The European Working Group on Sarcopenia in Older People (EWGSOP) defines sarcopenia as "a syndrome characterised by progressive and generalised loss of skeletal muscle mass and strength, with a risk of adverse outcomes such as physical disability, poor quality of life and high mortality."
Many people get sarcopenia, although it is rarely formally diagnosed. There is a push to get doctors to recognize this syndrome.
The medical tests DXA and BIA - bioelectrical empirical analysis - can help doctors diagnose sarcopenia.
The following measurements suggest sarcopenia:
Walking speed under 0.8 m/sec
BIA readings of lean body mass:
men - less than 8.50 kg/m^2
Women - less than 5.75 kg/m^2
DXA of course is dual-energy X-ray absorptiometry used to measure bone density in common checks for osteoporosis. Here it is used to estimate body mass in limbs. ALMH is a parameter analogous to BMI but for limbs rather than for the whole body. Appendicular lean mass (ALM)/height^2)
Sarcopenia is suggested if DXA - ALMH
men - less than 7.26 kg/m^2
Women - less than 5.45 kg/m^2
Osteosarcopenia isn’t a disease; it’s a syndrome. (A syndrome is a cluster of symptoms and signs, which may or may not be due to one or more diseases.) Osteopenia is low bone density, and sarcopenia is loss of muscle mass and strength. When people get them both, the resulting impact on the quality of life can be worse than either one produces by itself. The syndrome produces falls, fractures, and disability and increases the probability of death This syndrome affects the elderly, but the prevalence is unknown partly because only recently has it been recognized.
The causes are unknown, too, and it is probably true that there are multiple causes in any individual and osteosarcopenia in one individual may be due to different factors than osteosarcopenia in another person. Genetic factors could be partly responsible as well as lifestyle (activity, exercise), other co-morbid conditions, and medications taken.
Bone and muscle closely interact with each other, Fat infiltration of bone tissue happens often when elderly people lose bone mass and muscle tissue. A better understanding of how muscle and bone interact with each other may lead to effective therapies.
With no definitive cause the treatments at this point are pragmatic and common sense: exercise and nutrition. Perhaps in the future pharmacological therapies will be developed. SARMs may be a treatment for osteosarcopenia some day.