Effect of obstructive sleep apnoea treatment on sleep spindles: a systematic review and meta-analysis

The consequences of untreated obstructive sleep apnea (OSA) on health are well established. OSA alterations to sleep microarchitecture include a reduction in sleep spindles during NREM sleep, a neurophysiological biomarker that reflects sleep stability, cognitive function and brain health. However, the effects of OSA treatment on reversing sleep spindle abnormalities remains unclear. This systematic review evaluated the effect of continuous positive airway pressure (CPAP) treatment on spindles during polysomnography in adults diagnosed with OSA. We identified five papers meeting inclusion criteria with a total of 202 participants. Two studies analyzed spindle density after 6 months of CPAP use and three analyzed spindle activity during CPAP titration. Three studies used automatic spindle detection methods. Meta-analysis showed a significant increase in spindle density after CPAP use (mean difference = 1.16 spindles/min, 95 % CI [0.27, 2.04], p = 0.010). However, heterogeneity was high due to variability in study designs, sample sizes, and methodological factors. In conclusion, CPAP treatment increased spindle density in adult patients with OSA. Future research should aim to standardize spindle detection protocols and incorporate both objective and subjective measures. Establishing whether spindle changes mediate the functional recovery seen with CPAP will be essential to investigate their potential clinical utility.