Sleep Disturbance and Its Association With Sluggish Cognitive Tempo and Attention in Pediatric Brain Tumor Survivors.

Background: Pediatric brain tumor (PBT) survivors are at risk for developing sleep disturbances. While in other pediatric populations sleep disturbance has been associated with worse cognitive functioning, it is unclear to what extent this relationship generalizes to PBT survivors. The aim of the current study was to assess the relationship between sleep disturbance and aspects of cognition, including sluggish cognitive tempo (SCT) as well as attention and working memory. Materials and Methods: Eighty-three PBT survivors 6-18 years of age who were at least 3 months post-treatment were included in the present cross-sectional study. Level of sleep disturbance was measured as a composite score reflecting various sleep problems as rated by caregivers. Cognitive measures included caregiver-ratings of sluggish cognitive tempo and attention problems, as well as performance-based cognitive measures assessing attention and executive functioning. Hierarchical regression analysis was used to assess associations between sleep and cognition. Results: Of all caregivers, 32.5% reported one or more sleep disturbances as "very/often true" and over 68% of caregivers rated at least one sleep-related item as "somewhat true." Of all cognitive variables, scores were most frequently impaired for SCT (30%). A higher level of sleep disturbance was associated with worse SCT and parent-rated attention problems. Associations between sleep and performance-based cognitive measures assessing attention and working memory were not statistically significant. Conclusion: Findings of the current study highlight the importance of further investigation into the relationship between sleep and cognition in PBT survivors, which may assist efforts to maximize cognitive outcome and health-related quality of life in PBT survivors. The current study additionally suggests further investigation of SCT in this population is warranted, as it may be more sensitive to detecting possible associations with sleep disturbance relative to discrete measures that assess cognitive performance under ideal circumstances.

Substance abuse as a dynamical disease: evidence and clinical implications of nonlinearity in a time series of daily alcohol consumption.

Several authors have suggested that chaos theory, the study of nonlinear dynamics and the application of the knowledge gained to natural and social phenomena, might yield insight into substance-related disorders. In this article, we examine the dynamics of substance abuse by fitting a nonlinear model to a time series of the amount of alcohol, which an adult male with a diagnosis of substance abuse consumed on a daily basis. The nonlinear model shows a statistically superior fit when compared to a linear model. We then use the model to explore a question that is pertinent to the treatment of substance abuse, whether controlled drinking or abstinence is a preferred strategy for maintaining sobriety.

Multiscale nonlinearity in a time series of weekly alcohol intake.

Several authors have discussed the possibility that nonlinear dynamics might clarify substance abuse and chemical dependence. Nonlinear dynamical structure implies the possibility of oscillatory dynamics and high sensitivity to external perturbation. In this single-subject case study we analyzed the alcohol intake of a substance-abusing participant over a period of about five years using nonlinear time series analysis. The intake is measured in ounces per week and ounces per four weeks--approximately one month--yielding time series at two different time scales. We present statistical evidence that the participant's alcohol intake is nonlinear on both weekly and monthly time scales. We then discuss the implications of this multiscale nonlinearity for our understanding of substance abuse.