Can handgrip strength provide an indication of cognitive functioning in people with major depression or bipolar disorder and healthy controls?
In this cross-sectional analysis of a population-scale data set of 110 067 individuals, handgrip strength was significantly associated with all 5 domains of cognition in people with major depression and in healthy controls, independently of confounding factors. Similar associations, but to a lesser extent, were observed in those with bipolar disorder.
Handgrip strength is associated with overall cognition in individuals with and without major depression; muscular function may provide a proxy for assessing neurocognitive impairment and present a novel interventional outcome for targeting cognitive improvement.
Objective physical fitness measures, such as handgrip strength, are associated with physical, mental, and cognitive outcomes in the general population. Although people with mental illness experience reduced physical fitness and cognitive impairment, the association between muscular strength and cognition has not been examined to date.
To determine associations between maximal handgrip strength and cognitive performance in people with major depression or bipolar disorder and in healthy controls.
Design, Setting, and Participants
In a multicenter, population-based study conducted between February 13, 2005, and October 1, 2010, in the United Kingdom, cross-sectional analysis was conducted of baseline data from 110 067 participants in the UK Biobank. Data analysis was performed between August 3 and August 18, 2017. Invitations were mailed to approximately 9.2 million UK homes, recruiting 502 664 adults, all aged 37 to 73 years. Clinically validated measures were used to identify individuals with major recurrent depression (moderate or severe) or bipolar disorder (type I or type II) and healthy controls (those with no indication of present or previous mood disorders).
Main Outcomes and Measures
Handgrip dynamometry was used to measure muscular function. Cognitive functioning was assessed using computerized tasks of reaction time, visual memory, number memory, reasoning, and prospective memory. Generalized linear mixed models assessed the association between handgrip strength and cognitive performance, controlling for age, educational level, sex, body weight, and geographic region.
Of the 110 067 participants, analyses included 22 699 individuals with major depression (mean [95% range] age, 55.5 [41-68] years; 7936 [35.0%] men), 1475 with bipolar disorder (age, 54.4 [41-68] years; 748 [50.7%] men), and 85 893 healthy controls (age, 53.7 [41-69] years; 43 000 [50.0%] men). In those with major depression, significant positive associations (P < .001) between maximal handgrip strength and improved performance on all 5 cognitive tasks were found, including visual memory (coefficient, −0.146; SE, 0.014), reaction time (coefficient, −0.036; SE, 0.002), reasoning (coefficient, 0.213; SE, 0.02), number memory (coefficient, 0.160; SE, 0.023), and prospective memory (coefficient, 0.341; SE, 0.024). Similar results were found in healthy controls. Among participants with bipolar disorder, handgrip strength was positively associated with improved visual memory (coefficient, −0.129; SE, 0.052; P = .01), reaction time (coefficient, −0.047; SE, 0.007; P < .001), prospective memory (coefficient, 0.262; SE, 0.088; P = .003), and reasoning (coefficient, 0.354; SE, 0.08; P < .001).
Conclusions and Relevance
Grip strength may provide a useful indicator of cognitive impairment in people with major depression and bipolar disorder. 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.
Firth J, Firth JA, Stubbs B, et al. Association Between Muscular Strength and Cognition in People With Major Depression or Bipolar Disorder and Healthy Controls. JAMA Psychiatry. 2018;75(7):740–746. doi:10.1001/jamapsychiatry.2018.0503
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