EEG Sleep Spectra in Older Adults Across All Circadian Phases During NREM Sleep

Mar 27, 2010Sleep

Brain activity during deep sleep across all daily rhythms in older adults

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Abstract

EEG activity in slow wave, theta, alpha, and high spindle ranges was significantly greater during forced desynchrony than baseline nights.

Sleep scheduled at various times led to increased EEG activity across multiple frequency ranges, indicating altered sleep patterns.
EEG delta activity was higher in the biological morning and early afternoon compared to other times, suggesting a significant interaction between homeostatic and circadian factors.
Overall EEG activity showed significant increases during the biological day compared to the biological night, except in the lower EEG spindle range.
EEG beta activity was positively correlated with wakefulness and negatively correlated with total sleep time, highlighting potential challenges in sleep consolidation.

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STUDY OBJECTIVES: Healthy aging is associated with changes in sleep-wake regulation, and those changes often lead to problems sleeping, both during the night and during daytime. We aimed to examine the electroencephalographic (EEG) sleep spectra during non-rapid eye movement (NREM) sleep when sleep was scheduled at all times of day.

DESIGN/INTERVENTIONS: After three 24-h baseline (BL) days, participants were scheduled to live on 20-hour "days" consisting of 6.7 hours of bed rest and 13.3 hours of wakefulness for 12 consecutive days (forced desynchrony, FD). The EEG was recorded from a central derivation during all scheduled sleep episodes, with subsequent visual scoring and spectral analysis.

SETTING: Intensive Physiological Monitoring Unit of the Brigham & Women's Hospital General Clinical Research Center.

PARTICIPANTS: Twenty-four healthy older subjects (64.2 +/- 6.3 yr; 13 women, 11 men)

MEASUREMENTS AND RESULTS: Compared with BL nights, EEG activity in the slow wave (0.5 to 5.25 Hz), theta (6 to 6.25 and 7 Hz), alpha (10 to 11.25 Hz), and high spindle range (14.5 to 15.5 Hz) was significantly greater during FD, when subjects slept across many times of day and night. During FD, there was a significant interaction between homeostatic and circadian factors, such that EEG delta activity (0.5 to 1.5 Hz) was higher in the biological morning/early afternoon than at other times. EEG activity was significantly increased in almost all frequency ranges (0.5 to 21 Hz) during the biological day, as compared with the biological night, except for the lower EEG spindle range (12.25 to 14 Hz). Overall, EEG beta activity was positively correlated with wakefulness and negatively correlated with total sleep time.

CONCLUSION: Our findings provide some new evidence for the underlying mechanisms that contribute to age-related difficulties in sleep consolidation, especially when sleep occurs during the daytime.

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EEG Sleep Spectra in Older Adults Across All Circadian Phases During NREM Sleep

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