What causes decreased sleep efficiency on a sleep study in a laboratory setting?

Causes of Decreased Sleep Efficiency in Laboratory-Based Sleep Studies

Decreased sleep efficiency in laboratory-based sleep studies is primarily caused by the "first night effect," environmental factors in the sleep laboratory, and underlying sleep disorders, particularly insomnia, obstructive sleep apnea, and restless leg syndrome. 1, 2

First Night Effect and Environmental Factors

• First night effect: The unfamiliar and restrictive environment of the sleep laboratory leads to artificially reduced sleep efficiency, especially pronounced in patients with insomnia 1

  • Can take up to four polysomnographic studies to resolve completely 1
  • Results in increased sleep latency and decreased total sleep time

• Environmental disruptions:

  • Unfamiliar bed and surroundings
  • Monitoring equipment (sensors, wires, etc.)
  • Ambient noise from equipment and staff
  • Different lighting conditions than home environment
  • Room temperature differences 3

Sleep Disorders Contributing to Decreased Efficiency

Primary Sleep Disorders

• Insomnia: Characterized by difficulty falling asleep, maintaining sleep, and early morning awakening 1

  • Patients with insomnia show significant misperception between subjective and objective sleep measures 4
  • Median discrepancy of 46 minutes in total sleep time and 11% in sleep efficiency 4

• Obstructive Sleep Apnea (OSA):

  • Severe OSA associated with 2.16 times higher odds of poor sleep efficiency 2
  • Frequent arousals and awakenings due to respiratory events 1

• Restless Leg Syndrome (RLS) and Periodic Limb Movement Disorder:

  • Up to 45% of older adults have periodic limb movements during sleep 1
  • Movements cause brief or prolonged awakenings 1

Age-Related Factors

• Older age: Associated with 48% higher odds of poor sleep efficiency per 10-year increase 2
• Age-related changes in sleep architecture:
  • Decreased slow wave and REM sleep
  • Increased stages 1 and 2 sleep
  • Frequent interruptions of sleep by long periods of wakefulness 1

Medical and Psychiatric Comorbidities

• Medical conditions:

  • Chronic pain conditions
  • Cardiovascular disease
  • Respiratory disorders
  • Neurological conditions 5
  • Atopic dermatitis (causes nocturnal itching and scratching) 1

• Psychiatric conditions:

  • Depression and anxiety significantly impact sleep efficiency 6
  • Contribute 8-9% of the variance in subjective sleep quality 6

Biochemical and Physiological Factors

• Laboratory abnormalities:

  • Elevated phosphate and urea levels correlate with impaired sleep efficiency 7
  • Hemoglobin levels outside the 10-12 g/dl range associated with worse sleep efficiency 7

• Medications:

  • CNS stimulants
  • Some antidepressants
  • Beta-blockers
  • Corticosteroids 1

Clinical Implications

• Sleep efficiency in laboratory settings is typically lower than home settings but remains clinically relevant 2
• Poor sleep efficiency (≤50%) affects approximately 8% of patients undergoing laboratory polysomnography 2
• Male sex is associated with 34% higher odds of poor sleep efficiency 2

Recommendations for Improving Sleep Study Accuracy

• Consider using actigraphy for extended data collection prior to laboratory sleep studies 1
• When possible, conduct multiple night studies to account for first night effect 1
• Document and consider the patient's regular sleep habits and environment 3
• Optimize laboratory conditions to minimize environmental disruptions 3

Sleep efficiency remains an important metric in sleep studies despite these limitations, as it provides valuable information about sleep quality and potential sleep disorders that impact morbidity, mortality, and quality of life.