Dim light, sleep tight, and wake up bright - Sleep optimization in athletes by means of light regulation.

Despite an elevated recovery need, research indicates that athletes often exhibit relatively poor sleep. Timing and consolidation of sleep is driven by the circadian system, which requires periodic light-dark exposure for stable entrainment to the 24-hour day, but is often disturbed due to underexposure to light in the morning (e.g. low-level indoor lighting) and overexposure to light in the evening (e.g. environmental and screen-light). This study examined whether combining fixed sleep schedules with light regulation leads to more consolidated sleep. Morning light exposure was increased using light-emitting goggles, whereas evening light exposure was reduced using amber-lens glasses. Using a within-subject crossover design, twenty-six athletes (14 female, 12 male) were randomly assigned to start the intervention with the light-regulation-week or the no light-regulation-week. Sleep was monitored by means of sleep diaries and actigraphy. Due to low protocol adherence regarding the fixed sleep-wake schedules, two datasets were constructed; one including athletes who kept a strict sleep-wake schedule (N = 8), and one that also included athletes with a more lenient sleep-wake schedule (N = 25). In case of a lenient sleep-wake schedule, light regulation improved self-reported sleep onset latency (Δ SOL = 8 min). This effect was stronger (Δ SOL = 17 min) and complemented by enhanced subjective sleep quality in case of a strict sleep-wake schedule. None of the actigraphy-based estimates differed significantly between conditions. To conclude, light regulation may be considered a potentially effective strategy to improve subjective sleep, but less obtrusive methods should be explored to increase protocol compliance.

Restricting short-wavelength light in the evening to improve sleep in recreational athletes - A pilot study.

Sleep is crucial for recovery and skill acquisition in athletes. Paradoxically, athletes often encounter difficulties initiating and maintaining sleep, while having sufficient sleep opportunity. Blue (short-wavelength) light as emitted by electronic screens is considered a potential sleep thief, as it suppresses habitual melatonin secretion. The current study sought to investigate whether blocking short-wavelength light in the evening can improve sleep onset latency and potentially other sleep parameters among recreational athletes. The study had a within-subject crossover design. Fifteen recreational athletes, aged between 18 and 32 years (12 females, 3 males), were randomly assigned to start the intervention period with either the light restriction condition (LR; amber-lens glasses), or the no-light restriction condition (nLR; transparent glasses). Sleep hygiene practices, actigraphy and diary-based sleep estimates were monitored during four consecutive nights within each condition. Sleep hygiene practices did not significantly differ between conditions. Results indicate that blocking short-wavelength light in the evening, as compared to habitual light exposure, significantly shortened subjective sleep onset latency (Δ = 7 min), improved sleep quality (Δ = 0.6; scale 1-10), and increased alertness the following morning. Actigraphy-based sleep estimates showed no significant differences between conditions. Blocking short-wavelength light in the evening by means of amber-lens glasses is a cost-efficient and promising means to improve subjective sleep estimates among recreational athletes in their habitual home environment. The relatively small effects of the current study may be strengthened by additionally increasing morning- and daytime light exposure and, potentially, by reducing the alerting effects of media use before bedtime.

Train hard, sleep well? Perceived training load, sleep quantity and sleep stage distribution in elite level athletes.

OBJECTIVES: Sleep is essential for recovery and performance in elite athletes. While it is generally assumed that exercise benefits sleep, high training load may jeopardize sleep and hence limit adequate recovery. To examine this, the current study assessed objective sleep quantity and sleep stage distributions in elite athletes and calculated their association with perceived training load. DESIGN: Mixed-methods. METHODS: Perceived training load, actigraphy and one-channel EEG recordings were collected among 98 elite athletes during 7 consecutive days of regular training. RESULTS: Actigraphy revealed total sleep durations of 7:50±1:08h, sleep onset latencies of 13±15min, wake after sleep onset of 33±17min and sleep efficiencies of 88±5%. Distribution of sleep stages indicated 51±9% light sleep, 21±8% deep sleep, and 27±7% REM sleep. On average, perceived training load was 5.40±2.50 (scale 1-10), showing large daily variability. Mixed-effects models revealed no alteration in sleep quantity or sleep stage distributions as a function of day-to-day variation in preceding training load (all p's>.05). CONCLUSIONS: Results indicate healthy sleep durations, but elevated wake after sleep onset, suggesting a potential need for sleep optimization. Large proportions of deep sleep potentially reflect an elevated recovery need. With sleep quantity and sleep stage distributions remaining irresponsive to variations in perceived training load, it is questionable whether athletes' current sleep provides sufficient recovery after strenuous exercise.

Validation of Photoplethysmography-Based Sleep Staging Compared With Polysomnography in Healthy Middle-Aged Adults.

