Sarcopenic obesity is associated with cognitive impairment in community-dwelling older adults: The Bunkyo Health Study

Association of muscle mass, grip strength and fat-to-muscle ratio and metabolic dysfunction-associated steatotic liver disease in a middle-to-elderly aged population

OBJECTIVE

The association of appendicular skeletal muscle mass (ASM), grip strength and fat-to-muscle ratio (FMR) and the progression of metabolic dysfunction-associated steatotic liver disease (MASLD) are not well known.

MATERIALS AND METHODS

This study included participants older than 40 years who underwent bioelectrical impedance assessment in Prevalence of Metabolic Diseases and Risk Factors in Shunde (SPEED-Shunde). We measured grip strength with an electronic grip strength metre. ASM and grip strength were adjusted by dividing body mass index (BMI). FMR was calculated as total fat mass to total muscle mass. Liver steatosis and liver fibrosis were evaluated by vibration-controlled transient elastography. Multifactorial logistic regression was used to analyse the relationship between ASM, grip strength, FMR, and MASLD or MASLD-associated liver fibrosis. We performed subgroup analyses according to sex, age and BMI. Interaction tests and linear trend tests were also conducted.

RESULTS

This study included a total of 3277 participants. FMR was positively associated with MASLD (OR: 1.89, 95% CI: 1.66-2.15) and MASLD-associated liver fibrosis (OR: 1.70, 95% CI: 1.22-2.37). While ASM/BMI (OR: 0.59, 95% CI: 0.52-0.67) or grip strength/BMI (OR: 0.72, 95% CI: 0.66-0.78) were negatively associated with MASLD. Interactions were observed between ASM/BMI and age, grip strength and sex in MASLD, as well as FMR and MASLD-associated liver fibrosis.

CONCLUSION

In a middle-to-elderly aged population, FMR was positively associated with the risk of MASLD and MASLD-associated liver fibrosis, and muscle mass and grip strength were negatively associated with MASLD, rather than MASLD-associated liver fibrosis.

Detecting sarcopenia in obesity: emerging new approaches

PURPOSE OF REVIEW

Sarcopenic obesity is a likely common, but certainly underestimated obesity phenotype, with an important negative clinical impact. Its definition and diagnosis have however remained elusive until recently.

RECENT FINDINGS

Substantial progress has been recently made in sarcopenic obesity diagnostic tools, with the first international consensus proposed by the European Society for Clinical Nutrition and Metabolism (ESPEN) and the European Association for the Study of Obesity (EASO). Very encouraging results emerge from initial implementation of the ESPEN-EASO algorithm. In addition, even more recent progress in global consensus on sarcopenia conceptual definition is likely to further enhance consistency in sarcopenic obesity identification. The latter Global Leadership Initiative on Sarcopenia (GLIS) initiative also adopted a new definition of muscle specific strength. Its inclusion in sarcopenia diagnostic constructs opens the possibility of its potential evaluation in sarcopenic obesity, also considering the emerging positive impact of obesity treatment and fat loss on muscle functional parameters.

SUMMARY

New consensus tools for sarcopenic obesity diagnosis are likely to improve awareness, understanding, identification and treatment of this under-recognized obesity phenotype.

Meta-analysis on the interrelationship between sarcopenia and mild cognitive impairment, Alzheimer's disease and other forms of dementia

Sarcopenia has been associated with adverse health outcomes, including cognitive dysfunction. However, its specific interrelationship with neurocognitive disorders such as mild cognitive impairment (MCI), Alzheimer's disease (AD) or other types of dementia has not been thoroughly explored. This meta-analysis aims to summarize the existing evidence on this interrelationship. This systematic review was pre-registered on PROSPERO (CRD42022366309) and reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines. Databases, including PubMed, Embase, CINAHL, Scopus, Web of Science, PEDro, SPORTDiscus and the Cochrane Central Register of Controlled Trials, and the data registry ClinicalTrials.gov were searched from inception to 8 June 2023. Observational studies (cross-sectional and cohort) and interventional studies reporting on the association and prevalence of sarcopenia in MCI, AD or other types of dementia in adults ≥50 years were included. For the meta-analysis, pooled odds ratios (OR) with 95% confidence intervals (CI) were calculated for the association of sarcopenia with the neurocognitive disorders using random-effects/fixed-effects models. Subgroup analyses were performed to identify potential sources of heterogeneity. A total of 77 studies consisting of 92 058 subjects were finally included in the qualitative analysis (71 cross-sectional, 4 cohort and 2 interventional studies). Studies were heterogeneous, using different diagnostic criteria to define both sarcopenia and cognitive status. The majority of studies (n = 38) included Asian community-dwelling older adults. Most studies investigated the association of sarcopenia with AD (33/77) and MCI (32/77). For studies focusing on other forms of dementia, two studies included Lewy body dementia and one study included Parkinson's dementia, whereas the remaining studies did not specify dementia aetiology (n = 21). Three cohort studies explored the association between sarcopenia and incident MCI, whereas only one cohort study explored the association between dementia and incident sarcopenia. Two interventional studies investigated whether an exercise programme could prevent the progression of sarcopenia in older adults with dementia or AD. The information for the meta-analysis was extracted from 26 studies. Sarcopenia was significantly associated with MCI (pooled OR = 1.58, 95% CI 1.42-1.76) (n = 14), AD (pooled OR = 2.97, 95% CI 2.15-4.08) (n = 3) and non-AD dementia (pooled OR = 1.68, 95% CI 1.09-2.58) (n = 9). The significance and magnitude of the associations differed in subgroup analyses by study design, population, definition of sarcopenia or used tool to measure cognitive status. This meta-analysis showed that sarcopenia is significantly associated with MCI, AD and other types of dementia. These findings suggest the importance of early screening and prevention of sarcopenia in older people with cognitive dysfunction, although further longitudinal research is needed to clarify the causal relationship.

Body Composition, Sarcopenic Obesity, and Cognitive Function in Older Adults: Findings From the National Health and Nutrition Examination Survey (NHANES) 1999-2002 and 2011-2014

OBJECTIVE

Sarcopenic-obesity (SO) is characterized by the concomitant presence of low muscle mass and high adiposity. This study explores the association of body composition and SO phenotypes with cognitive function in older adults.

