0.5, 0.9), 0.1% (-0.2, 0.4), and 0.1% (-0.2, 0.4). BMC loss was similar in all periods, whereas the increase in bone width was higher in the first postmenopausal period than in the second (p=0.003) and the third (p=0.01) postmenopausal periods. Menopause is followed by a transient increase in forearm bone size that will influence the by aBMD estimated cortical loss in bone minerals.
Subject(s)
Arm Bones/diagnostic imaging , Bone Density , Forearm , Osteoporosis, Postmenopausal , Absorptiometry, Photon/methods , Aged , Arm Bones/metabolism , Arm Bones/pathology , Female , Follow-Up Studies , Humans , Middle Aged , Organ Size , Osteoporosis, Postmenopausal/diagnosis , Osteoporosis, Postmenopausal/epidemiology , Osteoporosis, Postmenopausal/metabolism , Postmenopause , Prospective Studies , Sweden/epidemiologyABSTRACT
OBJECTIVE: Identify risk factors for fragility fractures and mortality in women aged 48. STUDY DESIGN: Prospective population-based observational study on 390 white north European women aged 48 at study start. At study start, we measured bone mineral density (BMD) by single-photon absorptiometry (SPA) in the distal forearm, anthropometry by standard equipment and registered menopausal status, health and lifestyle factors. Menopause before age 47 was defined as early menopause. Incident fragility fractures and mortality were recorded until the women reached age 82. Potential risk factors for fragility fracture and mortality were evaluated with Cox's proportional hazard regression analysis. Data are presented as risk ratios (RR) with 95% confidence intervals in brackets. MAIN OUTCOME MEASURES: Incidence of fragility fractures and mortality. RESULTS: In the univariate analysis, low BMD and early menopause predicted fractures. In the multivariate analysis, only BMD remained as an independent risk factor with a RR of 1.36 (1.15, 1.62) per standard deviation (SD) decrease in baseline BMD. In the univariate analysis, early menopause and smoking predicted mortality, and remained as independent risk factors in the multivariate analysis with RR 1.62 (1.09, 2.39) for early menopause and 2.16 (1.53, 3,06) for smoking. CONCLUSIONS: Low BMD at age 48 is an independent predictor for fragility fractures. The predictive ability of early menopause is at least partially attributed to other associated risk factors. Early menopause and smoking were found in this study to be independent predictors for mortality.
