According to a multicenter study published in JAMA Psychiatry, handgrip strength is a reliable predictor of cognitive impairment among patients with bipolar disorder and major depression.
Using patient data from the United Kingdom Biobank, investigators performed a cross-sectional analysis of patients with major depression (n=22,699), bipolar disorder (n=1475), and healthy controls (n=85,893) to determine whether an association exists between handgrip strength and cognitive function.
A hydraulic hand dynamometer was used to measure muscular function across all patient groups. Investigators conducted assessment of cognitive function with a computerized task battery, which measured 5 total cognitive domains (visuospatial memory, reaction time, reasoning, prospective memory, numeric memory).
Linear mixed models demonstrated that maximal handgrip strength was a significant predictor of improved cognitive performance in each cognitive domain of the task battery (visual memory [coefficient, −0.146; standard error (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]; P <.001).
Handgrip strength was also a significant predictor of cognitive function in healthy controls (all domains P <.001). In addition, handgrip strength was significantly 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) in patients with bipolar disorder.
The inclusion of patients with a mean age of 55 years limits generalizability of the findings. Additionally, the results of this study report associations between handgrip strength and cognition rather than causal links between the 2 variables.
Investigators of this study explain that correlations “between handgrip strength and reaction time could potentially be explained by the rapid motor demands of reaction time tasks intuitively relating to muscular function of the hand, thus increasing the correlation between this cognitive domain and handgrip strength.”
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