METHODS

Cross-sectional data in older adults (≥60 years) from NHANES 1999-2002 and 2011-2014 were used. In the 1999-2002 cohort, phenotypes were derived from body mass index (BMI) and dual-X-ray-absorptiometry, and cognition was assessed the by Digit-Symbol-Substitution-Test (DSST). In the 2011-2014 cohort, phenotypes were derived from BMI, waist-circumference (WC), and hand-grip-strength (HGS). Cognition was assessed using four tests: DSST, Animal Fluency, the Consortium-to-Establish-a-Registry-for-Alzheimer's-Disease-Delayed-Recall, and Word Learning. Mediation analysis was conducted to evaluate the contribution of inflammation (C-reactive-protein, CRP) and insulin resistance (Homeostatic-Model-Assessment-for-Insulin-Resistance, HOMA-IR) to the association between body composition and cognitive outcomes.

RESULTS

The SO phenotype had the lowest DSST mean scores (p < 0.05) and was associated with a significant risk of cognitive impairment [Odds Ratio (OR) = 1.9; 95%CI 1.0-3.7, p = 0.027] in the 1999-2002 cohort. A higher ratio of fat mass and fat free mass (FM/FFM) also showed a greater risk of cognitive impairment (OR = 2.0; 95%CI 1.3-3.1, p = 0.004). In the 2011-2014 cohort, the high WC-Low HGS group showed significantly lower scores on all four cognitive tests (p < 0.05) and a higher risk of cognitive impairment. CRP and HOMA-IR were significant partial mediators of the association between FM/FFM and DSST in the 1999-2002 cohort.

CONCLUSIONS

The SO phenotype was associated with a higher risk of cognitive impairment in older adults. Insulin resistance and inflammation may represent key mechanisms linking SO to the development of cognitive impairment.

Age, sex, and APOE gene-specific associations between dynapenic obesity and dementia in a large cohort

OBJECTIVE

To investigate the associations between dynapenic obesity and the risk of dementia, and the modifying effects of age, sex, and the APOE gene, using a large population-based cohort.

METHODS

279,884 participants aged 55 and above from the UK Biobank were included. The participants were classified into four categories based on body mass index and hand grip strength: healthy, obesity, dynapenia, and dynapenic obesity. The incident dementia was identified based on linked hospital records and death register data. Cox proportional hazards regression models were used to estimate the associations, followed by age-, sex-, and apolipoprotein E (APOE) gene-stratified analyses.

RESULTS

During the median follow-up of 12.4 years, 5,170 (1.8%) participants developed dementia. Compared with the healthy group, participants with dynapenic obesity had 67% higher dementia risk (hazard ratio [HR]: 1.67, 95% confidence interval [CI]: 1.44-1.94). Compared with the healthy group, higher risks of dementia in participants with dynapenic obesity were respectively observed in male (HR: 2.03, 95% CI: 1.65-2.50), younger (<65 years, HR: 1.97, 95% CI: 1.55-2.50), and non-ε4-carrier (HR: 1.97, 95% CI: 1.60-2.44) (all P for interaction <0.05). In participants under 65 years and non-ε4-carrier, those with dynapenic obesity had the highest risk of dementia (HR: 2.63, 95% CI: 1.91-3.62), compared with the healthy group (P for second order interaction = 0.026).

CONCLUSIONS

Dynapenic obesity is associated with increased risks of dementia, especially in participants under 65 years and non-ε4-carrier, suggesting the importance of managing dynapenic obesity in the prevention of cognition-related disorders.

Association Between Mid-arm Muscle Circumference and Cognitive Function: A Longitudinal Study of Chinese Adults

BACKGROUND

Dementia affects 55 million people worldwide and low muscle mass may be associated with cognitive decline. Mid-arm muscle circumference (MAMC) correlates with dual-energy Xray absorptiometry and bioelectrical impedance analyses, yet are not routinely available. Therefore, we examined the association between MAMC and cognitive performance in older adults.

METHODS

We included community-dwelling adults ≥55 years from the China Health and Nutrition Survey. Cognitive function was estimated based on a subset of the modified Telephone Interview for Cognitive Status (0-27, low-high) during years (1991, 1993, 1997, 2000, 2004, 2006, 2009, 2011, 2015, 2018). A multivariable linear mixed-effects model was used to test whether MAMC was associated with rate of cognitive decline across age groups and cognitive function overall.

RESULTS

Of 3702 adults (53% female, 63.2 ± 7.3 years), mean MAMC was 21.4 cm ± 3.0 and baseline cognitive score was 13.6 points ±6.6. We found no evidence that the age-related rate of cognitive decline differed by MAMC (P = .77). Declines between 5-year age groups ranged from -.80 [SE (standard error) .18] to -1.09 [.22] for those at a mean MAMC, as compared to -.86 [.25] to -1.24 [.31] for those at a 1 MAMC 1 standard deviation above the mean. Higher MAMC was associated with better cognitive function with .13 [.06] higher scores for each corresponding 1 standard deviation increase in MAMC across all ages.

CONCLUSION

Higher MAMC at any age was associated with better cognitive performance in older adults. Understanding the relationship between muscle mass and cognition may identify at-risk subgroups needing targeted interventions to preserve cognition.

The role of dynapenia and obesity on cognitive function in older adults

BACKGROUND & AIMS

Dynapenia and obesity have been independently associated with cognitive decline in older adults, but their co-occurring effects has not been well-studied. The study objective is to examine the relationship between dynapenic-obesity and cognitive impairment in older adults 75 years and older with normal or high cognitive function at baseline over 12 years of follow-up. We hypothesize that those with dynapenic obesity will have greater odds of cognitive function impairment than those with dynapenia only, obesity only, or no dynapenia no obesity (reference group).

METHODS

A total of 761 participants with a mean age of 81.5 and Mini-Mental State Examination (MMSE) > 21 at baseline were divided into four groups: no dynapenia no obesity (n = 316), obesity only (n = 142), dynapenia only (n = 217), and dynapenic obesity (n = 86). Measures included socio-demographics, medical conditions, body mass index, depressive symptoms, handgrip strength, and limitations in activities of daily living. We performed a mixed models estimate for cognitive decline for these groups over a 12-year period. Handgrip strength (HGS) was measured with a handgrip dynamometer and cognitive function was assessed with MMSE.

RESULTS

Participants in the dynapenia-obesity group experienced a greater (β = - 1.29, Standard Error = 0.60, p-value = 0.0316) cognitive decline over time compared to those in the no dynapenia and no obesity group, after controlling for all covariates.

