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

Weakness can be operationalized with several thresholds, which in turn, could impact associations with cognitive impairment when considering obesity status.

We examined the associations of absolute, normalized, and collective weakness thresholds on future cognitive impairment by obesity status in older adults.

We performed a secondary data analysis on the 2006-2018 waves of the Health and Retirement Study. A spring-type dynamometer collected handgrip strength (HGS). Males were categorized weak if their HGS was <35.5-kg (absolute), <0.45-kg/kg (body mass normalized), or <1.05-kg/kg/m² (body mass index (BMI) normalized), while females were defined as weak if their HGS was <20.0-kg, <0.337-kg/kg, or <0.79-kg/kg/m². The modified Telephone Interview of Cognitive Status examined cognitive function. Persons scoring ≤10 had a cognitive impairment. Obesity was categorized as BMI ≥30 kg/m².

We included 7,532 and 3,584 persons aged ≥65-years living without and with obesity, respectively. Those without obesity but beneath the absolute weakness threshold had 1.54 (95% confidence interval (CI): 1.24-1.91) greater odds for future cognitive impairment. Persons with obesity and beneath each threshold also had greater odds for future cognitive impairment: 1.89 (95% CI: 1.28-2.78) for absolute, 2.17 (95% CI: 1.02-4.62) for body mass normalized, and 1.75 (95% CI: 1.10-2.80) for BMI normalized. Older Americans without obesity but underneath all the weakness thresholds had 1.32 (95% CI: 1.00-1.74) greater odds for impairment in cognitive function, while persons with obesity had 2.76 (95% CI: 1.29-5.93) greater odds.

There should be consideration for how body size and different weakness thresholds may influence future cognitive outcomes.