Characteristics and Determinants of Respiratory Event-Associated Leg Movements

To (1) replicate the recently described distribution of respiratory event-associated leg movements (rLMs) in participants with mild-to-moderate obstructive sleep apnea syndrome (OSAS), (2) explore global and local factors associated with the presence of rLMs, and (3) investigate differences related to OSAS severity and periodic leg movements during sleep (PLMS) status.

We randomly selected six groups of participants without restless legs syndrome (12-15 participants in each group), stratified by apnea-hypopnea index (AHI) severity (AHI 10-20, 20-30, and 30-40) and PLMS status (PLMS index <15 and >15 per hr) from the population-based HypnoLaus study that assessed full polysomnography at home in participants aged 40 to 80 years, randomly selected from the population register of the city of Lausanne, Switzerland.

Our results confirmed the distribution of leg movement activity at the end of respiratory events (-2.0 to +10.25 s). Mixed effects logistic regression modeling rLM-probability showed that rLMs were more frequent in participants with high-PLMS, at the end of obstructive apneas (vs. hypopneas) and in the presence of arousals at the end of the events. In participants with high-PLMS, rLM-probability decreased with time of night and was more reduced during REM sleep (vs. NREM sleep), whereas the duration of the respiratory event had a significant effect only in participants with low-PLMS.

We confirm the previously reported distribution of rLMs in participants with mild-to-moderate OSAS and our results suggest that rLMs are sensitive to both sleep-related and respiratory-related factors in a complex interaction with the PLMS status.