Sarcopenia

Keywords Constipation Peptic ulcers Dryness of the mouth Renal failure Urinary incontinence Osteoporosis Sarcopenia Orthostatic hypotension Vertigo... 

As we grow older our muscle strength diminishes and the risk of developing sarcopenia increases. The meaning of the word sarcopenia is an abnormal decline in muscle strength and mass. Another word is muscle atrophy. Between early middle age and older age the mean decrease is 50% of muscle mass. Another way to calculate the loss of muscle mass is that over 50 years of age 1-2% of muscle tissue mass vanishes yearly. Between 50 and 70 years of age almost 15% of muscle strength per 10 years disappears. The resulting disability in older persons with sarcopenia has been calculated to cost approximately 900 dollars per person and year. The yearly total of healthcare expenditures for sarcopenia in the United States is estimated at 18-20 billions (Janssen et al. 2004). 

The concept of sarcopenia is not as well known as osteoporosis, which is the equivalent in bone tissue loss. Even though an older patient has not lost weight, sarcopenia can still be present because of an increased amount of fat tissue. It is important to check the patients for muscle strength as this is a condition which we are able to treat successfully if discovered in time. There are several other reasons for loss of muscle strength in the elderly, such as sickness, inactivity and poor nutrition (Doherty 2003). 

There is no other way to diminish the effects of sarcopenia but to maintain and increase physical activities and it is vital to keep a good nutritional strategy, especially in old age (Binder et al. 2005, Ades et al. 1996, Evans 1995). The way to be successful in this is to take up these habits early in life and be aware of the risks of inactivity. 

The normal course in aging is loss of muscle tissue and strength, sarcopenia... 

Davis LE (1994) Dizziness in elderly men. 1 Am Geriatr Soc 42(11) 1184-1188 Doherty T (2003) Invited review Aging and sarcopenia. 1 Appl Physiol 95(4) 1717-1727 Dutta C (1997) Significance of sarcopenia in the elderly. J Nutr 127(5 Suppl) 992S-993S Evans WJ (1995) Effects of exercise on body composition and functional capacity of the elderly. 

A decrease in muscle mass occurs normally during ageing (known as sarcopenia) and decreases resting energy expenditure so that less food is required. 

Muhlberg, W. and Sieber, C. (2004) Sarcopenia and frailty in geriatric patients implications for training and prevention. Zeitschrifi fur Gerontologie und Geriatrie, 37, 2-8. 

Lynch, G.S. (2004) Emerging drugs for sarcopenia age-related muscle wasting. Expert Opinion on Emerging Drugs, 9, 345-361. 

Sarcopenia is defined as an involuntary loss of skeletal muscle mass and function that occnrs with advancing age. It has been associated with muscle weakness resulting in an increased prevalence of falls, loss of function and independence, and higher morbidity. As the elderly population increases, sarcopenia and its resulting disability will become increasingly important. There are 39 million Americans over the age of 65, with an expected increase of 6 million in the next 10 years. 

Bhasin S. Testosterone supplementation for aging-associated sarcopenia. J Gerontol A Biol Sci Med Sci 2003 58 1002-1008. 

Paddon-Jones D, Rasmussen BB. Dietary protein recommendations and the prevention of sarcopenia. Curr Opin Clin Nutr Metab Care. 2009 12(l) 86-90. 

Electrical impedance myography (EIM) refers to a group of impedance-based methods for the clinical assessment of muscles. This includes primary disorders of muscle such as myopathic conditions (Rutkove et al., 2002 Tarulli et al., 2005) and the sarcopenia of aging (Aaron et al., 2006) as well as diseases that affect the nerve, such as localized... 

Nedergaard, A., M. A. Karsdal, S. Sun, and K. Henriksen (2013). Serological muscle loss biomarkers an overview of current concepts and future possibilities. J Cachexia Sarcopenia Muscle Aiiy. 1-17. 

Note that we use AAM instead of the term sarco-penia. "Sarcopenia" sounds like a definitive diagnosis but it is not. It is often erroneously interpreted as designating a singular pathogenesis. Sarcopenia simply refers, imprecisely, to muscle atrophy in aged animals it does not indicate or imply any pathogenic mechanism, of which there are a number of possibilities. AAM is usually manifest as type-2 fiber atrophy. A further critique of "sarcopenia" is presented below. 

So-called "sarcopenia" seems more neuropathic than purely myopathic... 

If, as we postulate, there is a significant neuropathic component in "sarcopenia," analyses of homogenized muscle are actually looking only at the train wreck but not seeking the upstream cause of the derailment. If a denervation/dysinnervation component is indeed present, that would require moving the focus of pathogenic interest and analysis upstream to the LMNs, their Schwann cells, and possibly to their pre-synaptic afferent neurons. 

Cruz-Jentoft AJ, Baeyens JP, Bauer JM et al. (2010) Sarcopenia European consensus on definition and diagnosis Report of the European Working Group on Sarcopenia in Older People. Age Ageing 39, 412-A23. 

Kung T, Springer J, Doehner W et al. (2010) Novel treatment approaches to cachexia and sarcopenia highlights from the 5th Cachexia Conference. Expert Opin Investig Drugs 19, 579-585. 

Waters DL, Baumgartner RN, Garry PJ et al. (2010) Advantages of dietary, exercise-related, and therapeutic interventions to prevent and treat sarcopenia... 

D Antona G, Nisoli B. (2010) mTOR signaling as a target of amino acid treatment of the age-related sarcopenia. Interdiscip Top Gerontol 37, 115-141. 

Let us turn the title of this chapter on its head and consider first the clinical consequences of aging on muscle sarcopenia, a Greek term that simply means "muscle atrophy"), then the theoretical and experimental evidence of mitochondrial involvement in the aging process, and finally the therapeutic measures that can be adopted, if not to prevent, then at least to delay and contain the inevitable occurrence of sarcopenia. 

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