Gripping Theory Offers Clue to Predicting Cognitive Decline

Batya Swift Yasgur, MA, LSW

June 08, 2020

Low or asymmetrical handgrip strength may be an indicator of cognitive decline in seniors, new research suggests.

Investigators analyzed handgrip strength in over 17,000 adults aged 50 years and older and found that those with both asymmetry and weakness had a twofold increase risk of accelerated cognitive decline.

In particular, those with the greatest odds for lower cognitive functioning had considerably more strength in their nondominant than their dominant hand.

"Having weakness, as measured by maximal handgrip strength, and/or wide strength differences between hands, could be a clue for low cognitive functioning," lead author Ryan McGrath, PhD, assistant professor in the Department of Health, Nutrition, and Exercise Sciences, North Dakota State University, told Medscape Medical News.

"If a person has weakness and/or handgrip strength asymmetry, a more comprehensive cognitive evaluation may want to be considered — or even evaluations of other age-related health conditions such as frailty," McGrath said.

The study was published online May 30 in the Journal of the American Geriatric Society.

Indicator of Neural System Deficits

"There is an accumulating amount of evidence that physical measures, such as handgrip strength, are associated with cognitive impairment," McGrath said.

Previous studies focusing on cognition indicate that imbalances in muscle strength "could be linked to the neural system deficits that drive low cognitive functioning."

The researchers therefore "wanted to enhance handgrip strength protocols by also evaluating handgrip strength asymmetry because we are usually only interested in maximal handgrip strength," said McGrath.

To investigate, the researchers analyzed a sample of 17,163 individuals (median age, 65 years [SD, 10.1 years]; 42.2% male; 68.1% non-Hispanic white; 17.7% non-Hispanic black), drawn from the 2006 to 2016 waves of the Health and Retirement Study, a longitudinal study that monitors a variety of factors in aging Americans.

Most participants rated their health as "very good" or "good" (31.2% and 31.8%, respectively).

The researchers assessed cognitive function at each wave of the study using the Telephone Interview for Cognitive Status with "lower" status defined as ≤ 11 for participants ages 50‐64 years and ≤ 10 for those aged ≥ 65 years.

Handgrip strength of both dominant and nondominant hands was measured using a handgrip dynamometer, with "weakness" defined as handgrip strength < 26 kg in men or < 16 kg in women.

Participants with handgrip strength > 10% stronger on either hand were considered as having "any [handgrip strength] asymmetry," and participants with handgrip strength > 10% stronger on their dominant or nondominant hand were considered as having "dominant" or "nondominant" handgrip strength asymmetry, respectively.

Quick, Feasible Screen

Of the 17,163 study participants, 48% had symmetric handgrip strength, 43% had dominant handgrip strength asymmetry, and 9% had nondominant handgrip strength asymmetry.

Compared with participants with symmetric handgrip strength and no weakness, those with any handgrip strength asymmetry alone had 15% greater odds for lower cognitive functioning, participants with weakness alone had 64% greater odds for lower cognitive functioning, and those with both handgrip strength asymmetry and weakness had 95% greater odds for lower cognitive functioning.

The odds of lower cognitive function were even greater when examining hand dominance specifically. Those with dominant handgrip strength symmetry alone, nondominant handgrip strength asymmetry alone, weakness alone, dominant handgrip strength asymmetry and weakness, and nondominant handgrip strength asymmetry and weakness had 12%, 27%, 64%, 89%, and 110% greater odds for lower cognitive functioning, respectively.

"The associations for low cognitive function [and handgrip asymmetry] were exacerbated when those with handgrip strength asymmetry also had weakness," said McGrath.

"We recommend that measures of handgrip strength asymmetry be used alongside assessment of weakness to improve the prognostic value of handgrip dynamometers," he added.

He noted that the "feasibility for completing handgrip strength measurements are high [and] opportunities for measuring handgrip strength at home are emerging."

Simple Tool

Commenting on the study for Medscape Medical News, Keith Fargo, PhD, director of scientific engagement for the Alzheimer's Association, said the finding is "intriguing" but added that it "needs to be replicated in larger and more diverse study groups."

Fargo, who was not involved with the study, said that it is "important to note that handgrip strength is not a tool used to assess current or future cognitive function, and that this topic may be worth further investigation, since it is relatively simple to administer and measure."

For example, "it could be a simple screening tool that could indicate the need for a more comprehensive cognitive evaluation [but] we simply don't know at this point," Fargo stated.

McGrath noted that some healthcare providers use measures of handgrip strength to primarily assess muscle function, "but overall the use of handgrip strength in routine geriatric health assessments is generally absent."

He encourages healthcare providers "to use measure of handgrip strength, given the robust health information it provides and procedural ease."

However, he cautioned, handgrip strength "methodologies are continually evolving and the associations of handgrip strength with clinically relevant outcomes are wide-ranging, thus healthcare providers should understand how to administer handgrip strength protocols and what handgrip strength is assessing."

No source of study funding was reported. The authors and Fargo report no relevant financial relationships.

J Am Geriatr Soc. Published online May 30, 2020. Abstract

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