Curr Osteoporos Rep DOI 10.1007/s11914-015-0274-z
NUTRITION, EXERCISE, AND LIFESTYLE IN OSTEOPOROSIS (CM WEAVER AND R DALY, SECTION EDITORS)
Fall and Fracture Risk in Sarcopenia and Dynapenia With and Without Obesity: the Role of Lifestyle Interventions David Scott 1,2 & Robin M. Daly 3 & Kerrie M. Sanders 2,4 & Peter R. Ebeling 1,2
# Springer Science+Business Media New York 2015
Abstract Due to their differing etiologies and consequences, it has been proposed that the term Bsarcopenia^ should revert to its original definition of age-related muscle mass declines, with a separate term, Bdynapenia^, describing muscle strength and function declines. There is increasing interest in the interactions of sarcopenia and dynapenia with obesity. Despite an apparent protective effect of obesity on fracture, increased adiposity may compromise bone health, and the presence of sarcopenia and/or dynapenia (Bsarcopenic obesity^ and Bdynapenic obesity^) may exacerbate the risk of falls and fracture in obese older adults. Weight loss interventions are likely to be beneficial for older adults with sarcopenic and dynapenic obesity but may result in further reductions in muscle and bone health. The addition of exercise including progressive resistance training and nutritional strategies, including protein and vitamin D supplementation, may optimise body composition and muscle function outcomes thereby reducing falls and fracture risk in this population.
Keywords Sarcopenia . Dynapenia . Obesity . Falls . Fractures . Lifestyle
Introduction Ageing is associated with progressive declines in the skeletal muscle mass and quality and concomitant increases in fat mass, which have significant metabolic and functional consequences [1]. Falls and fracture are a common concern for many older people, with low muscle mass (Bsarcopenia^) and muscle strength (Bdynapenia^) both implicated as risk factors for these outcomes. However, when combined with obesity (Bsarcopenic obesity^ or Bdynapenic obesity^), the associations are unclear due to a lack of prospective studies and controversy on the role of fat mass in falls and fracture risk [2]. Obese older people have higher fall risk than non-obese but may have reduced fracture risk due to greater bone strength and/or the protective effect of higher amounts of soft tissue. Nevertheless, with the
This article is part of the Topical Collection on Nutrition, Exercise, and Lifestyle in Osteoporosis * David Scott [email protected] Robin M. Daly [email protected] Kerrie M. Sanders [email protected]
Medical Centre, Monash University, 246 Clayton Road, Clayton, VIC, Australia 3168 2
Melbourne Medical School (Western Campus) and Australian Institute for Musculoskeletal Science, Sunshine Hospital, The University of Melbourne, 176 Furlong Road, St Albans, VIC, Australia 3021
3
Centre for Physical Activity and Nutrition Research, School of Exercise and Nutrition Sciences, Deakin University, 221 Burwood Highway, Burwood, VIC, Australia 3125
4
Institute for Health and Ageing, Australian Catholic University, Level 6, 215 Spring Street, Melbourne, VIC, Australia 3000
Peter R. Ebeling [email protected] 1
Department of Medicine, School of Clinical Sciences at Monash Health, Faculty of Medicine, Nursing and Health Sciences, Monash
Curr Osteoporos Rep
prevalence of obesity in older populations increasing, most fractures now occur in overweight and obese older adults [3], and so identifying risk factors within this population is important. This review summary provides a background on sarcopenia and sarcopenic obesity, together with the less wellestablished concepts of dynapenia and dynapenic obesity, their associations with fall and fracture risk, and the role of lifestyle interventions in preventing these outcomes.