CONCLUSION

Older adults with dynapenic-obesity were at high risk of cognitive decline over time. These findings highlight the need for interventions that target both conditions in this population to help maintain cognitive health. Community-based strength training programs and educational initiatives on nutrition and diet can help older adults reduce their risk of age-related cognitive decline.

Air pollution accelerates the development of obesity and Alzheimer's disease: the role of leptin and inflammation - a mini-review

Air pollution is an urgent concern linked to numerous health problems in low- and middle-income countries, where 92% of air pollution-related deaths occur. Particulate matter 2.5 (PM2.5) is the most harmful component of air pollutants, increasing inflammation and changing gut microbiota, favoring obesity, type 2 diabetes, and Alzheimer's Disease (AD). PM2.5 contains lipopolysaccharides (LPS), which can activate the Toll-like receptor 4 (TLR4) signaling pathway. This pathway can lead to the release of pro-inflammatory markers, including interleukins, and suppressor of cytokine signaling-3 (SOCS3), which inhibits leptin action, a hormone that keeps the energy homeostasis. Leptin plays a role in preventing amyloid plaque deposition and hyperphosphorylation of tau-protein (p-tau), mechanisms involved in the neurodegeneration in AD. Approximately 50 million people worldwide are affected by dementia, with a significant proportion living in low-and middle-income countries. This number is expected to triple by 2050. This mini-review focuses on the potential impact of PM2.5 exposure on the TLR4 signaling pathway, its contribution to leptin resistance, and dysbiosis that exacerbates the link between obesity and AD.

Low subcutaneous adipose tissue and myosteatosis are prognostic factors after allogeneic hematopoietic stem cell transplantation

OBJECTIVE

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) represents the only curative treatment option for several hematological neoplasms. This study aimed to assess the parameters of body composition as predictors of post-transplant overall survival (OS) and adverse events in patients with leukemia, myelodysplastic syndromes (MDS), and myeloproliferative neoplasms (MPN).

METHODS

This was a retrospective study of 122 adult patients who underwent their first allo-HSCT. The CT-based semi-automated measurement of subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), visceral-to-subcutaneous fat ratio (VSR), sarcopenia in terms of skeletal muscle index (SMI), and myosteatosis based on the skeletal muscle radiation attenuation (SM-RA) was performed. Cox regression analysis was used to assess the association of body composition parameters with OS.

RESULTS

In the univariate analysis, low SAT and myosteatosis were associated with lower OS (hazard ratio [HR] 2.02, 95% confidence interval [CI] 1.16-3.51, p = 0.01) and (HR 2.50, 95% CI 1.48-4.25, p =< 0.001), respectively. This association remained significant after adjusting for relevant covariates, with HR 2.32, 95% CI 1.23-4.38, p = 0.01 and HR 2.86, 95% CI 1.51-5.43, p =< 0.001, respectively. On the contrary, VAT, VSR, sarcopenia, and sarcopenic obesity were not statistically significant in OS. Severe post-transplant adverse events were more common in the low SAT group (odds ratio [OR] 3.12, 95% CI 1.32-7.40, p = 0.01) and OR 3.17, 95% CI 1.31-7.70, p =< 0.01 in the age- and sex-adjusted analysis.

CONCLUSION

Low SAT and myosteatosis may contribute to an increased risk of post-transplant mortality, while low SAT appears to increase the risk of severe post-transplant adverse events.

Association of low muscle mass with cognitive function and mortality in USA seniors: results from NHANES 1999-2002

BACKGROUND

Sarcopenia and cognitive impairment have been linked in prior research, and both are linked to an increased risk of mortality in the general population. Muscle mass is a key factor in the diagnosis of sarcopenia. The relationship between low muscle mass and cognitive function in the aged population, and their combined impact on the risk of death in older adults, is currently unknown. This study aimed to explore the correlation between low muscle mass and cognitive function in the older population, and the relationship between the two and mortality in older people.

METHODS

Data were from the National Health and Nutrition Examination Survey 1999-2002. A total of 2540 older adults aged 60 and older with body composition measures were included. Specifically, 17-21 years of follow-up were conducted on every participant. Low muscle mass was defined using the Foundation for the National Institute of Health and the Asian Working Group for Sarcopenia definitions: appendicular lean mass (ALM) (< 19.75 kg for males; <15.02 kg for females); or ALM divided by body mass index (BMI) (ALM: BMI, < 0.789 for males; <0.512 for females); or appendicular skeletal muscle mass index (ASMI) (< 7.0 kg/m2 for males; <5.4 kg/m2 for females). Cognitive functioning was assessed by the Digit Symbol Substitution Test (DSST). The follow-up period was calculated from the NHANES interview date to the date of death or censoring (December 31, 2019).

RESULTS

We identified 2540 subjects. The mean age was 70.43 years (43.3% male). Age-related declines in DSST scores were observed. People with low muscle mass showed lower DSST scores than people with normal muscle mass across all age groups, especially in the group with low muscle mass characterized by ALM: BMI (60-69 years: p < 0.001; 70-79 years: p < 0.001; 80 + years: p = 0.009). Low muscle mass was significantly associated with lower DSST scores after adjusting for covariates (ALM: 43.56 ± 18.36 vs. 47.56 ± 17.44, p < 0.001; ALM: BMI: 39.88 ± 17.51 vs. 47.70 ± 17.51, p < 0.001; ASMI: 41.07 ± 17.89 vs. 47.42 ± 17.55, p < 0.001). At a mean long-term follow-up of 157.8 months, those with low muscle mass were associated with higher all-cause mortality (ALM: OR 1.460, 95% CI 1.456-1.463; ALM: BMI: OR 1.452, 95% CI 1.448-1.457); ASMI: OR 3.075, 95% CI 3.063-3.088). In the ALM: BMI and ASMI-defined low muscle mass groups, participants with low muscle mass and lower DSST scores were more likely to incur all-cause mortality ( ALM: BMI: OR 0.972, 95% CI 0.972-0.972; ASMI: OR 0.957, 95% CI 0.956-0.957).

CONCLUSIONS

Low muscle mass and cognitive function impairment are significantly correlated in the older population. Additionally, low muscle mass and low DSST score, alone or in combination, could be risk factors for mortality in older adults.

