Muscle Strength Is Independently Related to Brain Atrophy in Patients with Alzheimer's Disease

Background/Aims: Alzheimer's disease (AD) is the most common cause of dementia worldwide. Interestingly, muscle mass (MM) and muscle strength (MS) are related to AD. In addition to the muscle profile, brain atrophy is also a prominent feature of AD. There is substantial evidence showing an association between muscle profile and dementia, but the role of the muscle profile and cerebral cortical atrophy within this association is less well understood. The objective of this study was to determine if there is any association between muscle profile and brain regional volume in AD. A secondary objective was to determine whether this relationship continues as the clinical stage of AD progresses. Methods: We recruited 28 patients with probable AD without weakness. We assessed the patients' basic demographic characteristics, Mini-Mental State Examination score, and brain magnetic resonance images. MM was measured using body dual-energy X-ray absorptiometry. MS was assessed in Nm/kg with an isokinetic knee extensor using an isokinetic device at an angular velocity of 60 degrees/s. An automatic analysis program was used for brain regional volumetric measurements. Dementia was divided into two stages: mild and moderate. Results: MS was related to left hippocampal volume ratio. After adjusting for age and cognitive status, the relationship remained. MS did not demonstrate any relationship to any brain regional volume ratio in the mild stage; however, in the moderate stage, it was positively related to both the right and the left hippocampal volume ratio. Conclusions: Our findings imply a shared underlying pathology relating MS and brain volume and suggest cognitive functional declines through the muscle-brain axis. Further longitudinal studies are needed to find possible and related causes of reduced MS and cortical atrophy in patients with dementia.