Handgrip Linked to Cognition In Mood Disorders, Schizophrenia

Handgrip strength may provide a useful indicator of cognitive impairment in people with schizophrenia, major depression, and bipolar disorder, according to separate reports by the same research team in JAMA Psychiatry and Schizophrenia Bulletin.

Joseph Firth, Ph.D., of the University of Western Sydney and colleagues found consistently positive relationships between higher grip strength and better cognition in the general population, in patients with schizophrenia, and in those with mood disorders.

They analyzed data from the UK Biobank—a nationwide, health-oriented, cohort study conducted across the United Kingdom. In the Schizophrenia Bulletin report, baseline data from the Biobank collected between 2007 and 2010 were analyzed, including 475,397 individuals from the general population and 1,162 individuals with schizophrenia.

As part of the UK Biobank study, patients had maximal handgrip strength assessed. Handgrip from both left and right hands was measured while participants were seated in an upright position. A single trial was conducted for each hand.

Cognitive functioning was assessed using a 15-minute computerized battery, which was developed specifically for the UK Biobank study. The battery consisted of five individual tasks, quantifying performance in five separate cognitive domains as follows:

• Reaction time: mean response time in milliseconds to a prespecified visual stimuli.

• Reasoning: number of verbal and numerical logic problems solved in two minutes.

• Numeric memory: maximum length of a string of digits correctly recalled.

• Visuospatial memory: number of attempts required to correctly match six pairs of symbol cards following a brief visual presentation.

• Prospective memory: assessment measuring if participants succeed or fail to act on an earlier instruction after a delay period.

Firth and colleagues then analyzed the relationship between grip strength and the five cognitive domains, controlling for age, gender, body weight, education, and geographical region.

In the general population, higher grip strength was positively associated with reasoning, number memory, and prospective memory. Among patients with schizophrenia, grip strength was positively associated with visual memory and reaction time, while prospective memory approached statistical significance. (Results for tests reflecting other cognitive domains also found the same association but fell short of statistical significance because of the small sample size completing the tests, according to Firth and colleagues.)

“Impairments in both working memory and processing speed are pervasive among people with schizophrenia, and these domains are among the most important neurocognitive predictors of real-world social and occupational functioning in this population,” Firth and colleagues wrote.

William Carpenter, M.D., editor of Schizophrenia Bulletin, told Psychiatric News that the findings relating handgrip strength to cognitive impairment could prove extremely important if borne out in replication studies. “This seems especially likely since the same findings were shown by the same research group with regard to mood disorders,” he said.

“Motor pathology is important in a number of mental illnesses but is often subtly expressed,” he said. “Movement and motor disorders in schizophrenia received much attention in the 19th century and first half of the 20th century, but they have received little attention in contemporary research or clinical practice outside of adverse motor effects of medications. Motor pathology has been completely ignored in drug discovery for schizophrenia.”

Carpenter said that experts in catatonia believe many schizophrenia patients have subtle, treatable catatonia-like features that are frequently missed in routine clinical care. “Altered motor mechanism may play a role in social dysfunction—such as impaired gesturing or deviations in eye contact when communicating with someone,” he said.

He added that it is possible that the brain systems governing motor movements may also determine thought disorder, reality distortion, and negative symptoms. “If that were found to be true, it would open up an entirely new avenue for drug discovery,” Carpenter said.

In the JAMA Psychiatry report, Firth and colleagues reported analysis of 110,067 people who had their handgrip strength evaluated as part of the UK Biobank study, including 85,893 participants with no indication of any mood disorders, 22,699 with recurrent major depression, and 1,475 with bipolar disorder (type I or type II).

In participants with major depression and no indication of any mood disorders, greater handgrip strength was a significant predictor of better cognitive performance in all five domains: visual memory, reaction time, reasoning, number memory, and prospective memory. In people with bipolar disorder, greater handgrip strength was significantly associated with visual memory, reaction time, reasoning, and prospective memory. 

“To our knowledge, this study is the first to identify handgrip strength as a marker of cognitive function in mood disorders,” Firth and colleagues wrote. “However, the cross-sectional design of this investigation means that further longitudinal and mechanistic research must be conducted to determine the causative nature of the association between handgrip strength and cognition in psychiatric populations.”

Noting that strength training exercises have been shown to improve cognitive functioning in aging populations, the authors suggested that improving muscular fitness may be a “therapeutic target” for individuals with mood disorders. 

“Future research should investigate causality, assess the functional implications of handgrip strength in psychiatric populations, and examine how interventions to improve muscular fitness affect neurocognitive status and socio-occupational functioning,” they concluded. ■