Study Objectives: To compare the accuracy of automatic sleep staging based on heart rate variability measured from photoplethysmography (PPG) combined with body movements measured with an accelerometer, with polysomnography (PSG) and actigraphy. Methods: Using wrist-worn PPG to analyze heart rate variability and an accelerometer to measure body movements, sleep stages and sleep statistics were automatically computed from overnight recordings. Sleep-wake, 4-class (wake/N1 + N2/N3/REM) and 3-class (wake/NREM/REM) classifiers were trained on 135 simultaneously recorded PSG and PPG recordings of 101 healthy participants and validated on 80 recordings of 51 healthy middle-aged adults. Epoch-by-epoch agreement and sleep statistics were compared with actigraphy for a subset of the validation set. Results: The sleep-wake classifier obtained an epoch-by-epoch Cohen's κ between PPG and PSG sleep stages of 0.55 ± 0.14, sensitivity to wake of 58.2 ± 17.3%, and accuracy of 91.5 ± 5.1%. κ and sensitivity were significantly higher than with actigraphy (0.40 ± 0.15 and 45.5 ± 19.3%, respectively). The 3-class classifier achieved a κ of 0.46 ± 0.15 and accuracy of 72.9 ± 8.3%, and the 4-class classifier, a κ of 0.42 ± 0.12 and accuracy of 59.3 ± 8.5%. Conclusions: The moderate epoch-by-epoch agreement and, in particular, the good agreement in terms of sleep statistics suggest that this technique is promising for long-term sleep monitoring, although more evidence is needed to understand whether it can complement PSG in clinical practice. It also offers an improvement in sleep/wake detection over actigraphy for healthy individuals, although this must be confirmed on a larger, clinical population.

Human circadian phase estimation from signals collected in ambulatory conditions using an autoregressive model.

Phase estimation of the human circadian rhythm is a topic that has been explored using various modeling approaches. The current models range from physiological to mathematical, all attempting to estimate the circadian phase from different physiological or behavioral signals. Here, we have focused on estimation of the circadian phase from unobtrusively collected signals in ambulatory conditions using a statistically trained autoregressive moving average with exogenous inputs (ARMAX) model. Special attention has been given to the evaluation of heart rate interbeat intervals (RR intervals) as a potential circadian phase predictor. Prediction models were trained using all possible combinations of RR intervals, activity levels, and light exposures, each collected over a period of 24 hours. The signals were measured without any behavioral constraints, aside from the collection of saliva in the evening to determine melatonin concentration, which was measured in dim-light conditions. The model was trained and evaluated using 2 completely independent datasets, with 11 and 19 participants, respectively. The output was compared to the gold standard of circadian phase: dim-light melatonin onset (DLMO). The most accurate model that we found made use of RR intervals and light and was able to yield phase estimates with a prediction error of 2 ± 39 minutes (mean ± SD) from the DLMO reference value.

Increased skin temperature in Alzheimer's disease is associated with sleepiness.

The 24-h rhythms in sleep and temperature both change in Alzheimer's disease (AD). Characteristic changes consist of a more fragmented diurnal sleep profile with frequent nocturnal awakenings and daytime sleepiness, as well as a reduction in the amplitude of the 24-h rhythm in core body temperature (CBT). Although the 24-h rhythm in CBT is to a large extent the result of a 24-h rhythm in heat loss from the skin caused by pronounced changes in skin blood flow and consequently skin temperature (Ts), changes in the diurnal skin temperature profile in AD as compared to normal aging have remained unexplored. Because recent work indicates a causal contribution of fluctuations in skin temperature to daytime sleepiness and nocturnal sleep depth, the present study aimed to investigate the skin temperature rhythm in AD and its association with daytime sleepiness and nocturnal sleep. Ambulatory recorders were used to estimate sleep and 24-h rhythms in skin temperature in 55 AD patients and 26 matched non-demented elderly controls. Subjective sleep and daytime sleepiness were obtained using questionnaires. The results indicate that AD patients had a significantly higher daytime proximal skin temperature (PST) than elderly controls. In both AD patients and elderly controls, an elevated daytime PST was associated with more daytime sleepiness. The findings suggest a deficient downregulation of daytime proximal skin blood flow that might contribute to daytime sleepiness. Because daytime sleepiness contributes to cognitive dysfunction in AD, further research into the underlying mechanisms and possible reversibility is warranted.

Discrepancy between subjective and objective sleep disturbances in early- and moderate-stage Alzheimer disease.

