Delay discounting and response disinhibition moderate associations between actigraphically measured sleep parameters and body mass index.

Previous research suggests that the sleep-obesity association varies significantly across individuals. This study examined the associations between actigraphically measured sleep parameters and body mass index and hypothesized that the associations would be stronger in individuals with greater delay discounting, the devaluation of future rewards and response disinhibition and the difficulty in withholding previously rewarded responses. Seventy-eight college students carried a wrist-worn actigraph and completed diaries reporting bedtime, wake time and covariates including physical activity, alcohol and caffeine consumption, daytime nap duration and perceived stress for 7 days and completed the delay discounting and go/no-go response disinhibition tasks. Their height and weight were measured. Only bedtime variability was significantly associated with body mass index in the main effect model controlling for all covariates (B = 0.03, P = 0.001). Delay discounting moderated associations of bedtime (B = 0.03, P < 0.001), sleep duration variability (B = 0.05, P = 0.002), bedtime variability (B = 0.03, P = 0.002) and wake time variability (B = 0.02, P < 0.001) with body mass index; these associations were significant only when the delay discounting rate was high. Response disinhibition moderated the association between bedtime variability and body mass index in a similar pattern (B = 0.01, P = 0.004). The findings suggest that, using actigraphy measures of sleep, circadian desynchrony rather than sleep duration is a risk factor for higher body mass index. The findings support the hypothesis that delay discounting and response disinhibition moderate the associations between sleep and body mass index. Delay discounting and response disinhibition might characterize individuals who are vulnerable to the influence of circadian desynchrony on weight.