Background: Population aging has resulted in an increase in age-related conditions. Sarcopenia, the progressive loss of muscle mass and strength, and frailty, vulnerability to poor resolution of homeostasis after a stressor, are common causes of functional decline in older individuals. There is a paucity of work on how they interrelate with dementia. The objective of this review was to examine the literature on sarcopenia and frailty in dementia.

Methods and results: Studies of sarcopenia and frailty in dementia were searched for in EMBASE, PubMed and Web of Science, and via hand-searching. Citations were screened for independently by two reviewers, with disagreements resolved by a third reviewer. To be eligible for inclusion, the articles needed to fulfil: (1) English language; (2) human studies; and (3) full-text available. Dementia of any aetiology was included. 303 non-duplicate recorders were identified, of which 270 irrelevant papers were excluded. Of the remaining 33, 27 examined frailty and 13 sarcopenia, with six of these measuring both. An increased prevalence of frailty and sarcopenia was noted in dementia patients. However, nine papers did not specify dementia aetiologies. Of those that did (n = 21), 20 examined Alzheimer's disease, with three also including Lewy body dementia, three vascular dementia, and one Parkinson's disease dementia.

Conclusion: Most papers examined frailty, rather than sarcopenia, in dementia. The studies were heterogeneous, using different protocols and non-validated definitions. However, dementia patients may have an increased prevalence of frailty and sarcopenia. This review highlights key gaps in accurate diagnosis of frailty/sarcopenia and in non-Alzheimer's dementia.