To the authors’ knowledge, this is the first study to describe the incidence of subsequent fracture in nursing home residents with a hip fracture. It was found that the cumulative incidence of subsequent fracture was 12.1% by 1 year and 21.1% by 5 years. Mortality was even greater, with 31.4% of participants dying within 1 year and 60.1% within 5 years of a baseline hip fracture. High functional status was associated with a five times greater risk of subsequent fracture, whereas characteristics such as age, sex, cognitive status, and medication use did not predict subsequent fracture.
Prior studies from a sample of U.S. nursing homes estimated the incidence rate of osteoporotic fracture in men and women as 3.5 to 6.0 cases per 100 person-years.18,19
In studies of female nursing home residents, the incidence rate of fracture was even higher (10.9–11.5 cases/100 person years).4,20
Despite the high mortality observed after a hip fracture in the current study, a similarly high incidence rate of subsequent fracture was found in male and female nursing home residents (11.2 cases/100 person-years). This highlights the importance of addressing primary and secondary osteoporotic fracture prevention in the nursing home setting.
The incidence of subsequent fracture of all types was found to be greatest in the first year after a hip fracture (12.1%). In contrast, community-based studies have shown a low occurrence of second hip fracture within 1 year of a baseline hip fracture (1.0–2.5%).21,22
The fact that all subsequent fracture types were considered rather than second hip fracture alone may in part explain the differences in these results. Given that hip fractures accounted for nearly half of all subsequent fracture types, this is unlikely to completely explain these findings. An alternative explanation is that participants in the current study were older than community-based subjects, with a greater prevalence of dementia and functional impairment. As a result, study participants may have been at greater risk for delirium and functional decline than community dwellers, resulting in greater opportunities for subsequent falls and fracture in the months immediately after a hip fracture.
Mortality after a hip fracture was found to be greater than the incidence of subsequent fracture throughout follow-up. Six-month (23.0%) and 1-year (31.4%) mortality in nursing home residents with a hip fracture was 1.6 times as great as mortality in community-dwellers.7,23
This is consistent with at least one other cohort study in which 26% of residents with a hip fracture died within 6 months.3
Because risk of mortality is higher than the risk of subsequent fracture, identifying nursing home residents who are likely to survive will help target secondary prevention to residents most likely to benefit from interventions.
Risk factors for fracture in nursing home residents are similar to those reported for community dwellers and include older age, female sex, dementia, a prior history of falls or fracture, psychotropic medications, urinary continence, and low bone mineral density.19,24,25
Given the high morbidity and mortality associated with hip fractures in the nursing home, it is unclear whether these traditional risk factors for fracture are also predictive of subsequent fracture in frail nursing home residents.
Consistent with community-based studies of second hip fracture, the current study found that nursing home residents with high baseline functional status were more likely to experience a subsequent fracture than residents with low functional status.21
This may not be surprising, given that high-functioning individuals are more likely to engage in activities that increase the opportunity for falls. Because a measure of physical activity was not available, it was not possible to test the hypothesis that the greater risk of subsequent fracture in high-functioning persons was mediated through physical activity. At the same time, low-functioning individuals may be more likely to become immobile or die after a hip fracture, resulting in fewer opportunities for future falls and fractures. In the current study, low functional status was associated with 60% greater mortality than high functional status (results not shown). The association between high functional status and the risk of subsequent fracture persisted even after controlling for the competing risk of death. Thus, in nursing home residents, high functional status appears to predict subsequent fracture independent of survival.
Functional status may deteriorate after a hip fracture. Thus, the present analysis may not accurately represent the association between functional status and subsequent fracture in persons who experience functional decline. For example, a high-functioning resident who becomes bed-bound after a hip fracture may no longer be at greater risk for falls and subsequent fracture. A sensitivity analysis using information on functional status obtained after the fracture supports this hypothesis, because the association between high functional status and subsequent fracture was unchanged.
It is therefore recommended that all high-functioning residents with a hip fracture should be assessed for modifiable risk factors for falls. Although prescribing calcium and vitamin D is a reasonable first step in an effort to reduce subsequent fractures, the role of pharmacological agents in nursing home residents for the secondary prevention of fracture is not well defined.
