The authors did not state the overall number of studies that were included in the review, although 47 articles appear to have been included. There were 12 randomised controlled trials (RCTs) of exercise programmes to reduce falls; 5 prospective observational studies evaluating the association of usual physical activity with the risk of falling; 9 'prospective' studies and 17 case-control studies evaluating the association between physical activity and fracture; and 8 'other' studies examining the association of physical activity with other fracture sites commonly attributed to osteoporosis.
Physical activity and risk of fall.
The results from prospective, observational studies evaluating the association of usual physical activity with risk of falling were equivocal, although they may suggest a U-shaped association, in which the most inactive and active persons may be at highest risk. However, these inconsistent findings may be partially explained by differences in how physical activity was defined and measured. These observational studies also had several methodological limitations in terms of subjective measurement of physical activity and inadequate controlling for confounders.
The results from 12 RCTs of the use of exercise programmes to reduce falls were also mixed. Five of these studies were evaluated as part of a review by the Cochrane Collaboration on the use of various interventions to prevent falls in older people (see Other Publications of Related Interest). The authors concluded that exercise interventions alone were not effective in reducing the risk for falls among older adults. This review included 6 additional studies not included in the Cochrane review; of these, 4 found exercise training to be beneficial with regards to the risk of falls, whilst 2 found no benefit.
Physical activity and risk of hip fracture.
Most case-control studies of physical activity and hip fracture have shown that women with hip fractures are more likely to report being inactive in the recent past, and at earlier times in their lives, than the controls. The reductions in the odds of fracture among women engaging in moderate physical activity, compared with controls, typically ranged from 20 to 60%. However, analyses conducted among men, although reporting similar trends, tended to be underpowered. In addition, all of the studies were vulnerable to the potential biases inherent in the case-control design.
At least 8 prospective studies evaluated the association between physical activity and hip fracture risk, of which 6 found significant risk reductions among either men or women. There was variation between these studies in terms of the type of physical exercise and the overall relative risk of hip fracture. Nevertheless, the consistency, magnitude of effect, and diversity of populations across these prospective studies suggested that a physically active lifestyle can help reduce the incidence of hip fractures in the population.
Other osteoporotic fracture sites.
Few epidemiologic studies have examined the association of physical activity with other fracture sites commonly attributed to osteoporosis. One prospective study showed that among women, but not men, high levels of physical activity were related to a significant 50% increased risk of non-weight-bearing fracture sites; these included the wrist, proximal humerus, hand and finger. One case-control study conducted among European residents found that women who walked at least 30 minutes a day significantly reduced their odds of vertebral fracture by 20%; there were no significant findings among men. Another prospective study found that women who engaged in high-intensity activities, such as tennis and aerobics, were 33% less likely to have a vertebral fracture than those who did not. There were no overall significant findings for the remaining studies of these fracture sites.