Determinants of changes in bone mass and femoral neck structure, and physical performance after menopause: a 9-year follow-up of initially peri-menopausal women
This prospective study set out to determine factors that underlie changes in bone characteristics and physical performance during postmenopausal years. Of 101 peri-menopausal women that originally participated in a randomized, controlled exercise intervention trial, 80 attended the follow-up measurements 9 years later. At follow-up, bone mineral content (BMC) of the lumbar spine, femoral neck and distal radius, as well as the maximal isometric muscle strength of leg extensors and arm flexors, and maximal oxygen uptake, were measured with the same protocols and devices as at the baseline. In addition, the hip structure analysis (HSA) was used to assess changes in the structure and strength at the narrowest section of the femoral neck. Changes in physical fitness or bone characteristics were independent of the original exercise intervention. In general, physical fitness declined with age from 5% to 30% and bone characteristics from 3% to 10%, except for the lumbar spine BMC and the periosteal diameter of the femoral neck, where no changes were observed. The use of hormone therapy (HRT) was the major factor accounting for the maintenance of BMC. Use of HRT alone explained 44% of the variability in the change at the femoral neck BMC, but it was not associated with changes in physical fitness. Change in the body weight was the only factor associated with the change in physical fitness: better maintenance in body weight predicted better maintenance of physical fitness. In conclusion, our results indicate that HRT helps to maintain bone mass and structure, which are important factors in prevention of fragility fractures in later life. However, HRT had no effect on physical fitness, which is highly associated with the risk of falling, the most important cause of fractures.