Association Between Sarcopenia and Cognitive Impairment in Community-Dwelling Population

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Association Between Sarcopenia and Cognitive Impairment in Community-Dwelling Population

Introduction

Cognitive impairment, a neurodegenerative condition, encompasses a spectrum from mild cognitive decline to dementia. It represents a significant public health concern, particularly among aging populations, due to its impact on independence and quality of life. Sarcopenia, another age-related condition, is characterized by progressive loss of skeletal muscle mass, strength, and physical performance. While traditionally viewed as a musculoskeletal disorder, emerging evidence suggests shared pathophysiological pathways between sarcopenia and cognitive impairment. Both conditions may involve oxidative stress, chronic inflammation, mitochondrial dysfunction, and hormonal dysregulation. These overlapping mechanisms have spurred interest in exploring potential associations between sarcopenia and cognitive decline. However, prior studies have yielded inconsistent results, with some reporting significant links and others finding no association. This study investigates the relationship between sarcopenia and cognitive impairment in a community-based elderly population in China.

Methods

Study Design and Participants

A cross-sectional health survey was conducted from November 2016 to February 2017 in the Ximen community of Ningbo, China. Participants aged ≥65 years who were functionally independent in daily activities were included. Exclusion criteria encompassed severe systemic conditions such as advanced cardiac, cerebrovascular, pulmonary, or neurological diseases, as well as cancer diagnoses. From an initial pool of 1,047 individuals, 124 were excluded due to incomplete data on physical or cognitive assessments, resulting in a final sample of 923 participants. Ethical approval was obtained from the institutional review board of HwaMei Hospital, and written informed consent was secured from all participants.

Diagnostic Criteria

Sarcopenia was diagnosed using criteria from the Asian Working Group for Sarcopenia (AWGS). Three components were assessed:

  1. Low muscle mass: Skeletal muscle mass index (SMI) <7.0 kg/m² for men and <5.7 kg/m² for women, measured via bioelectrical impedance analysis.
  2. Low muscle strength: Handgrip strength <26 kg (men) or <18 kg (women).
  3. Low physical performance: Gait speed <0.8 m/s on a 4-meter walk test.

Cognitive function was evaluated using the Mini-Mental State Examination (MMSE), with impairment defined as:

  • MMSE <20 for illiterate individuals
  • MMSE <22 for those with 1–6 years of education
  • MMSE 6 years of education

Data Collection and Analysis

Demographic characteristics (age, gender, education level), lifestyle factors (smoking, alcohol use), anthropometric measurements (BMI, body fat rate), and comorbidities (hypertension, diabetes, dyslipidemia) were recorded. Statistical analyses included univariate logistic regression and propensity score matching to control for confounding variables such as age, BMI, and comorbidities. Analyses were performed using Stata 13, with statistical significance set at P<0.05.

Results

Participant Characteristics

The cohort comprised 923 individuals (mean age: 72.5±5.3 years), with 100 (10.8%) classified as having cognitive impairment. Key differences between cognitively impaired and normal groups included:

  • Age: 74.6±5.5 vs. 72.1±5.1 years (P<0.001)
  • Education: Higher proportion of illiteracy in the cognitive impairment group (24% vs. 15%, P=0.009)
  • Physical performance:
    • Handgrip strength: 23.3±8.3 kg vs. 25.2±8.4 kg (P<0.001)
    • Gait speed: 1.07±0.28 m/s vs. 1.19±0.24 m/s (P<0.001)

Association Between Sarcopenia and Cognitive Impairment

Unadjusted Analysis:
Sarcopenia components showed varying associations:

  • Low physical performance: OR=2.69 (95% CI:1.42–5.08, P=0.002)
  • Sarcopenia (composite diagnosis): OR=2.04 (95% CI:1.16–3.57, P=0.013)
    Other components like low muscle mass (OR=1.43, P=0.120) and low handgrip strength (OR=1.54, P=0.052) did not reach significance.

Adjusted Analysis (Propensity Score Matching):
After controlling for age, BMI, comorbidities, and lifestyle factors, none of the sarcopenia components retained statistical significance:

  • Low physical performance: OR=1.65 (95% CI:0.68–4.00, P=0.271)
  • Sarcopenia: OR=2.22 (95% CI:0.94–5.21, P=0.067)

Subgroup Comparisons

Propensity score-matched analysis (1:1 ratio, N=200) confirmed the absence of significant associations. For instance, sarcopenia prevalence did not differ meaningfully between cognitive impairment and normal groups after adjustment (15.0% vs. 10.0%, P=0.271).

Discussion

Key Findings

This study found no independent association between sarcopenia and cognitive impairment after adjusting for confounders. While initial unadjusted models suggested links between low physical performance or sarcopenia with cognitive decline, these associations were attenuated upon rigorous statistical control. Notably, age and education level emerged as stronger predictors of cognitive status than sarcopenia components.

Contextualizing the Results

The null findings align with a French cohort study of elderly women that found no association between sarcopenia and dementia risk. However, they contrast with Korean research linking slow gait speed (a sarcopenia marker) to cognitive impairment. These discrepancies may stem from:

  1. Population differences: Variations in diagnostic criteria, age ranges, or comorbidities across studies.
  2. Assessment tools: Use of MMSE versus other cognitive tests (e.g., Montreal Cognitive Assessment).
  3. Confounding factors: Inadequate control for variables like vascular risk factors in prior studies.

Mechanistic Considerations

Shared biological pathways between sarcopenia and cognitive decline—such as inflammation, insulin resistance, and hormonal changes—suggest plausible interactions. However, this study implies these mechanisms may not manifest as direct clinical associations in community-dwelling elders without severe comorbidities.

Limitations

  1. Cross-sectional design: Precludes causal inference.
  2. Cognitive assessment: MMSE may lack sensitivity for early-stage impairment compared to detailed neuropsychological batteries.
  3. Geographic specificity: Results may not generalize to institutionalized or younger populations.
  4. Diagnostic thresholds: AWGS criteria for sarcopenia might not capture subtle muscle-cognition relationships.

Clinical Implications

The findings suggest that sarcopenia screening alone may not identify individuals at risk for cognitive impairment. Comprehensive geriatric assessments should prioritize age, education, and vascular health factors. However, physical performance measures like gait speed could still serve as practical indicators for further cognitive evaluation in resource-limited settings.

Conclusions

In this large community-based sample of Chinese older adults, sarcopenia was not independently associated with cognitive impairment after accounting for confounding variables. While initial associations were observed with physical performance measures, these did not persist in adjusted models. Future research should employ longitudinal designs to clarify temporal relationships and explore whether specific sarcopenia subtypes (e.g., severe muscle loss with inflammation) show stronger links to neurodegeneration.

doi.org/10.1097/CM9.0000000000001310

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