Cognitive performance in adolescents with Delayed Sleep-Wake Phase Disorder: Treatment effects and a comparison with good sleepers

Long-lasting effects of disturbing the circadian rhythm or sleep in adolescence

Circadian rhythms are endogenous, near 24-hour rhythms that regulate a multitude of biological and behavioral processes across the diurnal cycle in most organisms. Over the lifespan, a bell curve pattern emerges in circadian phase preference (i.e. chronotype), with children and adults generally preferring to wake earlier and fall asleep earlier, and adolescents and young adults preferring to wake later and fall asleep later than their adult counterparts. This well-defined shift speaks to the variability of circadian rhythmicity over the lifespan and the changing needs and demands of the brain as an organism develops, particularly in the adolescent period. Indeed, adolescence is known to be a critical period of development during which dramatic neuroanatomical changes are occurring to allow for improved decision-making. Due to the large amount of re-structuring occurring in the adolescent brain, circadian disruptions during this period could have adverse consequences that persist across the lifespan. While the detrimental effects of circadian disruptions in adults have been characterized in depth, few studies have longitudinally assessed the potential long-term impacts of circadian disruptions during adolescence. Here, we will review the evidence that disruptions in circadian rhythmicity during adolescence have effects that persist into adulthood. As biological and social time often conflict in modern society, with school start times misaligned with adolescents' endogenous rhythms, it is critical to understand the long-term impacts of disrupted circadian rhythmicity in adolescence.

Delayed sleep phase disorder during the COVID-19 pandemic and its health implications

Circadian rhythm sleep disorders are alterations that are characterized by a shift in the sleep-wake cycle relative to day and night, such as the delayed sleep phase disorder (DSPD), which is a retard of at least 2 hours in the sleep start. Typically, the patient falls asleep after 2 a.m. and wakes up after 10 a.m. and with symptom of sleep onset insomnia. The prevalence of DSPD in young adults is 0.48%, increasing to 3.3% in adolescents. Interestingly, patients with COVID-19 infection report anxiety due to the intensive care unit lockdown and constant exposure to bright light. In addition, post-COVID patients have an increased risk of developing DSPD. For example, in adolescent post-COVID patients, the prevalence of DSPD increases to 63.3%. Patients with DSPD also have alterations in metabolic health, poor school performance, cognitive impairment, and a higher risk of developing other diseases. The objective of the present review is therefore to describe the characteristics of DSPD during the COVID-19 pandemic and to outline its possible implications for physical health (eg, metabolism) and mental health (eg, anxiety or depression).

Effectiveness of physical activity programs in enhancing sleep outcomes among adolescents: a systematic review

BACKGROUND

Adolescence is a developmental period characterised by rapid physical and psychological changes that heighten the risk for inadequate sleep. Fortunately, physical activity programs (PAPs) are an easy-to-do intervention that has been associated with improved sleep outcomes in different population groups. This systematic review aimed to provide evidence to support the effects of PAPs on sleep outcomes among apparently healthy adolescents.

METHODS

A systematic literature search was performed in online databases of PubMed, Cochrane Library, and PEDro for all dates up to April 2022. All relevant clinical trials reporting on the effects of PAPs on sleep among adolescents were included using a pre-defined inclusion/exclusion criterion (PROSPERO: CRD42020171852). The methodological quality of the included studies was assessed using 'specific checklists per design' (RCTs) provided by the Dutch Cochrane Centre. Qualitative synthesis was used to report the results of the review.

RESULTS

Two RCTs were included and analysed in the review. Both studies were of good methodological quality but lacked blinding. The PAPs in the reviewed studies included mainly aerobic exercises in the form of cross-country running in the mornings, SMS-delivered motivational messages to increase daily step counts, and use of a pedometer and step diaries. Sleep was measured both subjectively by means of sleep questionnaires and objectively using sleep electroencephalographic recordings. Nevertheless, qualitative synthesis is suggestive of an overall positive effect of PAPs on some sleep outcomes in adolescents, albeit with limited to moderate evidence.

