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Abstract and Introduction
Abstract
The principal causal components of an osteoporotic fracture are a fall and weakened bone strength. While bone quality measures have been frequently studied, the ability of simple measures of impaired balance to predict fracture risk has received less attention. Computer-assisted telephone interviews were conducted between 1998 and 2000 among 24,598 Swedish twins aged 55 years or older. Impaired balance at the time of interview was reported by 2,890 (12%) of the twins. Twin pairs who were discordant with regard to impaired balance were selected for analysis and followed for fractures through 2005. In a pairwise analysis, the odds ratio for hip fracture was 3.13 (95% confidence interval (CI): 1.62, 6.05) among twins with impaired balance as compared with their co-twins with normal balance. When previously recognized clinical risk factors for osteoporotic fracture were considered in the model, the odds ratio for hip fracture with impaired balance was 3.88 (95% CI: 1.40, 10.72). Approximately 40% of all hip fractures were attributable to impaired balance. The odds ratios for any fracture and any osteoporotic fracture for twins with impaired balance were 2.00 (95% CI: 1.29, 3.11) and 2.39 (95% CI: 1.49, 3.82), respectively. These results imply that self-reported impaired balance is a novel and readily assessed risk factor for future fractures in the elderly.
Introduction
The principal component causes of an osteoporotic fracture are a fall and a fragile skeleton. Most research on primary prevention of these fractures has focused on bone-related risk factors. However, the vast majority of all fractures in elderly persons occur after a fall. Therefore, the risk of a future fall, not only bone quality, should be integrated into an individual risk profile for osteoporotic fracture.
Attempts to examine the value of variables related to balance and fall risk in assessing the risk of osteoporotic fracture have been few. A measured impaired balance is associated with increased risk of falls. However, even if direct measurement of balance performance might be preferable, it is not easily accomplished or reproduced. Thus, self-reports could be used as a good and simple alternative. Self-reported impaired balance is strongly associated with performance-based inferior postural stability. Measured impaired balance is an independent risk factor for osteoporotic fractures in some but not all prospective studies. Self-reported falls have also been reported as a risk factor but not an independent predictor of fracture risk.
There is a need for a simple tool with which to identify subjects who are at increased risk of injurious falls. Self-reported impaired balance might be such a readily accessible risk factor. The precise matching on age, together with control of shared genes and shared environmental influences, makes a twin design suitable for the study of an exposure effect on fracture risk. Therefore, we used data from a population-based Swedish twin registry to estimate the future risk of fractures among twins aged 55-88 years who were discordant with regard to self-reported impaired balance.
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