Class III obesity is associated with increased risk for cognitive impairment. Though hypothesized to be partially attributable to sedentary time (ST), past research examining the association between ST and cognitive function has produced mixed findings. One possible explanation is that studies do not typically account for the highly correlated and almost inverse relationship between ST and light intensity physical activity (LPA), such that ST displaces time engaging in LPA. Therefore, we aimed to evaluate whether: (1) higher ST-to-LPA time ratio associates with poorer performance across multiple cognitive domains in patients with Class III obesity seeking bariatric surgery; and (2) the associations differ by sex.

Participants (N = 121, 21-65 years of age, BMI > 40 kg/m2) scheduled for either Roux-en-Y Gastric Bypass (RYGB) or Sleeve Gastrectomy (SG) completed the NIH Toolbox, a computerized neuropsychological assessment battery and wore a waist-mounted ActiGraph monitor during waking hours for 7 days to measure minutes/day spent in ST, LPA, and moderate-to-vigorous physical activity (MVPA). A ratio of time spent in ST-to-LPA was calculated by dividing the percentage of daily wear time spent in sedentary behavior (SB) by the percentage of daily wear time spent in LPA.

On average, participants (mean age = 43.22 years old and BMI = 45.83 kg/m2) wore the accelerometer for 909±176 minutes/day and spent 642±174 minutes/day in ST, 254±79 minutes/day in LPA, and 14±13 minutes/day in MVPA. Mean daily ST-to-LPA time ratio was 2.81 ± 1.3 (0.73-7.11). Overall, bivariate Pearson correlations found no significant relationships between LPA and cognitive performance on any of the NIH Toolbox subtests (r values = -.002 to -.158, all p values >.05). Additionally, bivariate Pearson correlations also found no significant relationships between daily ST-to-LPA time ratio and cognitive performance on any of the subtests (r values = .003 to .108, all p values >.05). However, higher ST-to-LPA was associated with lower scores on the Dimensional Change Card Sort Test in women (r = -.26, p = .01).

Results showed that participants’ mean daily time spent in ST was 2.5 times higher than that spent in LPA and a higher ratio of ST-to-LPA was associated with poorer set-shifting in women with Class III obesity. Future studies should look to clarify underlying mechanisms, particularly studies examining possible sex differences in the cognitive benefits of PA. Similarly, intervention studies are also needed to determine if increasing LPA levels for individuals with Class III obesity would lead to improved cognitive performance by means of reducing ST.