Year: 2026
Type: dissertation
Abstract: Background: Sarcopenia, characterised by decreased muscle mass and muscle function, and obesity (excessive fat mass) have been linked to negative health outcomes and brain health. The coexistence of sarcopenia and obesity, called sarcopenic obesity (SO), may have a synergistic or additive negative impact on cognition. Sarcopenia, obesity, and cognitive impairment are prevalent conditions among older individuals. The definitions of SO remain inconsistent across studies. Aim: The main aim of this thesis was to review and investigate the association between SO, cognitive impairment and dementia risk. Methods: This thesis contains 4 main chapters, including a narrative review (Chapter 2), a systematic review and meta-analysis of longitudinal studies (Chapter 3), and two analyses based on observational data from the National Health and Nutrition Examination Survey (NHANES) (Chapters 4 and 5). In Chapter 4, SO phenotypes were created based on several definitions and cutoffs (high adiposity-low muscle mass (HA-LM), high fat mass-fat free mass ratio (FM/FFM), high trunk fat mass-appendicular skeletal muscle mass ratio (TrFM/ASM), and high waist circumference-low hand grip strength (WC-HGS)) to investigate the association between SO and cognitive impairment (low neuropsychological tests scores) in older adults. In Chapter 5, the new SO definition (screening: sign of sarcopenia (high SARC-F score) with high body mass index (BMI) and/or high WC; diagnostic phase I: added low muscle strength; diagnostic phase II: added low muscle mass and high fat mass) implemented by the European Society for Clinical Nutrition and Metabolism and the European Association for the Study of Obesity (ESPEN-EASO) was used to investigate its association with cognitive impairment (low digit symbol substitution test (DSST) score) in middle-aged and older adults. Results: The findings from the narrative review revealed the complex link between SO and brain function deterioration. The interrelated mechanisms that may be involved include impaired muscle glucose metabolism, reduced secretion of neuroprotective myokines, negatively impacted cerebral blood flow, obesity-related insulin resistance, oxidative stress, and neuroinflammation, all contributing to impaired brain signalling, memory loss, and cognitive impairment. The systematic review and meta-analysis revealed a positive association between SO and all-cause dementia (ACD) risk, with no studies on Alzheimer’s Disease (AD) and vascular dementia (VaD). Sarcopenia itself showed a positive association with ACD, AD and VaD, whereas obesity was associated with an increased risk of AD and VaD, but not with ACD. In Chapter 4, the findings support the positive association between low DSST scores and SO using FM/FFM (OR 2.0, CI 95% 1.3–3.1) and WC-HGS (OR 2.5, CI 95% 1.6–4.0) models in individuals aged 60-85 years. In Chapter 5, the new ESPEN-EASO SO phenotypes were associated with lower DSST scores at diagnostic phase I (OR 2.3, CI 95% 1.4–3.8) and phase II (OR 2.7, CI 95% 1.5–4.9) in individuals aged 60-85 years. Conclusions: SO was associated with cognitive impairment and dementia risk. The nature of this association may vary based on the definitions of SO used. The updated ESPEN-EASO definition of SO should be adopted in future research. Furthermore, the interrelated mechanisms linking SO to cognitive impairment warrant further investigation through clinical and epidemiological studies to inform the design of effective prevention strategies.
Author: Booranasuksakul, Uraiporn
Language: English
Subfield: Physiology (medical)
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W7217584407