Neural mechanisms that promote food consumption following sleep loss and social stress: an fMRI study in adolescent girls with overweight/obesity.

STUDY OBJECTIVES: Insufficient sleep and social stress are associated with weight gain and obesity development in adolescent girls. Functional magnetic resonance imaging (fMRI) research suggests that altered engagement of emotion-related neural networks may explain overeating when under stress. The purpose of this study is to explore the effects of acute sleep restriction on female adolescents' neural responding during social evaluative stress and their subsequent eating behavior. METHODS: Forty-two adolescent females (ages 15-18 years) with overweight or obesity completed a social stress induction task in which they were told they would be rated by peers based on their photograph and profile. Participants were randomly assigned to one night of sleep deprivation or 9 h of sleep the night before undergoing fMRI while receiving positive and negative evaluations from their peers. After which, subjects participated in an ad libitum buffet. RESULTS: Sleep deprived, relative to nondeprived girls had distinct patterns of neural engagement to positive and negative evaluation in anterior, mid, and posterior aspects of midline brain structures. Moreover, a sleep deprivation-by-evaluation valence-by-caloric intake interaction emerged in bilateral dorsal anterior cingulate. Among sleep deprived girls, greater engagement during negative, but not positive, feedback was associated with lower caloric intake. This was not observed for nonsleep deprived girls. CONCLUSIONS: Results suggest an interaction between acute sleep loss and social evaluation that predicts emotion-related neural activation and caloric intake in adolescents. This research helps to elucidate the relationship between sleep loss, social stress, and weight status using a novel health neuroscience model.

Does iPhone night shift mitigate negative effects of smartphone use on sleep outcomes in emerging adults?

OBJECTIVES: Apple's iPhone Night Shift feature purports to reduce short-wavelength light emissions and improve sleep. We aimed to investigate these claims by comparing emerging adults' sleep outcomes associated with smartphone use before bed with iPhone's Night Shift enabled to two comparison conditions (iPhone use with no Night Shift, no iPhone use). DESIGN: Participants were randomly assigned to one of three conditions specifying iPhone use during the hour preceding bedtime for seven consecutive nights: iPhone use with Night Shift enabled; iPhone use with Night Shift disabled; and no phone use. SETTING: Participants were recruited from a western undergraduate university. PARTICIPANTS: A sample of 167 emerging adults (ages 18-24; 71.3% female) with iPhones participated in the study. MEASUREMENTS: Sleep outcomes (sleep latency, duration, efficiency and wake after sleep onset) were tracked using wrist-worn accelerometers. RESULTS: There were no significant differences in sleep outcomes across the three experimental groups. Post-hoc exploratory stratified analyses revealed a significant main effect of phone condition on sleep efficiency (P = .014) and WASO (P = .013) for participants averaging more than 6.8 hours of sleep per night, with the no phone condition demonstrating the best sleep outcomes. For those averaging less than 6.8 hours of sleep, there was no effect of phone condition on sleep outcomes. CONCLUSIONS: Across our full study sample, there were no differences in sleep outcomes attributable to Night Shift. For individuals who regularly obtained adequate sleep, abstaining from screen use resulted in better quality sleep than did phone use with Night Shift enabled.