Sarcopenia, cachexia and frailty in older cats: Mechanisms, assessment and therapeutic considerations

PRACTICAL RELEVANCE: Age-related muscle loss due to sarcopenia and cachexia is common in mammals and is likely a major contributor to frailty in older cats. Frailty adversely affects quality of life and is a predictor of survival time. In some cats, excess body fat is preserved but muscle mass is lost, a condition termed sarcopenic obesity. Although the mechanisms underlying sarcopenia and cachexia have been studied in humans, the pathophysiology has not been well studied in cats. CLINICAL CHALLENGES: Early diagnosis of muscle loss by a muscle condition score may aid therapeutic intervention, and epaxial muscle ultrasound offers a promising adjunctive diagnostic tool. In humans, muscle strength predicts adverse outcomes; however, direct measurement of this is difficult in cats. Furthermore, in humans, physical performance is used as an estimate of muscle strength; in cats, it may be possible to estimate strength and function by activity. The development and use of a frailty score, which incorporates activity along with other measurements, will provide a valuable tool, which may improve the assessment of the effects of sarcopenia in cats, including their quality of life and possibly survival time.Therapeutic considerations:Anabolic resistance to muscle synthesis may result in increased dietary protein requirements. Some older cats may also have decreased fat and protein digestion, sometimes concurrently with decreased serum cobalamin and vitamin E. These nutritional requirements should be addressed along with feeding management practices.Recent advances and future prospects:New therapeutic interventions for sarcopenia are being investigated for humans, often in conjunction with resistance exercise; however, their safety and efficacy have not been evaluated in cats. Further research in this area presents an opportunity to improve the health and longevity of ageing cats. AIMS: The aim of this review is to describe the pathophysiology, diagnosis and potential treatment of feline muscle loss. Further aims are to encourage early diagnosis and treatment of muscle loss by clinicians and to inspire more research in this area.