Sarcopenia The term sarcopenia, from the Greek for Bpoverty of flesh^, was first proposed as a descriptor for age-related muscle wasting by Irwin Rosenberg in 1988 [4]. The first operational definition was provided by Baumgartner and colleagues in 1998, who defined sarcopenia as dual-energy X-ray absorptiometry (DXA)-determined appendicular lean mass (ALM; in kg)/height (m2) (ALM/Ht2) less than two standard deviations below the mean of a young adult reference group [5]. While this definition has been most commonly used to diagnose sarcopenia, definitions normalised for body weight, body fat, and BMI have also been proposed given that ALM/Ht2 may underestimate sarcopenia prevalence in obese individuals [6]. The resulting lack of standardisation and poor agreement between sarcopenia definitions has been recognised as a major barrier to determining prevalence and consequences of sarcopenia and its inclusion in routine clinical practice [7]. In order to address these issues, several expert groups have proposed consensus definitions including measurements and thresholds relevant to clinical settings [8–11]. For instance, the European Working Group on Sarcopenia for Older People (EWGSOP) defines sarcopenia as the presence of low muscle mass in addition to low muscle strength and/or gait speed [8]. Consensus definitions to date have been based on expert opinion, and the Foundation for the National Institutes of Health Biomarkers Consortium Sarcopenia Project is the first to provide evidence-based thresholds using muscle mass and hand grip strength data from nine international cohort studies [12•]. Although a single clinical definition of sarcopenia is not recognised globally, it is evident that most experts now view sarcopenia as a multidimensional condition involving agerelated declines in muscle mass, strength and function. However, in recent years, there has been support for considering muscle mass and strength declines as separate processes, and for the purposes of this review, sarcopenia will be defined as age-related loss of muscle mass only.
Dynapenia Longitudinal studies have disproved the concept that declines in muscle mass with age are the primary cause of muscle
strength and function deficits [13, 14]. The faster rate of decline in strength with age appears to be a result of declines in Bmuscle quality^ which may be attributable to age-related changes in neurologic and skeletal muscle factors including a loss of motor neurons, neuromuscular transmission, muscle fibre morphology, and adipose tissue infiltration between muscles and muscle fascicles (inter- and intra-muscular adipose tissue; IMAT) [15]. Furthermore, low muscle strength has been shown to be a stronger and more consistent predictor of functional decline, falls and mortality than low muscle mass [16]. In 2008, Clark and Manini suggested that loss of muscle strength and/or mechanical power, termed dynapenia (from the Greek for Bpoverty of strength^), should be considered a separate, and potentially more functionally relevant, condition than sarcopenia [17]. Clark and Manini subsequently proposed an algorithm for defining dynapenia including measurements of hand grip and knee extension strength, with subsequent investigations to determine neurological or muscular causation of dynapenia [18•]. However, currently, an operational definition of dynapenia does not exist and the term itself has not been widely adopted perhaps owing to the fact that strength and function remain incorporated in current sarcopenia definitions.
Sarcopenic and Dynapenic Obesity Low muscle mass relative to fat mass was first described as sarcopenic obesity by Heber and colleagues in 1996 [19]. Obesity is independently associated with poor physical function in older adults [20, 21] but may also contribute to systemic low-grade inflammation which can exacerbate muscle loss leading to sarcopenia. A synergistic effect may occur in which sarcopenia contributes to further gains in fat mass through a reduction in physical activity and resting energy expenditure [1]. Similar to research into sarcopenia itself, early studies of sarcopenic obesity focused on low muscle mass [22], but Stenholm and colleagues later proposed that the sarcopenic component should include an assessment of muscle strength, rather than muscle mass [23], and some research groups have now adopted the term dynapenic obesity to describe low muscle strength in obesity [24–27]. Currently, however, there is no consensus on the definition or diagnosis of sarcopenic or dynapenic obesity and these are urgently required if researchers are to provide comparable prevalence and outcome data and promote assessment of these conditions in the clinic. Indeed, prevalence estimates for sarcopenic obesity range from 4 to 94 % in National Health and Nutrition Examination Survey (NHANES) participants according to previously published definitions of sarcopenic obesity [28]. Table 1 provides a summary of potential operational definitions according to current consensus definitions of sarcopenia and research into sarcopenic obesity. It should be noted that Manini and