Construction of an Exercise Intervention Program for Patients with Sarcopenic Obesity: A Delphi Method Study

Purpose

Construct an exercise intervention program for patients with sarcopenic obesity.

Material and Methods

Based on the COM-B theoretical model and evidence-based principles, the program was constructed using qualitative methods of literature analysis and Delphi method. The Delphi panel consisted of 15 experts from the fields of clinical medicine, rehabilitation medicine, medical technology, and nursing.

Results

Fifteen experts were consulted, and the consultation recovery rate was 100%; the authority coefficient of the 1st round was 0.83, with coefficients of variation ranging from 0.00 to 0.27, and importance scores ranging from (4.13±1.13) to (5±0); the authority coefficient of the 2nd round was 0.82, with coefficients of variation ranging from 0.00 to 0.20, and importance scores ranging from (4.53±0.64) to (5±0); Kendall's harmony coefficient was 0.102, 0.115, respectively, and the differences were statistically significant(P < 0.05). The constructed exercise intervention program for patients with sarcopenic obesity included 4 primary indicators, 12 secondary indicators, and 28 tertiary indicators.

Conclusion

The constructed exercise intervention program for patients with sarcopenic obesity is scientific, feasible and generalizable, and can provide useful reference for related personnel to develop exercise programs for patients with sarcopenic obesity.

Sarcopenic obesity in older adults: a clinical overview

Sarcopenic obesity is characterized by a concurrent decline in muscle mass and function, along with increased adipose tissue. Sarcopenic obesity is a growing concern in older adults owing to significant health consequences, including implications for mortality, comorbidities and risk of developing geriatric syndromes. A 2022 consensus statement established a new definition and diagnostic criteria for sarcopenic obesity. The pathophysiology of this condition involves a complex interplay between muscle, adipose tissue, hormonal changes, inflammation, oxidative stress and lifestyle factors, among others. Sarcopenic obesity is treated with a range of management approaches, such as lifestyle interventions, exercise, nutrition and medical therapies. Emerging therapies that were developed for treating other conditions may be relevant to sarcopenic obesity, including novel pharmacological agents and personalized approaches such as precision medicine. In this Review, we synthesize the current knowledge of the clinical importance of sarcopenic obesity, its assessment and diagnosis, along with current and emerging management strategies.

Prevalence of sarcopenic obesity in the older non-hospitalized population: a systematic review and meta-analysis

BACKGROUND

Sarcopenic obesity emerges as a risk factor for adverse clinical outcomes in non-hospitalized older adults, including physical disabilities, metabolic diseases, and even mortality. In this systematic review and meta-analysis, we investigated the overall SO prevalence in non-hospitalized adults aged ≥ 65 years and assessed the sociodemographic, clinicobiological, and lifestyle factors related to SO.

METHODS

We searched the PubMed, Embase, Cochrane Library, and Web of Science databases for studies reporting the prevalence of SO from database inception to October 2023. Two researchers independently screened the literature, evaluated the study quality, and extracted the data. Both fixed- and random-effects models were used in the meta-analysis to estimate the pooled SO prevalence and perform subgroup analyses. Publication and sensitivity bias analyses were performed to test the robustness of the associations.

RESULTS

Among 46 studies eligible for review and a total of 71,757 non-hospitalized older adults, the combined prevalence of SO was 14% (95% CI:11-17%, I2 = 99.5%, P < 0.01). Subgroup analysis according to lifestyle factors demonstrated that the SO prevalence was 17% (95% CI: 8-29%, I2 = 99.5%, P < 0.01) in older adults without exercise habits. Regarding clinicobiological factors, older adults with a history of falls (15% [95% CI: 10-22%, I2 = 82%, P < 0.01]), two or more chronic diseases (19% [95% CI: 10-29%, I2 = 97%, P < 0.01]), functional impairment (33% [95% CI: 29-37%, I2 = 0%, P = 0.95]), cognitive impairment (35% [95% CI: 9-65%, I2 = 83%, P = 0.02]), osteoporosis (20% [95% CI: 8-35%, I2 = 96%, P < 0.01]), high fasting glucose level (17% [95% CI: 1-49%, I2 = 98%, P < 0.01]), or the use of antipsychotics (13% [95% CI: 2-28%, I2 = 0%, P = 0.32]) exhibited a higher SO prevalence.

CONCLUSION

SO prevalence is high among non-hospitalized older adults, especially those with functional and cognitive impairments. Thus, SO is a potential problem for the aging population; implementation of planned interventions in the community is needed to reduce the prevalence and adverse outcomes of SO.

The relationship between sarcopenic obesity and changes in quadriceps muscle thickness and echo intensity in patients with stroke

BACKGROUND

Research findings on skeletal muscle degeneration in post-stroke sarcopenic obesity are limited. Thus, this study aimed to investigate the association between post-stroke sarcopenic obesity and quantitative and qualitative changes in skeletal muscles.

METHODS

This was a cross-sectional study conducted on patients with stroke admitted to the convalescent rehabilitation ward. For skeletal muscle assessment, an ultrasound system was used to measure quadriceps muscle thickness and echo intensity (QMT and QEI) on the paretic and non-paretic sides. Sarcopenic obesity was defined as the presence of both sarcopenia and obesity. Multiple regression analysis was performed to determine the relationships between sarcopenic obesity and QMT and QEI.

RESULTS

A total of 130 patients with stroke were included in this study (mean age: 69.4 ± 12.7 years). The prevalence of sarcopenic obesity was 23.1%. The multiple regression analysis showed that sarcopenic obesity was significantly negatively associated with QMT on both the paretic and non-paretic sides (paretic side: β =  -0.28, p < 0.001; non-paretic side: β =  -0.37, p < 0.001) and significantly positively associated with QEI (paretic side β = 0.21, p = 0.034; non-paretic side: β = 0.20, p = 0.029).

CONCLUSIONS

Post-stroke sarcopenic obesity was independently associated with quantitative and qualitative changes in skeletal muscles on both the paretic and non-paretic sides.

Associations Between Cognitive Function and Muscle Quality Among Community-Dwelling Older Adults: A Cross-Sectional Study

OBJECTIVE

To investigate whether muscle quality is related to cognitive function in older adults living in the community.

METHODS

The participants were 40 community-dwelling older adults without a diagnosis of dementia (mean age, 78.85 ± 6.40 years; 31 women). The dependent variable was the score on the mild cognitive impairment (MCI) index of the Japanese version of the Neurobehavioral Cognitive Status Examination Five (range: 0-6; higher scores indicate MCI or possible dementia).

