Weakness Thresholds Are Differentially Linked to Cognitive Function by Obesity Status in Older Americans

Area of Science:

• Gerontology
• Neurology
• Public Health

Background:

• Muscle weakness is a significant concern in aging populations.
• Operationalizing weakness using different thresholds can influence its association with cognitive health.
• Obesity status is a critical factor to consider when examining weakness and cognitive impairment.

Purpose of the Study:

• To investigate the association between different weakness thresholds and future cognitive impairment in older adults.
• To analyze these associations based on obesity status.
• To determine if absolute, body mass normalized, or BMI normalized weakness thresholds provide different insights.

Main Methods:

• Secondary data analysis of the Health and Retirement Study (2006-2018).
• Handgrip strength (HGS) measured using a dynamometer; weakness defined by sex-specific thresholds (absolute, body mass normalized, BMI normalized).
• Cognitive function assessed using the modified Telephone Interview of Cognitive Status; cognitive impairment defined as a score ≤10. Obesity defined as BMI ≥30 kg/m².

Main Results:

• Older adults without obesity below the absolute weakness threshold had 1.54 times greater odds of cognitive impairment.
• Individuals with obesity showed increased odds of cognitive impairment across all weakness thresholds (absolute: 1.89, body mass normalized: 2.17, BMI normalized: 1.75).
• Those below all weakness thresholds had higher impairment odds: 1.32 for non-obese and 2.76 for obese individuals.

Conclusions:

• The definition of weakness, particularly the thresholds used, significantly affects its relationship with cognitive impairment in older adults.
• Obesity status further modifies the association between weakness and cognitive decline.
• Healthcare providers should consider both body size and specific weakness metrics when assessing cognitive risk in older populations.