Periodic limb movements do not predict CPAP adherence: The role of sleep fragmentation and disease severity

Periodic limb movements during sleep (PLMS) are common in patients with obstructive sleep apnea (OSA), yet their impact on continuous positive airway pressure (CPAP) adherence remains unclear. This study evaluated whether elevated periodic limb movement index (PLMI) influences CPAP compliance and sleep architecture in OSA patients.

We retrospectively analyzed polysomnographic and CPAP adherence data from 150 adults diagnosed with OSA. Participants were stratified into two groups: PLMI ≥15 (elevated) and PLMI <15 (normal). CPAP compliance was assessed by percentage of days CPAP was used, percentage of days with ≥4 h of use, and mean nightly hours of use. Regression analyses adjusted for age, sex, apnea-hypopnea index (AHI), and arousal index.

Patients with elevated PLMI ≥15: n = 72; PLMI <15: n = 78. Had a higher arousal index compared with those with normal PLMI (20.6 ± 26.2 vs. 10.2 ± 10.3; p = 0.01). They also spent less time in N3 sleep (6.6 % ± 6.9 % vs. 9.6 % ± 7.3 %; p = 0.004) and REM sleep (8.9 % ± 7.3 % vs. 12.3 % ± 8.3 %; p = 0.01). CPAP adherence did not differ significantly between groups. In adjusted models, male sex predicted greater CPAP use (β = 6.55, p = 0.03), while a higher arousal index was associated with shorter nightly use (β = -0.06, p = 0.03). AHI predicted longer nightly CPAP use (β = 0.05, p < 0.001).

Elevated PLMI is associated with greater sleep fragmentation and reduced slow-wave and REM sleep, but does not independently predict CPAP non-adherence. Instead, sex, AHI, and arousal index are stronger determinants of CPAP usage. These findings highlight the importance of addressing both OSA severity and sleep continuity when evaluating CPAP outcomes.