OBJECTIVE: Sleep disturbances such as nocturnal awakenings frequently occur in demented elderly persons and can contribute to depression, cognitive impairment, and caregiver burden. Recognizing sleep disturbances at an early stage of the disease progress is a first prerequisite of intervention and monitoring of progress. This study aimed to investigate the reliability of subjective sleep reports in early- and moderate-stage Alzheimer dementia (AD), by investigating whether they differ from matched healthy normal comparison groups with respect to the discrepancy of subjective and objective sleep estimates. MEASUREMENTS: Subjective sleep was assessed using the Pittsburgh Sleep Quality Index, the Sleep Disorders Questionnaire, and the Athens Insomnia Scale. Objective sleep was estimated using actigraphy. RESULTS: As compared with the normal comparison group (N = 26), AD patients (N = 55) complained less of insomnia, while their objective sleep estimates indicated, in fact, more disturbed sleep, including a longer sleep onset latency and a lower sleep efficiency. Regression analyses aimed at predicting actigraphic sleep parameter estimates from their subjective counterparts showed significant predictive value of only very few subjective sleep parameters. Subjective reports of both patients and the normal comparison group had significant value in predicting actigraphic indices of total sleep time and bedtime. In addition, subjective reports of the normal comparison group, but not of patients, were of value to predict actigraphic indices of sleep onset latency, average sleep bout duration, and sleep efficiency. CONCLUSION: The results show that the value of sleep questionnaires is limited in early- and moderate-stage AD. Actigraphy may be essential to ensure that sleep problems do not go undetected and untreated.

Prevention of depression and sleep disturbances in elderly with memory-problems by activation of the biological clock with light--a randomized clinical trial.

BACKGROUND: Depression frequently occurs in the elderly and in patients suffering from dementia. Its cause is largely unknown, but several studies point to a possible contribution of circadian rhythm disturbances. Post-mortem studies on aging, dementia and depression show impaired functioning of the suprachiasmatic nucleus (SCN) which is thought to be involved in the increased prevalence of day-night rhythm perturbations in these conditions. Bright light enhances neuronal activity in the SCN. Bright light therapy has beneficial effects on rhythms and mood in institutionalized moderate to advanced demented elderly. In spite of the fact that this is a potentially safe and inexpensive treatment option, no previous clinical trial evaluated the use of long-term daily light therapy to prevent worsening of sleep-wake rhythms and depressive symptoms in early to moderately demented home-dwelling elderly. METHODS/DESIGN: This study investigates whether long-term daily bright light prevents worsening of sleep-wake rhythms and depressive symptoms in elderly people with memory complaints. Patients with early Alzheimer's Disease (AD), Mild Cognitive Impairment (MCI) and Subjective Memory Complaints (SMC), between the ages of 50 and 75, are included in a randomized double-blind placebo-controlled trial. For the duration of two years, patients are exposed to approximately 10,000 lux in the active condition or approximately 300 lux in the placebo condition, daily, for two half-hour sessions at fixed times in the morning and evening. Neuropsychological, behavioral, physiological and endocrine measures are assessed at baseline and follow-up every five to six months. DISCUSSION: If bright light therapy attenuates the worsening of sleep-wake rhythms and depressive symptoms, it will provide a measure that is easy to implement in the homes of elderly people with memory complaints, to complement treatments with cholinesterase inhibitors, sleep medication or anti-depressants or as a stand-alone treatment. TRIAL REGISTRATION: ISRCTN29863753.

Beneficial effect of transcranial magnetic stimulation on sleep in Parkinson's disease.

Sleep disorders are common in Parkinson's disease (PD) and have profound negative influences on quality of life. Sleep structure in healthy participants can be changed by repetitive transcranial magnetic stimulation (rTMS), but this has never been studied systematically in PD. Therefore, we characterized sleep in PD patients and examined effects of rTMS using a combination of actigraphy and a pressure sensitive pad. Thirteen PD patients received 5 Hz rTMS over the motor or parietal cortex. Actigraphic sleep estimates were obtained before, during and after rTMS, as well as compared with 8 healthy, age-matched controls. Motor symptoms and mood were evaluated before and after rTMS. Mixed-model regression analyses indicated that PD patients slept shorter (350 +/- 17 vs. 419 +/- 24 min., P = 0.02), more fragmented (fragmentation index 41 +/- 4 vs. 22 +/- 2, P = 0.0004) and had a lower sleep efficiency (77 +/- 2 vs. 86 +/- 2%, P = 0.002) and longer nocturnal awakenings (3.4 +/- 0.2 vs. 2.3 +/- 0.2 min., P = 0.003) than healthy controls. rTMS over the parietal, but not over the motor cortex improved sleep fragmentation (P = 0.0002) and sleep efficiency (P = 0.0002) and reduced the average duration of nocturnal awakenings (P = 0.02). No change of motor symptoms or mood was observed. Disturbed sleep in PD patients may partly be reversed by parietal rTMS, without affecting motor symptoms or mood.