Morley JE. Frailty and sarcopenia: the new geriatric giants. Rev Investig Clin. 2016; 68(2):59–67.45 45. Cruz‐Jentoft AJ, Sayer AA. Sarcopenia. Lancet. 2019; 393(10191):2636–2646.
46 46. Dent E, Lien C, Lim WS, et al. The Asia‐Pacific clinical practice guidelines for the management of frailty. J Am Med Dir Assoc. 2017; 18(7):564–575.
47 47. Dent E, Morley JE, Cruz‐Jentoft AJ, et al. Physical frailty: ICFSR international clinical practice guidelines for identification and management. J Nutr Health Aging. 2019; 23(9):771–787.
48 48. Ram CVS, Giles TD. The evolving definition of systemic arterial hypertension. Curr Atheroscler Rep. 2010; 12(3):155–158.
49 49. Słodki M, Respondek‐Liberska M, Pruetz JD, Donofrio MT. Fetal cardiology: changing the definition of critical heart disease in the newborn. J Perinatol. 2016; 36(8):575–580.
50 50. Louis ED. The evolving definition of essential tremor: what are we dealing with? Parkinsonism Relat Disord. 2018; 46(Suppl 1):S87–S91.
51 51. Beaudart C, Rolland Y, Cruz‐Jentoft AJ, et al. Assessment of muscle function and physical performance in daily clinical practice: a position paper endorsed by the European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO). Calcif Tissue Int. 2019; 105(1):1–14.
52 52. Malmstrom TK, Miller DK, Simonsick EM, Ferrucci L, Morley JE. SARC‐F: a symptom score to predict persons with sarcopenia at risk for poor functional outcomes. J Cachexia Sarcopenia Muscle. 2016; 7(1):28–36.
CHAPTER 2 Epidemiology of Muscle Mass Loss with Age
Marjolein Visser
Department of Health Sciences, Faculty of Science, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
INTRODUCTION
The development of new body composition methods in the early 1970s and 1980s led to more research on this topic, including the study of differences in body composition between young and older persons. These initial studies were followed by much larger studies covering a wide age range investigating how body composition varied across the life span. Variations in lean body mass and fat‐free mass were described between age groups. These studies served as the important scientific basis for developing the concept sarcopenia. Sarcopenia was originally defined as the age‐related loss of muscle mass [1]. The term is derived from the Greek words sarx (flesh) and penia (loss). The development of this concept further stimulated research in this specific body composition area. More recently, large‐scale studies among older persons have included accurate and precise measurements of skeletal muscle mass. Moreover, these measurements have been repeated over time, enabling the sarcopenia process to be studied.
This chapter will discuss the results of epidemiological studies investigating the age‐related loss of skeletal muscle mass. First, several cross‐sectional studies will be presented comparing the body composition between younger and older persons. Then prospective studies will be discussed investigating the change in body composition with aging. The chapter will conclude with the results of more recent, prospective studies that precisely measured change in skeletal muscle mass in large samples of older persons.
MUSCLE MASS DIFFERENCES AMONG AGE GROUPS
Comparisons among young and older men and women with regard to muscle size have been made in several small studies starting in the 1980s. The results showed that healthy women in their 70s had a 33% smaller quadriceps cross‐sectional area as obtained by compound ultrasound imaging compared with women in their 20s [2]. Using the same methodology and age groups, healthy older men had a 25% smaller quadriceps cross‐sectional area [3]. In a study investigating thigh composition using five computed tomography (CT) scans of the total thigh, smaller muscle cross‐sectional areas were observed in older men compared with younger men even though their total thigh cross‐sectional area was similar. The older men had a 13% smaller total muscle cross‐sectional area, 25.4% smaller quadriceps, and 17.9% smaller hamstring cross‐sectional area [4]. Using magnetic resonance imaging of the leg anterior compartment, muscle area was measured in young and older men and women [5]. The older persons had a smaller area of contractile tissue, 11.5% less in women and 19.2% less in men, compared with the young persons. These data, obtained by different body composition technologies, clearly showed a smaller muscle size in older persons compared with young persons. The observed differences in muscle size between age 20 and age 70 suggested a loss of skeletal muscle mass of about 0.26–0.56% per year.
Figure 2.1 Differences in fat‐free mass and lean mass using different body composition methodologies between men of different age groups. BIA = bioelectrical impedance; DXA = dual‐energy x‐ray absorptiometry.
Source: Based on references [7, 8].
The amount of non‐muscle tissue within the muscle was also assessed using five CT scans of the thigh in 11 older men and 13 young men [4]. Older men had 59.4% more non‐muscle tissue within the quadriceps and 127.3% within the hamstring muscle. In a similar study, the amount of non‐muscle tissue in older men was 81% higher in the plantar flexors as compared with young men [6]. Thus, apart from the smaller muscle size in old age, these studies suggested that the composition of the muscle also changed with aging, leading to less “lean” muscle tissue in old age.
With the greater availability of body composition methods such as bioelectrical impedance and dual‐energy x‐ray absorptiometry (DXA) over time, cross‐sectional data on muscle size in large study samples including a broad age range have been collected. Examples of these studies using lean mass from DXA (the non‐bone, non‐fat soft tissue mass) and fat‐free mass from bioelectrical impedance, presented by 10‐year age groups of men, are presented in Figure 2.1 [7, 8]. Older age groups had a lower total body fat‐free mass, lower total body lean mass, and lower arm and leg lean mass. Figure 2.2 presents the differences in muscle size between 10‐year age groups in men and women. With increasing age group, the data suggested a lower whole‐body lean mass and leg lean mass as assessed by DXA [9], a smaller arm muscle cross‐sectional area (from anthropometric measures [10]), and a smaller calf muscle cross‐sectional area (from peripheral qualitative CT [11]). These cross‐sectional data derived from samples from Italy, Australia, India, Japan, and the United States consistently suggested a decline in muscle size with aging. These data also suggested a steeper decline in muscle size with aging in men compared with women.
Figure 2.2 Differences in muscle cross‐sectional area and lean mass using different body composition methodologies between men and women of different age groups. DXA = dual‐energy x‐ray absorptiometry; CT = computed tomography; Anthrop. = anthropometry, using arm circumference and triceps skinfold.
Source:
