Sleepiness is a signal to go to bed: data and model simulations

Abstract

Study Objectives Assess the validity of a subjective measure of sleepiness as an indicator of sleep drive by quantifying associations between intra-individual variation in evening sleepiness and bedtime, sleep duration, and next morning and subsequent evening sleepiness, in young adults. Methods Sleep timing and sleepiness were assessed in 19 students in late autumn and late spring on a total of 771 days. Karolinska Sleepiness Scales (KSS) were completed at half-hourly intervals at fixed clock times starting four hours prior to participants’ habitual bedtime, and in the morning. Associations between sleepiness and sleep timing were evaluated by mixed model and non-parametric approaches and simulated with a mathematical model for the homeostatic and circadian regulation of sleepiness. Results Intra-individual variation in evening sleepiness was very large, covering four or five points on the 9-point KSS scale, and was significantly associated with subsequent sleep timing. On average, a one point higher KSS value was followed by 20 min earlier bedtime, which led to 11 min longer sleep, which correlated with lower sleepiness next morning and following evening. Associations between sleepiness and sleep timing were stronger in early compared to late sleepers. Model simulations indicated that the directions of associations between sleepiness and sleep timing are in accordance with their homeostatic and circadian regulation, even though much of the variance in evening sleepiness and details of its time course remain unexplained by the model. Conclusion Subjective sleepiness is a valid indicator of the drive for sleep which, if acted upon, can reduce insufficient sleep.

Circadian rhythmicity of pain sensitivity in humans

“…We assessed the effect of time-of-day on pain sensitivity, by measuring heat pain every two hours during the 34 h of constant routine. In accordance with the current view that two main processes regulate sleep 35 , and in agreement with studies showing that subjective sleepiness 13,36 and physiological functions (such as executive functions 37 ) and cortical brain responses (measured by EEG 14 and fMRI 8 ) are influenced by both sleep pressure and the circadian timing system, we then modeled the effect of time on pain with an additive mathematical model including a linear component (sleep-related homeostatic drive -process S) and a sinusoidal component (circadian drive -process C) 13 .…”

Extracting Circadian and Sleep Parameters from Longitudinal Data in Schizophrenia for the Design of Pragmatic Light Interventions

“…Our method may be generalizable to other disorders, for example those with unipolar depression, bipolar disorder or dementia. 44 However, we also recognize that modeling between-day variability in sleep timing, for example as in, 45 and short-term alerting effects of light is pending. Further data are also required to examine the extent to which increasing light alters sleep duration.…”

Self-Reported Sleep Disturbance is an Independent Predictor of All-Cause Mortality and Respiratory Disease Mortality in US Adults: A Population-Based Prospective Cohort Study

“…Then, univariate Cox regression models were used to quantify the risk of self-reported sleep disturbance with HR of 1.47 (95% CI: 1.36-1.59) for all-cause mortality, HR of 1.32 (1. 13 S1). Univariate analysis of other covariates was also summarized in Supplementary Table S1.…”

“…Moreover, to confirm the diagnosis of a certain type of sleep disorder, a series of questionnaires and examinations (e.g., polysomnography) ( 11 , 12 ) are necessary, which limits the evaluation of sleep health in the general population. On the other hand, subjective sleepiness is valid to indicate the drive for sleep ( 13 ) and is more effective in predicting voluntary decreases in social activity than sleep duration ( 10 ). Excessive daytime sleepiness is associated with high risks of cardiovascular mortality ( 14 ).…”