Our results demonstrated that, among participants aged 50 years and older, those with hip or vertebral fractures were more likely to die during the 5 years of follow-up than were those without these fractures. In addition, our results showed that hip fractures may have long-lasting effects that result in eventual death by signaling or actually inducing a progressive decline in health. Our results also showed that vertebral fracture was an independent predictor of death. Fractures of the forearm or wrist and ribs had no impact on mortality. These findings confirm those from other studies.3,6,8,11,18,19
In contrast to studies that have shown increased mortality among men with fractures than among women with fractures,10,20
our adjusted findings showed no sex-related differences. Perceived differences may be due to other individual characteristics that are not distributed equally among men and women and not controlled for in the analyses.20
For instance, compared with women, men may have poor underlying health, more disease conditions and less social support.20
Nonetheless, our study may have had insufficient power to detect sex-related differences.
The strengths of our study are numerous. The participants were selected randomly from population lists that represent an age-, sex- and region-specific sample of the Canadian population. A large number of women and men across Canada were evaluated, which improves the generalizability of the results. Radiographs were systematically performed at baseline to confirm all prevalent vertebral fractures. We examined several types of osteoporotic fractures, including the infrequently studied pelvic and rib fractures. Furthermore, because mortality and fractures are largely a problem of older people with comorbidities, we adjusted our analysis for factors that may influence mortality, such as the number of diseases, use of medications, health-related habits and quality of life.
The distinct characteristics of our study, which previous studies examining the relation between fracture and mortality have lacked, strengthen our ability to suggest a causal relation between fractures and mortality. First, the strength of the associations was strong, with the majority of significant HRs being about 3. Thus, it is unlikely that the associations were by chance. Temporally, the relation is correct, fractures precede death. In addition, the associations differed depending on the type of fracture. We found that only vertebral and hip fractures were associated with death. Moreover, the relation between fracture and death is biologically plausible, and theories exist as to why fractures cause death. For example, 2 theories have been proposed to clarify the association between hip fractures and death. The first suggests that frail elderly people who have a number of comorbidities will die quickly following a fracture. A hip fracture is simply one event in a series of late-life illnesses that increases such a person’s likelihood of dying. The second theory involves healthy elderly people without notable comorbidities. Such people are better able to endure the initial consequences of a hip fracture because of their superior health and coping abilities. Their progressive decline in health may be caused by a lack of mobility and a loss of strength and muscle mass, which results in increased disability and other negative health consequences.11
Vertebral fractures probably influence death directly because of their association with chronic back pain, immobility and change in posture, which may increase the risk of infection.21
Finally, fractures have been found to have many other negative consequences such as increased pain, immobility and reduced health-related quality of life.
Our finding that participants with fractures in the “other” category during the fourth or fifth year of follow-up were less likely to die than those without such fractures is difficult to interpret. This is because of the large number of types of fracture in this category and the potential differences in rates of death associated with individual fracture types.
We found that several other factors were related to mortality. As expected, smoking status, regular physical activity and number of diseases had a major impact on mortality. Participants with at least some university education were less likely than those with no university education to die during the follow-up period. It has been postulated that people with lower education levels are at increased risk of death because of their lower socio-economic status.22,23
Our study has limitations. Although we included several potential confounding variables in the analysis, not all risk factors may have been adequately captured in the Canadian Multicentre Osteoporosis Study data set. In addition, only new, clinically recognized vertebral fractures were examined (not vertebral fractures identified on the basis of morphometric measurements). Thus, a large proportion of incident vertebral fractures may not have been recognized. However, it has been shown that radiographically identified vertebral fractures have less impact on mortality than clinically recognized fractures and thus may not be important.24
Moreover, because of the small number of fractures at certain anatomic sites, particularly in men, and the fewer men than women in the stratified recruitment sample, results were inconclusive (given the wide CIs). Furthermore, because of the limited number of multiple fractures by fracture type, we could not address the influence of multiple fractures on mortality. Finally, the study involved ambulatory participants living in the community. We did not evaluate the relation between hip fractures and short-term mortality among people in long-term care facilities, who are likely more frail.
Our results show a strong association between vertebral and hip fractures and death. Given this association, interventions need to be implemented to reduce the likelihood that patients will experience fractures that increase their risk of death. These might include the use of interventions such as osteoporosis medications, strategies to prevent falls or the use of hip protectors.