Cyclic alternating pattern and sleep quality in healthy subjects--is there a first-night effect on different approaches of sleep quality?

Objective: Cyclic alternating pattern (CAP) is defined as periodic EEG activity during NREM sleep that reflects unstable sleep and represents a marker of instability of the sleep process. The aim of the present investigation was to analyze sleep quality of 28 healthy subjects (mean age 53.3+/-21.3 years) over two consecutive nights and determine potential differences between them ("first-night effect").

Methods: Evaluations comprised objective and subjective sleep variables as well as macrostructural and microstructural variables of sleep.

Results: Macrostructural analysis showed significant differences between the first and the second sleep laboratory night in REM latency (122.39+/-60.46 min vs. 95.43+/-36.60 min; T=3.431; p=0.002) and the amount of sleep stage 1 (42.60+/-21.80 min vs. 39.70+/-18.95 min; T=2.223; p=0.035). Microstructural analysis revealed a significant decrease in the CAP rate (1st night: 33.29%; 2nd night: 26.34%; T=3.288; p=0.003) and in the amount of subtype A2 (74.79+/-43.47 vs. 58.50+/-23.22; T=2.185; p=0.038). Subjective variables also demonstrated a significant increase of drive (T=2.564; p=0.016).

Conclusion: Healthy subjects show hardly any macrostructural differences between the first and the second night in the sleep laboratory. On the microstructural level differences in CAP variables were found.

Significance: Microstructural analysis can be seen as a further approach to the classification of sleep and CAP turned out to be sensitive to environmental influences on sleep.