RESULTS

Multiple regression with Bayesian statistics was performed for analysis of muscle quality, as indicated by echo intensity (EI), with skeletal muscle mass index, gait speed, physical activity level, age, and sex as covariates. EI was significantly associated with the MCI index (expected a posterior = 0.04 [95% Bayesian confidence interval: 0.01, 0.07], t = 2.47, β = 0.41, p = 0.019).

CONCLUSIONS

The results suggest that EI may be related to the cognitive function of older adults living in the community. Future studies should examine whether focusing on EI can help prevent cognitive decline among older adults..

Sarcopenic obesity is part of obesity paradox in dementia development: evidence from a population-based cohort study

BACKGROUND

Sarcopenic obesity, a clinical and functional condition characterized by the coexistence of obesity and sarcopenia, has not been investigated in relation to dementia risk and its onset.

METHODS

We included 208,867 participants from UK biobank, who aged 60 to 69 years at baseline. Dementia diagnoses were identified using hospital records and death register data. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazards models to evaluate the associations of obesity, sarcopenia, and sarcopenic obesity with dementia risk, stratified by sex. Stratified analyses were performed across dementia-related polygenic risk score (PRS). Restricted mean survival time models were established to estimate the difference and 95%CIs of dementia onset across different status. Additionally, linear regression models were employed to estimate associations of different status with brain imaging parameters. The mediation effects of chronic diseases were also examined.

RESULTS

Obese women with high PRS had a decreased risk (HR = 0.855 [0.761-0.961]), but obese men with low PRS had an increased risk (HR = 1.223 [1.045-1.431]). Additionally, sarcopenia was associated with elevated dementia risk (HRwomen = 1.323 [1.064-1.644]; HRmen = 2.144 [1.753-2.621]) in those with low PRS. Among those with high PRS, however, the association was only significant in early-life (HRwomen = 1.679 [1.355-2.081]; HRmen = 2.069 [1.656-2.585]). Of note, sarcopenic obesity was associated with higher dementia risk (HRwomen = 1.424 [1.227-1.653]; HRmen = 1.989 [1.702-2.323]), and results remained similar stratified by PRS. Considering dementia onset, obesity was associated with dementia by 1.114 years delayed in women, however, 0.170 years advanced in men. Sarcopenia (women: 0.080 years; men: 0.192 years) and sarcopenic obesity (women: 0.109 years; men: 0.511 years) respectively advanced dementia onset. Obesity, sarcopenia, and sarcopenic obesity were respectively related to alterations in different brain regions. Association between sarcopenic obesity and dementia was mediated by chronic diseases.

CONCLUSIONS

Sarcopenic obesity and sarcopenia were respectively associated with increased dementia risk and advanced dementia onset to vary degree. The role of obesity in dementia may differ by sex and genetic background.

Undernutrition in obese older adults by fat percentage

OBJECTIVE

The prevalence of obesity by fat percentage has seen a steady increase in older adults in recent years, secondary to increases in fat mass in body composition, even in healthy aging. Malnutrition is a common geriatric syndrome with serious clinical outcomes. Increases in fat mass and waist circumference with healthy aging should not prevent the risk of malnutrition from being masked. Malnutrition is often ignored in obese older people due to low BMI cut-off values in many screening tests. The present study seeks to raise awareness of the need to assess the frequency of undernutrition and related factors in obese older adults.

METHODS

The data of 2013 community-dwelling patients aged ≥ 60 years who applied to a university geriatrics outpatient clinic between April 2012 and November 2022 were analyzed retrospectively, of which 296 were found to be obese based on fat percentage and were included in the study. Demographic data and the presence of any geriatric syndromes were obtained retrospectively from the patient files, functional status was assessed using the KATZ Activities of Daily Living (ADL) Scale and the LAWTON-BRODY Instrumental Activities of Daily Living Scale (IADL); frailty was screened using FRAIL-scale; and the sample was assessed for malnutrition using the Mini Nutritional Assessment-Short Form (MNA-SF), with undernutrition defined as an MNA-SF score of [Formula: see text] The patients' fat percentage and weight were measured using a bioimpedance analyzer. Fatty obesity was defined using the Zoico methodology (fat percentage [Formula: see text] 27.3% for males, [Formula: see text] 40.7% for females)[Formula: see text] handgrip strength (HGS) was measured using a hand dynamometer, and probable sarcopenia was defined as low HGS based on regional cut-off values (35 kg for males, 20 kg for females).

RESULTS

The mean age of the 296 fatty obese older adults (102 males/194 females) was 74.4 + 6.5 years, and the median fat was 42.2% (27.4-59.5). Undernutrition was detected in 19.6% of the patients based on MNA-SF screening. A univariate analysis revealed age, sex, educational status, daily physical activity status, depression, difficulty in swallowing, chewing difficulty, probable sarcopenia, number of chronic diseases, and IADL to be associated with undernutrition, while a multivariate logistic regression analysis revealed depression [OR = 3.662, 95% CI (1.448-9.013), p = 0.005] and daily physical activity status [OR:0.601, 95% CI (0.417-0.867), p = 0.006] to be independently associated with malnutrition in obese older adults based on fat percentage.

CONCLUSION

 The present study clarifies the significance of undernutrition in obese older adults also in our country, and recommends undernutrition screening to be carried out, by fat percentage, on obese older adults, especially with depression and low daily physical activity.

Gender-specific moderating role of abdominal obesity in the relationship between handgrip strength and cognitive impairment

BACKGROUND & AIMS

Both low handgrip strength (HGS) and abdominal obesity (AO) are associated with cognitive impairment. However, it remains unclear whether low HGS and AO interact to affect cognition, and whether the synergistic effect varies by gender. This study aimed to examine whether the association between low HGS and incident cognitive impairment was moderated by AO among Chinese older men and women.

METHODS

We used the data of participants (≥60 years) from four waves (2011-2018) of the China Health and Retirement Longitudinal Study. We defined low HGS as the maximal HGS of <28 kg in men and <18 kg in women, and AO as waist circumference of ≥90 cm for men and ≥80 cm for women. Cognitive impairment was defined as a global cognitive score in the lowest 10th percentile. For each gender, we used subdistribution hazards model to estimate subdistribution hazard ratios (SHRs) for the association of low HGS and AO with incident cognitive impairment, treating mortality as the competing event and controlling for other covariates. Multiplicative interaction was assessed through a cross-product interaction term of low HGS and AO in the model. Additive interaction between low HGS and AO was evaluated by calculating the relative excess risk due to interaction (RERI) and attributable proportion due to interaction (AP).