CONCLUSION

PAPs appear to have a beneficial effect on some sleep outcomes among apparently healthy adolescents. Nevertheless, the body of evidence is currently scanty, thus warranting the need for more high-quality RCTs.

Sleep’s role in the development and resolution of adolescent depression

Two adolescent mental health fields — sleep and depression — have advanced largely in parallel until about four years ago. Although sleep problems have been thought to be a symptom of adolescent depression, emerging evidence suggests that sleep difficulties arise before depression does. In this Review, we describe how the combination of adolescent sleep biology and psychology uniquely predispose adolescents to develop depression. We describe multiple pathways and contributors, including a delayed circadian rhythm, restricted sleep duration and greater opportunity for repetitive negative thinking while waiting for sleep. We match each contributor with evidence-based sleep interventions, including bright light therapy, exogenous melatonin and cognitive-behaviour therapy techniques. Such treatments improve sleep and alleviate depression symptoms, highlighting the utility of sleep treatment for comorbid disorders experienced by adolescents.

Sleep problems are both a symptom and precursor of adolescent depression. In this Review, Gradisar et al. describe how the combination of adolescent sleep biology and psychology predisposes adolescents to develop depression, and describe interventions that improve sleep and depression symptoms in this population.

Circadian preference and intelligence - an updated meta-analysis

A large number of previous studies reported a link between circadian preference and psychometric intelligence with mixed results and various hypotheses about the source of this correlation. In this study, we aimed to update a previous meta-analysis about the correlation between circadian preference and intelligence. Our literature search identified a large number of new studies, resulting in an increase of over 100% in the number of studies and over 400% in the number of involved participants (total k = 30, total N = 11160) over the previous meta-analysis, sampling a much wider age range from children to adults in late middle age. Our meta-analysis revealed no significant link between morningness and intelligence (r = -0.008) when the entire sample was studied, and no evidence for publication bias. This overall effect, however, obscured the moderating effect of age. The morningness-intelligence correlation decreased with mean sample age (R² = 54%), ranging from a non-significant positive trend in children and adolescents to a significant negative correlation after young adulthood. Eveningness was positively correlated with intelligence (r = 0.056), but this finding is based on a more age-restricted sample and only reached significance with some model specifications. We hypothesize that the age-moderated correlation between circadian preference and intelligence reflects social effects, where more intelligent individuals are more able to adjust their daily schedules to their natural circadian rhythm.

Circadian Rhythm Disturbances in the Blind

PURPOSE OF REVIEW

Sleep timing, quantity, and quality are controlled by homeostatic and circadian systems. Circadian clock systems are present in all cells and organs and their timing is determined by a transcriptional-translational feedback loop of circadian genes. Individual cellular clocks are synchronized by the central body clock, situated in the suprachiasmatic nucleus, which communicates with them through humoral and neural signals including melatonin. The circadian system controls both the circadian period: (i.e., the length of the intrinsic clock), but also the circadian phase (i.e., the clock timing). An important determinant of the circadian system is light exposure. In most humans, the circadian period is slightly longer than 24 h and without regular resetting it tends to drift, leading to progressively later bedtimes and wake times and a tendency to cycle though periods of normal and abnormal sleep. Blind patients are thus at an increased risk of abnormal circadian function. The purpose of this article is to review recent research and clinical management of circadian rhythm disorders in blind patients.

RECENT FINDINGS

Blind patients can present delayed and advanced sleep phase disorders but the most common abnormality in totally blind patients without light perception is non-24-hour sleep-wake disorder (N24SWD). This is rare in the general population but may affect up to 50% of blind patients without light perception. The diagnosis of a circadian rhythm disorder in the blind is complex. New screening tools have been developed but actigraphy and repeated melatonin profiles over 24 h remain essential. Circadian disorders in the blind are frequent, especially in the patients without light perception. They require accurate diagnosis in order to target treatment. Determining the precise nature of a sleep disorder in blind patients with a suspected circadian rhythm abnormality is complex and requires a detailed clinical history with sleep diaries and the use of actigraphy and melatonin profiles.