What polysomnography (PSG) findings are most consistent with normal aging?

Polysomnographic Findings Most Consistent with Normal Aging

The most consistent polysomnographic findings in normal aging include decreased slow-wave sleep (NREM stage 3), increased stage 1 sleep, increased wakefulness after sleep onset, and decreased REM sleep, with relatively preserved stage 2 sleep. 1

Key Sleep Architecture Changes with Normal Aging

Sleep Stage Changes

• Decreased slow-wave sleep (NREM stage 3)

  • Significant reduction in deep sleep, which is most pronounced in the frontal EEG derivations 2
  • For every 10-point decrease in N3% (slow-wave sleep), there is an associated increase in white matter hyperintensities 3

• Increased NREM stage 1 sleep

  • Lighter sleep becomes more prevalent 1, 4
  • Associated with increased sleep fragmentation and arousals

• Preserved NREM stage 2 sleep

  • Relatively stable compared to other sleep stages 1
  • May show modest decreases (around 5%) when using AASM scoring rules 2

• Decreased REM sleep

  • Reduction in total REM sleep time 1, 4
  • REM parameters such as REM density, latency, and number/duration of REM cycles tend to remain stable 1

Sleep Continuity Changes

• Increased wakefulness after sleep onset (WASO)

  • More frequent awakenings during the night 4
  • Reduced sleep efficiency (ratio of time asleep to time in bed)

• Increased sleep stage shifts

  • More transitions between sleep stages, indicating sleep fragmentation 2
  • More than 10 sleep stage shifts per hour are associated with complaints of restless or light sleep 2

Sleep Stability Changes

• Reduced stability of slow-wave sleep

  • Markedly decreased ability to maintain deep sleep 1
  • Sleep structure stability decreases significantly between late 50s and early 70s 1

• Increased arousals

  • More frequent brief awakenings that may not be perceived by the sleeper 4
  • Contributes to sleep fragmentation and complaints of non-restorative sleep

Important Clinical Considerations

Distinguishing Normal Aging from Pathology

• While decreased slow-wave sleep and increased stage 1 sleep are normal with aging, excessive fragmentation may indicate underlying sleep disorders like sleep apnea or periodic limb movement disorder 4

• The American Academy of Sleep Medicine notes that even healthy individuals experience oxygen desaturations during sleep, with mean minimum SpO2 nadirs of 90.4% (±3.1%) in normal subjects 5

Common Pitfalls in Interpretation

• Avoid misattributing pathological findings to normal aging

  • Severe reductions in slow-wave sleep combined with significant oxygen desaturations are more likely indicative of obstructive sleep apnea rather than normal aging 5

• Consider scoring methodology differences

  • AASM scoring rules may result in different percentages of sleep stages compared to Rechtschaffen and Kales criteria, particularly with increased NREM 1 and decreased NREM 2 percentages 2

• Night-to-night variability

  • Single-night studies may not capture the full picture of an individual's sleep patterns 5
  • Consider this variability when interpreting borderline findings

By understanding these normal age-related changes in sleep architecture, clinicians can better distinguish between expected findings and those that warrant further investigation for sleep disorders.