Straight From the Heart:Does Individual Resting Heart Rate Variability Moderate the Effect of Sleep Deprivation on Social Interaction?

Objective: Sleep is an important part of the human experience, and sleep disturbances are common. A consequence of sleep loss is decreased social interactions, which are crucial for well-being. Since individuals differ in their reaction to sleep loss, investigating potential risk factors and protective mechanisms facilitates public health knowledge. One promising biomarker for adaptability and resilience is heart-rate variability (HRV), which may offer clues as to why individuals handle the effects of sleep loss differently. This thesis examines whether HRV moderates the effects of sleep deprivation on social interaction. Method: Using a within-subject, crossover and counterbalanced experimental design, participants (N = 48) were tested multiple times: after two nights of sleep saturation (nine hours) and after two nights of sleep deprivation (four hours). Instigation and duration of social interaction was measured during a meal break from the main testing protocol. HRV was measured at baseline, after sleep saturation. Results: There were no significant effects of HRV, sleep condition, or their interaction on overall social interaction duration or likelihood of social interaction instigation. However, age was a significant predictor of instigation, with older participants more likely to initiate conversation. Conclusions: Contrary to previous findings, sleep deprivation did not reduce social interaction, and HRV was not associated with social interaction. These results may reflect true null effects or may be shaped by the specific social context and measurement approach. Future work may want to examine HRV during real-time interaction and consider broader motivational and contextual influences.