Curr Osteoporos Rep Table 1 Recommended measurements and thresholds for sarcopenia, dynapenia and obesity according to current consensus definitions for sarcopenia and sarcopenic obesity studies
Sarcopenia
Dynapenia
Obesity
ALM/Ht2: Men
NUTRITION, EXERCISE, AND LIFESTYLE IN OSTEOPOROSIS (CM WEAVER AND R DALY, SECTION EDITORS)
Fall and Fracture Risk in Sarcopenia and Dynapenia With and Without Obesity: the Role of Lifestyle Interventions David Scott 1,2 & Robin M. Daly 3 & Kerrie M. Sanders 2,4 & Peter R. Ebeling 1,2
# Springer Science+Business Media New York 2015
Abstract Due to their differing etiologies and consequences, it has been proposed that the term Bsarcopenia^ should revert to its original definition of age-related muscle mass declines, with a separate term, Bdynapenia^, describing muscle strength and function declines. There is increasing interest in the interactions of sarcopenia and dynapenia with obesity. Despite an apparent protective effect of obesity on fracture, increased adiposity may compromise bone health, and the presence of sarcopenia and/or dynapenia (Bsarcopenic obesity^ and Bdynapenic obesity^) may exacerbate the risk of falls and fracture in obese older adults. Weight loss interventions are likely to be beneficial for older adults with sarcopenic and dynapenic obesity but may result in further reductions in muscle and bone health. The addition of exercise including progressive resistance training and nutritional strategies, including protein and vitamin D supplementation, may optimise body composition and muscle function outcomes thereby reducing falls and fracture risk in this population.
Keywords Sarcopenia . Dynapenia . Obesity . Falls . Fractures . Lifestyle
Introduction Ageing is associated with progressive declines in the skeletal muscle mass and quality and concomitant increases in fat mass, which have significant metabolic and functional consequences [1]. Falls and fracture are a common concern for many older people, with low muscle mass (Bsarcopenia^) and muscle strength (Bdynapenia^) both implicated as risk factors for these outcomes. However, when combined with obesity (Bsarcopenic obesity^ or Bdynapenic obesity^), the associations are unclear due to a lack of prospective studies and controversy on the role of fat mass in falls and fracture risk [2]. Obese older people have higher fall risk than non-obese but may have reduced fracture risk due to greater bone strength and/or the protective effect of higher amounts of soft tissue. Nevertheless, with the
This article is part of the Topical Collection on Nutrition, Exercise, and Lifestyle in Osteoporosis * David Scott [email protected] Robin M. Daly [email protected] Kerrie M. Sanders [email protected]
Medical Centre, Monash University, 246 Clayton Road, Clayton, VIC, Australia 3168 2
Melbourne Medical School (Western Campus) and Australian Institute for Musculoskeletal Science, Sunshine Hospital, The University of Melbourne, 176 Furlong Road, St Albans, VIC, Australia 3021
3
Centre for Physical Activity and Nutrition Research, School of Exercise and Nutrition Sciences, Deakin University, 221 Burwood Highway, Burwood, VIC, Australia 3125
4
Institute for Health and Ageing, Australian Catholic University, Level 6, 215 Spring Street, Melbourne, VIC, Australia 3000
Peter R. Ebeling [email protected] 1
Department of Medicine, School of Clinical Sciences at Monash Health, Faculty of Medicine, Nursing and Health Sciences, Monash
Curr Osteoporos Rep
prevalence of obesity in older populations increasing, most fractures now occur in overweight and obese older adults [3], and so identifying risk factors within this population is important. This review summary provides a background on sarcopenia and sarcopenic obesity, together with the less wellestablished concepts of dynapenia and dynapenic obesity, their associations with fall and fracture risk, and the role of lifestyle interventions in preventing these outcomes.