RESULTS

We included 3704 participants (Mean age: 66.9 ± 5.81; 54.9% male). During the 7-year follow-up, 1133 events of interest occurred (731 cognitive impairments and 402 deaths). Incidence rates of cognitive impairment and mortality were 4.1 (95% CI: 3.8 to 4.4) and 2.2 (95% CI: 2.0 to 2.5) per 100 person-years. There were positive multiplicative (SHR for the product term = 1.974, 95% CI: 1.114 to 3.500) and additive interactions (RERI = 1.056, 95% CI: 0.027 to 2.086, AP = 0.454, 95% CI: 0.158 to 0.750) of low HGS and AO on the risk of cognitive impairment among older men. Male participants with both low HGS and AO showed an increased risk of cognitive impairment (SHR = 2.325, 95% CI: 1.498 to 3.609) compared with those without either. There was no evidence of interaction among older women (SHR for the product term = 1.151, 95% CI: 0.725 to 1.825; RERI = 0.044, 95% CI: -0.524 to 0.613; AP = 0.039, 95% CI: -0.458 to 0.536).

CONCLUSIONS

Low HGS and AO may interact to synergistically increase the risk of cognitive impairment among Chinese older men. Screening the highest-risk subpopulation, who may benefit most from neurocognitive prevention strategies, may maximize potential public health gains.

Clinical impacts of sarcopenic obesity on chronic obstructive pulmonary disease: a cross-sectional study

BACKGROUND

Sarcopenia and obesity are two abnormal body composition phenotypes, and sarcopenic obesity (SO) is characterized by both low skeletal muscle mass (sarcopenia) and high adiposity (obesity). SO negatively influences the clinical status of patients with chronic obstructive pulmonary disease (COPD). However, the studies exploring the prevalence and clinical effects of SO in COPD patients are limited. Our study aimed to elucidate the prevalence and impact of SO on COPD patients.

METHODS

In this cross-sectional study, the pulmonary function, St. George's Respiratory Questionnaire, exercise tolerance, body composition, and serum levels of resistin and TNF-α were assessed in 198 COPD patients. The clinical value of serum resistin and TNF-α for predicting SO in patients with COPD was evaluated.

RESULTS

In the 198 patients with COPD, the prevalence rates of sarcopenia, obesity, and SO in COPD patients were 27.27%, 29.8%, and 9.6%, respectively. Patients with SO experienced more severe symptoms of dyspnea and worse health related quality of life. The expression of resistin increased in patients with SO compared to other patients. The AUC value of serum resistin level for predicting SO was 0.870 (95% CI: 0.799-0.940). BMI (OR: 1.474, 95% CI: 1.124-1.934) and resistin (OR: 1.001, 95% CI: 1.000-1.002) levels were independent risk factors of SO in patients with COPD in Multivariate analysis.

CONCLUSION

The prevalence rates of SO in COPD patients was 9.6%. COPD accompanied by SO is significantly associated with worse pulmonary function and poor physical performance. Serum resistin may be a potential adjunct for predicting SO in COPD patients.

Spatiotemporal gait parameter fluctuations in older adults affected by mild cognitive impairment: comparisons among three cognitive dual-task tests

BACKGROUNDS

Gait disorder is associated with cognitive functional impairment, and this disturbance is more pronouncedly when performing additional cognitive tasks. Our study aimed to characterize gait disorders in mild cognitive impairment (MCI) under three dual tasks and determine the association between gait performance and cognitive function.

METHODS

A total of 260 participants were enrolled in this cross-sectional study and divided into MCI and cognitively normal control. Spatiotemporal and kinematic gait parameters (31 items) in single task and three dual tasks (serial 100-7, naming animals and words recall) were measured using a wearable sensor. Baseline characteristics of the two groups were balanced using propensity score matching. Important gait features were filtered using random forest method and LASSO regression and further described using logistic analysis.

RESULTS

After matching, 106 participants with MCI and 106 normal controls were recruited. Top 5 gait features in random forest and 4 ~ 6 important features in LASSO regression were selected. Robust variables associating with cognitive function were temporal gait parameters. Participants with MCI exhibited decreased swing time and terminal swing, increased mid stance and variability of stride length compared with normal control. Subjects walked slower when performing an extra dual cognitive task. In the three dual tasks, words recall test exhibited more pronounced impact on gait regularity, velocity, and dual task cost than the other two cognitive tests.

CONCLUSION

Gait assessment under dual task conditions, particularly in words recall test, using portable sensors could be useful as a complementary strategy for early detection of MCI.

Effects of non-pharmacological interventions on patients with sarcopenic obesity: A meta-analysis

OBJECTIVE

Systematic evaluation of the improvement effect of non-pharmacological intervention on patients with sarcopenic obesity.

METHODS

Wanfang, VIP, China National Knowledge Infrastructure (CNKI), SinoMed, Web of Science, Cochrane Library, PubMed, and Embase databases were searched systematically for randomized controlled trials (RCTS) and experimental studies of non-pharmacological interventions on patients with sarcopenic obesity. The retrieval period was from the establishment of the databases to October 31, 2022. Meta-analysis was conducted using RevMan 5.4.

RESULTS

A total of 18 studies involving 1,109 patients were included. Meta-analysis results showed that non-pharmacological interventions improved patients' body weight [mean difference, MD = -2.74, 95% CI (-4.79, -0.70), P = 0.009], body fat percentage [MD = -0.67, 95% CI (-0.96, -0.38), P<0.00001], grip strength [MD = 1.29, 95% CI (0.81, 1.77), P<0.00001], gait speed [MD = 0.05, 95% CI (0.03, 0.07), P<0.00001], and knee extension strength [MD = 2.56, 95% CI (1.30, 3.82), P<0.0001].

CONCLUSIONS

Non-pharmacological interventions can effectively improve the clinical symptoms and signs of patients with sarcopenic obesity. Dissemination of this information will be therapeutically useful.

TRIAL REGISTRATION

Registration. The PROSPERO No. is CRD42023403341.

