Large muscle group movements during sleep in healthy people: normative values and correlation to sleep features

STUDY OBJECTIVES: To investigate the frequency and characteristics of large muscle group movements (LMMs) during sleep in healthy adults. METHODS: LMMs were scored following the International Restless Legs Syndrome Study Group criteria in 100 healthy participants aged 19–77 years. A LMM was defined as a temporally overlapping increase in EMG activity and/or the occurrence of movement artifacts in at least two channels. LMM indices and durations in total sleep time (TST), NREM and REM sleep, and association with arousals, awakenings, and/or respiratory events were calculated. Correlations of LMMs indices and durations with sleep architecture, respiratory and motor events, and subjective sleep quality were investigated. RESULTS: Median LMMs index in TST was 6.8/h (interquartile range (IQR), 4.5–10.8/h), median mean duration 12.4 s (IQR 10.7–14.4 s). Mean LMMs duration was longer in NREM (median 12.7 s, IQR 11.1–15.2 s) versus REM sleep (median 10.3 s, IQR 8.0–13.5s), p < 0.001. LMMs associated with awakening increased with age (p = 0.029). LMMs indices in TST were higher in men than women (p = 0.018). LMMs indices correlated positively with N1 sleep percentage (ρ = 0.49, p < 0.001), arousal index (ρ = 0.40, p = 0.002), sleep stages shift index (ρ = 0.43, p < 0.001, apnea index (ρ = 0.36, p = 0.017), and video-visible movements indices (ρ = 0.45, p < 0.001), and negatively with N3 sleep (ρ = −0.38, p= 0.004) percentage. CONCLUSIONS: This is the first study providing normative data on LMMs frequency in healthy adults. LMMs are a ubiquitous phenomenon often associated with other events. Correlation with arousals and respiratory events suggests a potential clinical significance of LMMs in adults that awaits further investigation.