Abstract
Many American adolescents and adults report that they are not meeting sleep duration recommendations. Although insufficient sleep duration can occur due to factors outside an individual's direct control, many individuals choose to restrict their own sleep. The theory of planned behaviour (TPB) offers a framework to study this phenomenon. Recent research efforts have used the TPB to study sleep and have demonstrated success predicting sleep-related intentions and behaviour but have failed to consider volitional sleep behaviour or consider between- and within-person differences. The present study used an intensive longitudinal design to test how constructs of the TPB relate to nightly sleep opportunity. Healthy college students (N = 79) participated in a weeklong study in which they completed four ecological momentary assessment signals per day that measured their attitudes, subjective norms, perceived behavioural control, and intentions relating to their nocturnal sleep opportunity. Participants wore an actiwatch each night of the study to measure their sleep opportunity. Mixed linear models found that both intentions and perceived behavioural control were significant predictors of subsequent sleep opportunity, and that perceived behaviour control was the strongest within-day predictor of intentions. Results demonstrate that within-person changes in perceived behavioural control and intentions predict subsequent sleep opportunity and provide insight into the potential refinement of sleep promotion efforts.