Prevalence of sarcopenia and its association with osteoporosis in 313 older women following a hip fracture
Introduction
Changes in body composition, including a decrease in both muscle and bone mass, accompany aging, as stated by several longitudinal studies (Frontera et al., 2000, Visser et al., 2003, Kanis et al., 2008a). The loss of muscle mass is thought to affect functional ability given the positive association between muscle mass and lower extremity function, and the negative association between muscle mass and risks of use of cane or walker, self-reported difficulties in activities of daily living and gait, and a history of falling (Baumgartner et al., 1998, Melton et al., 2000, Sternfeld et al., 2002, Castillo et al., 2003, Newman et al., 2003, Janssen et al., 2004a, Janssen, 2006). The loss of bone mass is a potent risk factor for fragility fractures that in turn cause loss of ability to function, dependency, and increased risk of institutionalization (Clinician's Guide, 2008, Di Monaco, 2008, Kanis et al., 2008a). Abnormally elevated muscle loss associated with qualitative changes of the muscle, resulting in loss of strength and function, characterizes sarcopenia (Baumgartner et al., 1998, Thompson, 2009). Abnormally high bone loss associated with qualitative alterations of the bone tissue resulting in bone fragility depicts osteoporosis (Clinician's Guide, 2008, Kanis et al., 2008a). The genesis of both sarcopenia and osteoporosis is multifactorial. Interestingly, several factors that play a role in the origin of osteoporosis are thought to contribute in causing sarcopenia. These putative causal factors include a decreased level of physical activity, hormonal changes (mainly low levels of sex steroids, growth hormone and insulin-like growth factor-I), a reduction in dietary protein, and catabolic stimuli from chronic inflammation (Kamel et al., 2002, Roubenoff, 2003, Evans, 2004, Kanis et al., 2008a, Pereira et al., 2009). Furthermore, a role of genetic factors in linking muscle and bone mass has been advocated (Karasik and Kiel, 2008). A common etiology may be responsible for a positive association between osteoporosis and sarcopenia, two conditions that may act together in the genesis of disability, imposing a relevant economic burden on healthcare services (Janssen et al., 2004b, Kanis et al., 2008a, Kanis et al., 2008b, Weigl et al., 2008).
Hip-fracture patients are frail subjects at high risk of disability: up to 25% of the patients who sustain a hip fracture may require long-term nursing home care and only 40% fully regain their pre-fracture level of independence (Clinician's Guide, 2008). Poor functional outcome contributes to the designation of hip fracture as a major public health problem in Western society (Kanis et al., 2008a). Osteoporosis causes bone fragility and is a well recognized major risk factor for hip fracture (Clinician's Guide, 2008, Kanis et al., 2008a). Sarcopenia increases the hazard of falling. Falls enhance hip-fracture risk (Roubenoff and Hughes, 2000, Castillo et al., 2003) and may cause disability even after successful rehabilitation following hip-fracture occurrence (Di Monaco et al., 2009a). Prevalence of sarcopenia in hip-fracture subjects is largely unknown, and the association between sarcopenia and osteoporosis has not been defined in the patients who sustain a fracture of the hip. Our aim was to investigate the prevalence of sarcopenia and the association between sarcopenia and osteoporosis in a large sample of women who sustained a hip fracture.
Section snippets
Patients and setting
The study was performed in a city with about one-million inhabitants. We evaluated 340 white women consecutively admitted to our physical medicine and rehabilitation division because of their first hip fracture. We focused on white women because few non-white elderly women live in Italy. Seventeen of the 340 women we evaluated were excluded from our study because their hip fractures resulted from either major trauma or cancer affecting bone. The remaining 323 women sustained fractures that were
Results
Descriptive statistics for the 313 women are shown in Table 1. At a Pearson's test, we found a significant positive correlation between aLM/height2 and BMD assessed at both total proximal femur (r = 0.333; p < 0.001) and femoral neck (r = 0.257; p < 0.001), as shown in Fig. 1. A total of 180 of the 313 women (i.e., 58%) were sarcopenic, whereas 230 (i.e., 73%) were affected by osteoporosis, as shown in Table 2. A χ2-test for independence showed a significant association between sarcopenia and
Discussion
We show that sarcopenia was significantly associated with osteoporosis in a large sample of women following a fragility fracture of the hip. To our knowledge this result is original, because no previous reports investigated the association between sarcopenia and osteoporosis in hip-fracture survivors, who are affected by the main clinical consequence of the combination of bone fragility and falls, resulting in a very high risk of permanent disability. A similar significant association was shown
Conclusions
We show the high prevalence of sarcopenia and a significant association between sarcopenia and osteoporosis in a large sample of hip-fracture women. Data supports a research approach on preventive strategies and treatment options for sarcopenia and osteoporosis targeting both bone and muscle tissue, although cross-sectional design does not prove causal inference. Furthermore, data should be considered when the economic burden of sarcopenia is estimated, given the high proportion of bone
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