Sleep Quality + Sleep Disturbances

What type of circadian rhythm is sleep? 

The most prominent one. 

How long do we spend asleep in our lives? 

36% (approx 1/3). 

What occurs during sleep? 

Brain undergoes many changes during sleep – some regions being more active when awake 

Which stimulants are used to fight sleep?

Caffeine and nicotine. 

Which sedatives induce sleep? 

Drugs and alcohol.

 

What does a lack of sleep cause? (5) 

Severe mood fluctuations, impaired memory, poor judgement, brain drives cravings for carbs and sugary foods for weight gain, addiction to stimulants.

Why do we sleep?

Repair – supported by fluctuation of housekeeping hormones during night. Conservation of resources – replenish and generate energy store for more active periods, brain function – memory consolidation (structuring/storing memories), info processing, learning – sleep enhances learning and recall, 

How do day and night cycles affect sleep?

Brain ‘locks onto’ this and synchronises our physiological and behavioural activity – in a diurnal manner for humans 

What should this regulation result in?

A robust sleep-wake cycle. However, this doesn’t always work.

What can sleep rejection lead to?

+100% heart disease, 200% cancer, 20% death risk and obesity.

What are consequences of shift work? 

Blood sugar imbalances and diabetes inhibited mental performance, increased risk of injury and accidents, hormone imbalances, weight gain, digestive disorders, depression, anxiety, chronic fatigue.

What are circadian rhythm sleep disorders?

Jet lag, shiftwork, advanced/delayed sleep disorder.

What can circadian rhythm sleep disorders lead to?

Depression, cognitive decline, hypoinsulinaemia, insulin resistance, chronic stress, autoimmunity, hypertension, ibd flare, obesity, metabolic syndrome. 

What is the primary signalling cue used by circadian clock in regulating/synchronising sleep? 

Sunlight, any deviation from natural sunlight can have bad consequences to sleep and mood.

What is sleep pressure? 

Homeostatic, biological need for sleep that builds the longer you’re awake. Non-negotiable biological signal. Ignoring it only creates a deficit that must eventually be paid back with sleep.

What is seasonal affective disorder (SAD)?

Depressed in winter, stops in summer. Can be fixed with light box.

What happens to the clock as we age? 

Sleep patterns change. Cells become less synchronised causing fluctuations. 

How can circadian rhythms be applied to health?

Investigative tools and therapies; biomarkers – hormonal, genetic, light therapy e.g SAD, CBT-I. 

How is sleep measured? 

Subjective, behavioural, physiological methods

What is the subjective measurement of sleep?

Perception based. Sleep diaries, questionnaires (PSQI etc) and interviews. Outputs of perceived sleep quality and daytime impact. Biased and inaccurate recall.

What is the behavioural measurement of sleep?

Movement-based. Actigraphy (wearables) and consumer sleep trackers. Output is sleep timing and sleep-wake patterns. 

What is physiological measurement?

Gold standard. Polysomnography (PSG), EEG, EOG, EMG recordings. Output is sleep stages (REM/NREM), brain and body physiology. Expensive, intrusive, not scalable. 

Why was the Pittsburgh Sleep Quality Index (PSQI) developed?

To provide reliable, valid and standardised measure of sleep quality, to discriminate between good and poor sleepers, to provide an index that is easy for subjects to use and for clinicians and researchers to interpret, to provide brief, clinically useful assessment of a variety of sleep disturbances that might affect sleep quality. 

What is the PSQI?

19 self-report items + 5 partner-rated, not scored. Covers 7 components: Subjective sleep quality, sleep latency, sleep duration, sleep efficiency, sleep disturbances, sleep medication use, daytime dysfunction. Produces a global score (0-21). Assessment timeframe: past 1 month.

Where were items in PSQI derived? 

Clinical intuition and experience with sleep disorder patients, a review of previous sleep quality questionnaires reported in literature, clinical experience with the instrument during 18mths of field testing. 

How does PSQI assess sleep quality?

Provides frequency or duration of specific problems that may lead a patient to seek help. Can indicate severity of particular problem at present time. Administering PSQI on 2 occasions separated by 1mth allows for discrimination of most transient and persistent disturbances. 

What were the PSQI sampling groups?

Good sleepers, poor sleepers and poor sleepers with clinical sample of physician-referred outpatients.

How was the PSQI validated?

All subjects evaluated with routine polysomnography following a medication-free interval of at least 2 weeks. All subjects studied with routine sleep montage, including electroencephalographic electro-oculographic (EOG), and electromyographic (submental) leads.

