Sleep Across the Lifespan Wk2 L1

Lecture Overview

• Speaker: Kath Madison

• Topics Covered:

  • Sleep across the lifespan

  • Sleep in other mammals

• Lecture Outcomes:

  • Outline impact of normal aging on sleep architecture

  • Compare sleep patterns and structure in males and females

  • Contrast sleep behavior in humans vs. other species

Sleep Architecture

• Definition: Basic structural organization of normal sleep.

• Physiological Signals Recorded:

  • Brainwave activity

  • Eye movements

  • Muscle movements

• Hypnogram: Visual representation of sleep cycles.

• Types of Sleep in Adults:

  • Two states: Non-REM (NREM) and REM sleep.

  • Four stages of NREM: Stage 1, Stage 2, Stage 3.

  • REM Sleep: Rapid Eye Movement (Stage R).

Sleep Across the Lifespan

Infants (0-3 months)

• Sleep Types:

  • Quiet Sleep: Similar to NREM

  • Active Sleep: Comparable to REM

• Sleep Patterns:

  • Constant cycling every 20-60 minutes.

  • Frequent wakings normal.

• Sleep Duration: Up to 80% of the day.

  • Equal time between active (50%) and quiet sleep (45%).

Toddlers (3-5 months to 1 year)

• Decrease in REM sleep as age increases, shifting to more NREM.

• Sleep Development:

  • Active sleep decreases to 40% by 3-5 months.

  • By 1 year: 25-30% in REM, similar to adults.

Pattern Changes in Childhood to Adulthood

• Age 1: Begin consolidating sleep with primarily nighttime sleep and two strong nap periods (Polyphasic Sleep).

• Age 4: Shift to one nap and predominantly night sleep (Biphasic Sleep).

• Age 10+: Move to monophasic sleep with consolidated nighttime sleep.

• Changes in Sleep Preference:

  • Teenagers: Later sleep preference (evening chronotype).

  • Elderly: Shift to earlier bedtimes (morning chronotype).

Recommended Sleep Durations Across Ages

• Newborns: 14-17 hours (11-19 hours may be appropriate).

• Infants: 12-15 hours; Toddlers: 11-14 hours; Preschoolers: 10-13 hours.

• School-aged Children: 9-11 hours; Teenagers: 8-10 hours; Young Adults: 7-9 hours (10-11 hours upper limit).

• Adults: 7-9 hours; Older Adults: 7-8 hours.

Impact of Aging on Sleep Architecture

• Key Findings from 2019 Meta-analysis:

  • Decreased total sleep time with age.

  • Increased sleep onset latency.

  • No significant changes in time spent in NREM Stage 2, Stage 3, or REM across age.

  • Increased prevalence of sleep disorders, e.g., obstructive sleep apnea in older adults.

Factors Influencing Sleep Changes in Older Adults

• Circadian rhythm changes: Shift in optimal sleeping times.

• Increased napping prevalence: 25%-80% in older adults.

• Health comorbidities: Impact sleep quality.

  • Common issues: chronic pain, nocturia, and other medical conditions.

• Psychosocial factors: Caregiving, Sedentary lifestyle, Social isolation.

Sleep and Biological Sex/Gender

In Males

• Testosterone: Circulates in a 24-hour rhythm, impacting sleep.

• Increased risk of sleep disorders (especially respiratory) with aging.

In Females

• Hormonal Milestones:

  • Puberty

  • Pregnancy

  • Menopause

• Hormonal Impact:

  • Changes in progesterone and estrogen linked to sleep disturbances.

Gender Differences in Sleep Patterns

• Gender Minority Groups: Increased prevalence of poor sleep health.

  • Higher rates of insomnia in transgender and non-binary individuals.

Sleep in Other Mammals

Terrestrial Mammals

• Variation in total sleep duration and sleep cycle lengths.

• Sleep behaviors: Posture, timing, and environmental adaptation.

Marine Mammals

• Differences in sleep patterns (uni-hemispheric sleep).

• Examples: Dolphins rarely exhibit REM sleep; behavior adapted to aquatic life.

Sleep Theories in Animals

1. Immobilization Theory: Sleep minimizes movement to avoid predation.

2. Information Processing/Growth: Sleep linked to neural development, especially in young.

3. Energy Conservation: Sleep may lower metabolic rate to save energy.

Conclusion

• Sleep variability across lifespan influences health.

• Differences in sleep architecture observed, both intra and inter-species.

• Further research is needed on sleep in gender minority groups and across different mammalian species.