Get a Grip: Strength and Cognition in Schizophrenia

Handgrip is a simple proxy for muscular strength and a clinically useful measure of muscular function.

Weaker handgrip strength is associated with poorer quality of life [1], increased mortality [2], and poorer cognition in aging populations[3].

No previous studies have investigated the association between handgrip strength and cognition in patients with schizophrenia.

Firth and colleagues[4] used population-scale data to investigate the relationship between maximal handgrip strength and cognition (across 5 domains) in people with and without schizophrenia.

Design
• The authors performed a cross-sectional analysis of data collected from 2007 to 2010 from the baseline assessment for the United Kingdom Biobank.
• Patients with neurological conditions associated with impaired cognition were excluded
• The United Kingdom Biobank is integrated with hospital records, allowing authors to stratify participants based on the presence or absence of an ICD-10 diagnosis of non-affective psychosis (F20-29)

Methods
• Handgrip strength was performed using a hand dynamometer, with a single trial for each hand
• The maximal score for the (self-reported) dominant hand was used in all analyses
• Cognition was assessed using a 15-minute computerized batter
• Each cognitive domain was analyzed using (generalized) linear mixed models, controlling for age, sex, weight, education, and geography, and testing center

Findings
• 476,559 participants had measurements of handgrip strength and at least one cognitive domain
• 1162 participants with schizophrenia were included in the cohort
• Mean age was 54 for schizophrenia and 57 for controls.  54% of patients and 45% of controls were male
• >95% of subjects completed the visual memory and reaction time tasks; <than 40% of subjects completed the other cognitive tasks

Key points
• In the general population sample, higher handgrip strength was significantly and positively associated with better performance on visual memory, reaction time, reasoning, number memory, and prospective memory tasks
• In patients with schizophrenia, higher handgrip strength was a significant positive predictor of better visual memory and reaction time, and predicted prospective memory at the trend level
• The magnitude of these associations was similar in patients with schizophrenia and in the general population
• The pattern of findings was unchanged when considering only subjects age 55 or younger, and also
after controlling for waist circumference and past history of cardiovascular disease

Discussion
• The authors concluded that theirs is the first study of handgrip strength and cognition in patients with schizophrenia, and the largest general population sample of this association to date, particular in middle-aged adults.
• A limitation of the study is that fewer participants in the schizophrenia sample completed all of the cognitive tasks, which may have impacted on statistical power

Take Home Points
• Handgrip strength is correlated with cognition in the general population and in schizophrenia
• Further research is needed regarding the direction and mechanism(s) of these associations, towards novel approaches for the assessment (and even potentially the treatment of) cognitive impairment in patients with schizophrenia

Dr. Miller is Associate Professor in the Department of Psychiatry and Health Behavior at Augusta University in Augusta, GA, and Schizophrenia Section Editor for Psychiatric Times. He reports no conflicts of interest concerning the subject matter of this slide show.