Sarcopenic obesity using the ESPEN and EASO consensus statement criteria of 2022 - Results from the German KORA-Age study

OBJECTIVE

The recent consensus statement of ESPEN and EASO recommends reviewing existing datasets to assess the prevalence of sarcopenic obesity based on the new definition and diagnostic criteria. Therefore, this study aimed to determine the prevalence of sarcopenic obesity in a population-based study and to assess the association of this new definition with clinical traits.

METHODS

The KORA (Cooperative Health Research in the Region of Augsburg)-Age baseline examination (2008/2009) comprised 1079 participants aged 65 years and older from southern Germany. Sarcopenic obesity was defined in 998 participants (mean age 75.6 years, 498 women) with complete data according to the 2022 ESPEN and EASO algorithm, which includes reduced handgrip strength, reduced skeletal muscle mass per weight, and elevated fat mass. Body composition was measured using bioelectrical impedance analysis. Associations between sarcopenic obesity and physical activity, disability, multimorbidity, and polypharmacy were assessed using logistic regression analysis.

RESULTS

The overall prevalence of sarcopenic obesity was 4.5 % (5.0 % in men, 4.0 % in women). Sarcopenic obesity was associated with disability (2.87 [CI 1.84-4.48]), multimorbidity (≥ 2 comorbidities; 2.59 [CI 1.23-5.46]), polypharmacy (≥ 5 drugs; 1.96 [CI 1.05-3.63]), cognitive impairment (3.03 [CI 1.51-6.06]) and arthritis (2.66 [CI 1.39-5.07]) after adjusting for age, sex and marital status.

CONCLUSION

Sarcopenic obesity is prevalent in the older German population and is associated with several clinical traits. Future longitudinal studies are needed to further elucidate whether the observed associations could be causal.

Investigating the shared genetic architecture between schizophrenia and body mass index

Evidence for reciprocal comorbidity of schizophrenia (SCZ) and body mass index (BMI) has grown in recent years. However, little is known regarding the shared genetic architecture or causality underlying the phenotypic association between SCZ and BMI. Leveraging summary statistics from the hitherto largest genome-wide association study (GWAS) on each trait, we investigated the genetic overlap and causal associations of SCZ with BMI. Our study demonstrated a genetic correlation between SCZ and BMI, and the correlation was more evident in local genomic regions. The cross-trait meta-analysis identified 27 significant SNPs shared between SCZ and BMI, most of which had the same direction of influence on both diseases. Mendelian randomization analysis showed the causal association of SCZ with BMI, but not vice versa. Combining the gene expression information, we found that the genetic correlation between SCZ and BMI is enriched in six regions of brain, led by the brain frontal cortex. Additionally, 34 functional genes and 18 specific cell types were found to have an impact on both SCZ and BMI within these regions. Taken together, our comprehensive genome-wide cross-trait analysis suggests a shared genetic basis including pleiotropic loci, tissue enrichment, and shared function genes between SCZ and BMI. This work provides novel insights into the intrinsic genetic overlap of SCZ and BMI, and highlights new opportunities and avenues for future investigation.

A Higher Whole-Body Extracellular to Intracellular Water Ratio Is Associated with Increased Odds of Cognitive Impairment in Hemodialysis Patients

BACKGROUND

Cognitive impairment (CI) is highly prevalent in patients undergoing hemodialysis. Whether fluid overload with malnutrition as assessed by the ratio of extracellular water to intracellular water (ECW/ICW) is associated with CI in patients on maintenance hemodialysis (MHD) has yet to be studied.

OBJECTIVE

This study aimed to investigate the association between ECW/ICW and CI in patients with MHD.

METHODS

We conducted a multicenter, cross-sectional study that enrolled 3,025 adult patients with MHD. Cognitive function was assessed through the Mini-Mental State Examination. The ECW/ICW was derived from a portable body composition monitor and analyzed by quartiles.

RESULTS

23.04% of participants had CI in our study. The prevalence of CI tended to increase as the quartiles of the ECW/ICW ratio increased. Unadjusted analysis showed that participants in quartile 4 were 3.02 times more likely to have a CI compared to those in quartile 1. After adjusting for age, sex, education, smoking status, body mass index, dialysis vintage, history of hypertension, and history of stroke, the adjusted OR (95% CI) for the highest quartile of ECW/ICW ratio was 1.36 (1.01, 1.83) for CI compared with the lowest quartile. Interestingly, the association between ECW/ICW ratio and CI persisted across all subgroups stratified by age, gender, history of diabetes, and stroke. (p for interaction > 0.05 for all).

CONCLUSION

An increased ECW/ICW ratio is associated with higher odds of cognitive impairment in patients undergoing hemodialysis.

Waist-to-calf circumstance ratio and cognitive function among Chinese older adults: Mediating roles of physical performance and social activity

Background

In light of the potentially detrimental effects of central fat and decreased muscle mass on cognitive function, it would be beneficial to learn more about the mediating mechanisms underpinning the association between the two. The purpose of this study is to determine the association between waist-to-calf circumstance ratio (WCR) and cognitive function, as well as to investigate whether physical performance and social activity mediate the relationship between WCR and cognitive function among older Chinese adults.

Methods

An analysis of 9,652 older Chinese adults was conducted during the 2018 wave of the Chinese Longitudinal Health Longevity Survey (CLHLS). The Mini-Mental State Examination (MMSE) and a self-reported scale were used to measure cognitive function, physical performance, and social activity, respectively. Multiple linear regression and mediation analyses were conducted.

Results

The findings suggest that a high WCR had a significant negative association with cognitive function (B = -0.535, 95% CI: -0.754, -0.317). Mediation analysis revealed that a high WCR influenced old adults' cognitive function in three ways: first, through the partial mediating effect of physical performance (B = -0.270; 95% CI: -0.340, -0.203); second, through the partial mediating effect of social activity (B = -0.035; 95% CI: -0.055, -0.017); and third, through the serial mediating effects of physical performance and social activity (B = -0.021, 95% CI: -0.029, -0.015).

Conclusion

The study results suggest the adverse impact of a high WCR on older adults' cognitive function, and the possible mechanisms of physical performance and social activity by which the association takes place. Multidimensional health and social interventions aimed at improving physical, social, and cognitive functioning among older adults with sarcopenic obesity are recommended.

