Rate of bone loss is associated with mortality in older women: a prospective study

Older women with low bone density have an increased risk of fracture, cardiovascular disease, and mortality. However, it is not known whether this association is caused by ongoing bone loss or by lower bone mass earlier in life. To determine whether rate of bone loss is associated with total and cause-specific mortality, we prospectively studied 6046 women aged 65 years or older who had serial bone mineral density (BMD) measurements as a part of the Study of Osteoporotic Fractures. Rates (mean +/- SD) of loss of BMD at the heel (for a mean of 5.7 years) and hip (for a mean of 3.5 years) were estimated. Cause-specific mortality was ascertained from death certificates and hospital records. BMD loss at the heel was 5.9 +/- 6.0 mg/cm2 per year (1.5 +/- 1.5%) and BMD loss at the hip was 4.1 +/- 10.2 mg/cm2 per year (0.6 +/- 1.4%). During an average follow-up of 3.2 years after the second measurement of BMD, 371 deaths occurred. Each SD increase in BMD loss at the hip was associated with a 1.3-fold (95% CI, 1.1-1.4) increase in total mortality, adjusted for age, baseline BMD, diabetes, hypertension, incident fractures, smoking, physical activity, health status, weight loss, and calcium use. In particular, hip BMD loss was associated with increased mortality from coronary heart disease (relative hazard [RH] = 1.3 per SD; 95% CI, 1.0-1.8) and pulmonary diseases (RH = 1.6 per SD; 95% CI, 1.1-2.5). The findings were similar for bone loss at the heel, except there was no significant association with pulmonary mortality. These results raise the possibility that bone loss may share common etiologies with coronary and pulmonary diseases.