Grip strength may provide indication of cognitive impairment in those with bipolar disorder and major depression, according to a cross-sectional analysis of a multicenter, population-based study published in JAMA Psychiatry.
The study used clinically validated measures to select 110,067 participants in the UK Biobank with major recurrent depression (moderate or severe) or bipolar disorder (type I or type II) and healthy controls (no indication of past or present mood disorders). From February 13, 2005 to October 1, 2010, these participants underwent 5 computerized tasks (number memory, prospective memory, reaction time, reasoning, and visual memory) designed to test cognitive function, in addition to handgrip dynamometry to measure muscular function. Generalized linear mixed models were then used to assess the association between them, controlling for age, body weight, educational level, geographic region, and sex.
Results from a cross-section analysis of the data, conducted between August 3 and August 18, 2017, included 22,699 participants with major recurrent depression, 1475 with bipolar disorder, and 85,893 healthy controls. On all 5 cognitive tasks, participants with major depression showed significant positive associations (P <.001) between handgrip strength and cognitive performance, with healthy controls performing similarly. Positive associations were found in 4 of the 5 cognitive tasks for participants with bipolar disorder: prospective memory (P =.003), reaction time (P <.001), reasoning (P< .001), and visual memory (P =.01).
Although there is a known association between reduced physical fitness and cognitive impairment in those with mental illness, no studies to date have considered the association between muscular strength and cognition. Thus, this study intended to determine the association between maximal handgrip strength, an objective physical fitness measure, and cognitive performance.
These results suggest that, for those with major depression or bipolar disorder, maximal grip strength may be an indicator of cognitive impairment, though the research is not without limitations. Further studies should consider causality and the effects of interventions intended to improve muscular fitness.
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 [published online April 18, 2018]. JAMA Psychiatry. doi:10.1001/jamapsychiatry.2018.0503