The Prevalence and Agreement of Sarcopenic Obesity Using Different Definitions and Its Association with Mild Cognitive Impairment

BACKGROUND

The consistent definition of sarcopenic obesity (SO) is limited, its association with mild cognitive impairment (MCI) has not been clarified.

OBJECTIVE

This study aimed to evaluate the prevalence and agreement of SO using different definitions and the association between SO and MCI.

METHODS

SO was diagnosed by the co-existence of sarcopenia defined by the Asia Working Group for Sarcopenia (AWGS) and obesity by body mass index (BMI), visceral fat area (VFA), waist circumference (WC), or body fat percentage (BF%). Cohen's kappa was used to assess the agreement between the different definitions. The association between SO and MCI was assessed using multivariable logistic regression.

RESULTS

Among 2,451 participants, the prevalence of SO ranged from 1.7% to 8.0% under different definitions. SO defined by AWGS and BMI (AWGS+BMI) showed fair agreements with the other three criteria (κ ranged from 0.334 to 0.359). The other criteria showed good agreements with each other. The κ statistics were 0.882 for AWGS+VFA and AWGS+BF%, 0.852 for AWGS+VFA and AWGS+WC, and 0.804 for AWGS+BF% and AWGS+WC, respectively. When using different diagnoses of SO, compared with the health group, the adjusted ORs of MCI for SO were 1.96 (95% CI: 1.29-2.99, SO: AWGS+WC), 1.75 (95% CI: 1.14-2.68, SO: AWGS+VFA), 1.94 (95% CI: 1.29-2.93, SO: AWGS+BF%), and 1.45 (95% CI: 0.67-3.12, SO: AWGS+BMI), respectively.

CONCLUSION

Using different obesity indicators combined with AWGS to diagnose SO, BMI had lower prevalence and agreement compared with other three indicators. SO was associated with MCI under different methods (WC, VFA, or BF%).

Recent Updates on Associations among Various Obesity Metrics and Cognitive Impairment: from Body Mass Index to Sarcopenic Obesity

Obesity and obesity-associated morbidity continues to be a major public health issue worldwide. Dementia is also a major health concern in aging societies and its prevalence has increased rapidly. Many epidemiologic studies have shown an association between obesity and cognitive impairment, but this relationship is not as well established as other comorbidities. Conflicting results related to the age and sex of participants, and the methodology used to define obesity and dementia may account for the uncertainty in whether obesity is a modifiable risk factor for dementia. More recently, sarcopenia and sarcopenic obesity have been reported to be associated with cognitive impairment. In addition, new mediators such as the muscle-myokine-brain axis and gut-microbiota-brain axis have been suggested and are attracting interest. In this review, we summarize recent evidence on the link between obesity and cognitive impairment, especially dementia. In particular, we focus on various metrics of obesity, from body mass index to sarcopenia and sarcopenic obesity.

Associations of body mass index and sarcopenia with screen-detected mild cognitive impairment in older adults in Colombia

Background and objective

More research is required to understand associations of body mass index (BMI) and sarcopenia with cognition, especially in Latin America. The objective of this study was to investigate associations of BMI and sarcopenia with mild cognitive impairment in Colombia.

Design, setting, and participants

Data were from the National Survey of Health, Wellbeing and Aging in Colombia (SABE Colombia, in Spanish). Community-dwelling adults aged 60 years or older were invited to participate.

Methods

Trained interviewers administered a shorter version of the mini-mental state examination and mild cognitive impairment was defined as a score of 12 or less out of 19. Body mass index was defined using standard cut-offs. Sarcopenia was defined as low grip strength or slow chair stands. Logistic regression models were adjusted for age, sex, height, education, income, civil status, smoking, and alcohol drinking.

Results

The prevalence of mild cognitive impairment was 20% in 23,694 participants in SABE Colombia and 17% in 5,760 participants in the sub-sample in which sarcopenia was assessed. Overweight and obesity were associated with decreased risk of mild cognitive impairment and sarcopenia was associated with increased risk. Sarcopenia was a risk factor for mild cognitive impairment in those with normal BMI (adjusted model included 4,911 men and women). Compared with those with normal BMI and without sarcopenia, the odds ratio for mild cognitive impairment was 1.84 in those with normal BMI and sarcopenia (95% confidence interval: 1.25, 2.71). Sarcopenia was also a risk factor in those with obesity but did not present a greater risk than sarcopenia alone. Compared with those with normal BMI and without sarcopenia, the odds ratio was 1.62 in those with obesity and sarcopenia (95% confidence interval: 1.07, 2.48). Sarcopenia was not a risk factor for mild cognitive impairment in those with overweight. Similar results were observed when reference values from Colombia were used to set cut-offs for grip strength. Similar results were also observed in cross-validation models, which suggests the results are robust.

Conclusion

This is the first study of the combined associations of sarcopenia and obesity with cognition in Colombia. The results suggest that sarcopenia is the major predictor of screen-detected mild cognitive impairment in older adults, not overweight or obesity.

Demand Coupling Drives Neurodegeneration: A Model of Age-Related Cognitive Decline and Dementia

The societal burden of Alzheimer's Disease (AD) and other major forms of dementia continues to grow, and multiple pharmacological agents directed towards modifying the pathological "hallmarks" of AD have yielded disappointing results. Though efforts continue towards broadening and deepening our knowledge and understanding of the mechanistic and neuropathological underpinnings of AD, our previous failures motivate a re-examination of how we conceptualize AD pathology and progression. In addition to not yielding effective treatments, the phenotypically heterogeneous biological processes that have been the primary area of focus to date have not been adequately shown to be necessary or sufficient to explain the risk and progression of AD. On the other hand, a growing body of evidence indicates that lifestyle and environment represent the ultimate level of causation for AD and age-related cognitive decline. Specifically, the decline in cognitive demands over the lifespan plays a central role in driving the structural and functional deteriorations of the brain. In the absence of adequate cognitive stimulus, physiological demand-function coupling leads to downregulation of growth, repair, and homeostatic processes, resulting in deteriorating brain tissue health, function, and capacity. In this setting, the heterogeneity of associated neuropathological tissue hallmarks then occurs as a consequence of an individual's genetic and environmental background and are best considered downstream markers of the disease process rather than specific targets for direct intervention. In this manuscript we outline the evidence for a demand-driven model of age-related cognitive decline and dementia and why it mandates a holistic approach to dementia treatment and prevention that incorporates the primary upstream role of cognitive demand.