What is statistical analysis for PSQI?

Descriptive stats and ANOVA. Internal homogeneity of seperate items was assessed using Cronbach's alpha statistic and corrected component-total correlation coefficient. Pearson product-moment correlations were also used to correlate component and item scores with the PSQI global score. Test-retest reliability assessed with paired t test and pearson product-moment correlations for PSQI global score. ANCOVA used to compare patient groups for PSQI global and component scores. 

What are strengths of PSQI? 

Simple, quick, 5-10mins, low cost, no equipment, standardised scoring, good test-retest reliability, validated across many populations, captures multidimensional sleep experience. Has global reach. 

What are weaknesses of PSQI? 

Subjective bias, recall errors, poor accuracy for sleep latency and night awakenings, cultural differences in sleep perception. 

What did Helles et al find about PSQI during lockdown?

Model performs poorly, fit indices were weak, assumption that all components reflect a single construct does not hold in this context. 2-factor model is best; process captures sleep as 2 distinct processes: sleep efficiency and sleep latency. 3-factor model is worse than expected: better than 1 factors, worse than 2 factor, adds complexity without improving explanatory power. 

What are the implications for the PSQI? 

Global PSQI is fragile, treating it as single number is conceptually and statistically weak, especially in non-standard contexts. Structure depends on context. PSQI is under-specified – ignores sleep regularity, chronotype, social jetlag, doesn’t capture environmental stressors, blends behavioural and perceptual variables. 

What does good sleep quality produce? 

Sharper concentration, better decision making, improved memory, ability to manage stress, better immune system, improved physical health, increased energy.

What is insomnia? 

Disorder characterised by persistent difficulty initiating or maintaining sleep despite adequate opportunity accompanied by daytime impairment (fatigue, poor concentration). Not just poor sleep but inability to sleep when conditions are appropriate, often derived by cognitive or physiological hyperarousal. 

What is circadian disruption?

Misalignment between internal biological clock and external environment or schedule, governed by the circadian rhythm. Sleep may be normal in duration or quality but occurs at wrong time, leading to functional impairment (e.g delayed sleep phase, shift work disorder) 

What do behavioural sleep problems arise from?

Habits and environmental factors that interfere with sleep, rather than intrinsic physiological dysfunction. Ex: irregular sleep schedules, excessive schedules, excessive screen use before bed, caffeine intake or poor sleep environments. Meaning sleep could improve if behaviours change.

 

What is perceptual distortion? 

Mismatch between perceived and actual sleep, where individuals systematically misestimate their sleep quantity and quality. Ex: someone may report barely sleeping despite objective evidence of adequate sleep. Common in insomnia and highlights that subjective measures capture belief not ground truth. 

What is actigraphy? 

Method of monitoring sleep-wake patterns using a wrist-worn device that tracks movements over time. Infers whether someone is asleep or awake based on activity levels, typically across days to weeks in real-world settings. 

What is social jet lag? 

Mismatch between your internal biological clock and your social schedule. 

What is chronotype? 

Your body's natural, genetically influenced preference for when you go to sleep and wake up. 

How does sleep effect productivity? 

Energy levels are at their highest in the mid-morning and early afternoon. Often experience a post-lunch dip in energy between 2-4pm. Ideal schedule is aligned with a traditional 9-5 workday.

What is the early bird chronotype? 

Accounts for 15% of population. Sleep pattern is wake early, before dawn and goes to bed early around 9-10pm. Most productive in morning and experiences declining energy levels in afternoon and evening. Best and tackling difficult tasks in the morning and winding down by late afternoon.

What is night owl chronotype? 

About 15% population. Prefers staying up late, often past midnight, and waking up later in the morning or early afternoon. Experiences initial energy burst in afternoon and second, more powerful peak in late evening. Thrive in careers with flexible or late hours, which allows them to work during their peak productivity times. 

What is the Epworth sleepiness scale? 

Widely used in field of sleep medicine as a subjective measure of a patient’s sleepiness 

What is the insomnia severity index? 

Brief self-report questionnaire used to assess the nature, severity, and impact of insomnia symptoms over the past 2 weeks 

What is STOPBANG? 

Screening for obstructive sleep apnoea (OSA). Stands for: Snoring, tiredness/daytime sleepiness, observed apneas, high blood pressure, DM1 > 35 kg/m2, age > 50yrs, neck circumference > 40cm (~ 16 inches), gender: male.