Older age, female sex, anatomic site, type of repair, low BMI, comorbidities, or cognitive impairment were not found to increase the risk of subsequent fracture. In community dwellers, older age, dementia, and weight loss have been associated with a greater risk of subsequent fracture.21,26,27
In the current study, higher BMI tended to be protective against subsequent fracture, but these results were not statistically significant. These null findings may reflect an inability to detect a statistically significant association because of the small sample size and possibly because of the relative homogeneity in the distribution of baseline characteristics in study participants compared with community dwellers.6,21
Supplemental calcium, vitamin D, and osteoporosis medication use were not predictive of subsequent fracture in this study. No prior studies have specifically addressed the role of calcium and vitamin D in the secondary prevention of fractures, but supplementation with calcium and vitamin D has been associated with a 33% lower risk of nonvertebral fractures in ambulatory nursing home residents.28
It is likely that the small sample size explains the null findings, with even fewer subjects receiving osteoporosis treatment. It is also possible that calcium, vitamin D, and osteoporosis medications may not affect bone fragility soon enough to prevent subsequent fractures that occur during the first year, particularly in frail nursing home residents. Another explanation is that these treatments may have preferentially been given to individuals at highest risk of subsequent fracture.
A unique aspect of this study is that it used the CICR estimate to determine the incidence of subsequent fracture.13,14,29
Most prior studies of subsequent fracture have relied on Kaplan-Meier estimates, which assume that persons who are lost to follow-up for any reason are censored and that censored subjects remain at risk for the outcome for the duration of the study.13
However, subjects who are censored because of death are no longer capable of experiencing a subsequent fracture. By failing to account for the competing risk of death, traditional methodolological approaches can overestimate the frequency of events in the remaining population.29
It is important to describe the incidence and timing of subsequent fracture in nursing home residents accurately because this has clinical implications for secondary fracture prevention efforts. Using a CICR approach, the cumulative incidence of subsequent fracture was calculated as 12.1% by 1 year, 15.8% by 2 years, and 21.1% by 5 years. If a Kaplan-Meier estimate had instead been used, the incidence of subsequent fracture would have been calculated as 15.5% at 1 year, 21.5% at 2 years, and 35.5% at 5 years. A CICR approach more closely reflects the true risk of subsequent fracture in nursing home residents with a hip fracture.
This study has several limitations. First, the sample size was small. Nonetheless, there are few studies in nursing home residents with hip fracture and none that describe the incidence of subsequent fracture in this highly vulnerable population. Second, it was not possible to ascertain hip fractures that occurred before 1999 or fractures that occurred at other nursing home facilities for residents who may have transferred. Transfers from other facilities are not common, and it is unlikely that this would have influenced the results greatly. Third, information on most potential predictors were collected from administrative data sets (MDS). All clinical staff at Hebrew Rehabilitation Center responsible for MDS data entry undergo annual training specific to the MDS, making the quality of the data better than at most nursing homes. Finally, this study was conducted at a single nursing home. No major administrative or nursing changes in the care of residents with hip fracture occurred during the study, but the results may not be generalizable to all nursing home populations. Compared with nursing homes nationwide, HRC has a similar sex distribution (75% women), although the residents of HRC are older (88 vs 84), and a greater proportion are white (98% vs 88%).30
Despite these limitations, this study is important because it is the first to describe the incidence, timing, and predictors of subsequent fracture after a hip fracture in nursing home residents. All hip fractures were confirmed through medical record review. In addition, the study used a CICR approach to describe the incidence and measures of association of subsequent fracture, which is a more-valid time-to-event approach in the presence of competing risks.
In conclusion, this study demonstrates that hip fractures are a sentinel event in nursing home residents, with a high incidence of subsequent fracture and death occurring within 1 year. Because the risk of death is greater than the risk of subsequent fracture, identifying prefracture characteristics and postfracture complications associated with mortality is greatly needed. Establishing these risk factors should lead to better recognition of nursing home residents with sufficient life expectancy to benefit from osteoporosis medications.