Sarcopenia The term sarcopenia, from the Greek for Bpoverty of flesh^, was first proposed as a descriptor for age-related muscle wasting by Irwin Rosenberg in 1988 [4]. The first operational definition was provided by Baumgartner and colleagues in 1998, who defined sarcopenia as dual-energy X-ray absorptiometry (DXA)-determined appendicular lean mass (ALM; in kg)/height (m2) (ALM/Ht2) less than two standard deviations below the mean of a young adult reference group [5]. While this definition has been most commonly used to diagnose sarcopenia, definitions normalised for body weight, body fat, and BMI have also been proposed given that ALM/Ht2 may underestimate sarcopenia prevalence in obese individuals [6]. The resulting lack of standardisation and poor agreement between sarcopenia definitions has been recognised as a major barrier to determining prevalence and consequences of sarcopenia and its inclusion in routine clinical practice [7]. In order to address these issues, several expert groups have proposed consensus definitions including measurements and thresholds relevant to clinical settings [8–11]. For instance, the European Working Group on Sarcopenia for Older People (EWGSOP) defines sarcopenia as the presence of low muscle mass in addition to low muscle strength and/or gait speed [8]. Consensus definitions to date have been based on expert opinion, and the Foundation for the National Institutes of Health Biomarkers Consortium Sarcopenia Project is the first to provide evidence-based thresholds using muscle mass and hand grip strength data from nine international cohort studies [12•]. Although a single clinical definition of sarcopenia is not recognised globally, it is evident that most experts now view sarcopenia as a multidimensional condition involving agerelated declines in muscle mass, strength and function. However, in recent years, there has been support for considering muscle mass and strength declines as separate processes, and for the purposes of this review, sarcopenia will be defined as age-related loss of muscle mass only.
Dynapenia Longitudinal studies have disproved the concept that declines in muscle mass with age are the primary cause of muscle
strength and function deficits [13, 14]. The faster rate of decline in strength with age appears to be a result of declines in Bmuscle quality^ which may be attributable to age-related changes in neurologic and skeletal muscle factors including a loss of motor neurons, neuromuscular transmission, muscle fibre morphology, and adipose tissue infiltration between muscles and muscle fascicles (inter- and intra-muscular adipose tissue; IMAT) [15]. Furthermore, low muscle strength has been shown to be a stronger and more consistent predictor of functional decline, falls and mortality than low muscle mass [16]. In 2008, Clark and Manini suggested that loss of muscle strength and/or mechanical power, termed dynapenia (from the Greek for Bpoverty of strength^), should be considered a separate, and potentially more functionally relevant, condition than sarcopenia [17]. Clark and Manini subsequently proposed an algorithm for defining dynapenia including measurements of hand grip and knee extension strength, with subsequent investigations to determine neurological or muscular causation of dynapenia [18•]. However, currently, an operational definition of dynapenia does not exist and the term itself has not been widely adopted perhaps owing to the fact that strength and function remain incorporated in current sarcopenia definitions.
Sarcopenic and Dynapenic Obesity Low muscle mass relative to fat mass was first described as sarcopenic obesity by Heber and colleagues in 1996 [19]. Obesity is independently associated with poor physical function in older adults [20, 21] but may also contribute to systemic low-grade inflammation which can exacerbate muscle loss leading to sarcopenia. A synergistic effect may occur in which sarcopenia contributes to further gains in fat mass through a reduction in physical activity and resting energy expenditure [1]. Similar to research into sarcopenia itself, early studies of sarcopenic obesity focused on low muscle mass [22], but Stenholm and colleagues later proposed that the sarcopenic component should include an assessment of muscle strength, rather than muscle mass [23], and some research groups have now adopted the term dynapenic obesity to describe low muscle strength in obesity [24–27]. Currently, however, there is no consensus on the definition or diagnosis of sarcopenic or dynapenic obesity and these are urgently required if researchers are to provide comparable prevalence and outcome data and promote assessment of these conditions in the clinic. Indeed, prevalence estimates for sarcopenic obesity range from 4 to 94 % in National Health and Nutrition Examination Survey (NHANES) participants according to previously published definitions of sarcopenic obesity [28]. Table 1 provides a summary of potential operational definitions according to current consensus definitions of sarcopenia and research into sarcopenic obesity. It should be noted that Manini and
Curr Osteoporos Rep Table 1 Recommended measurements and thresholds for sarcopenia, dynapenia and obesity according to current consensus definitions for sarcopenia and sarcopenic obesity studies
Sarcopenia
Dynapenia
Obesity
ALM/Ht2: Men
