Our aim was to evaluate the circadian rhythm of distal skin temperature (DST) in Sleep Disordered Breathing (SDB), its relation to excessive daytime sleepiness and the effect of continuous positive airway pressure (CPAP) on DST.
Eighty SDB patients (53.1±1.2 years old, 27.6% women) and 67 healthy subjects (52.3±1.6 years old, 26.9% women) wore a temperature data logger for one week. On the last day of that week, SDB patients underwent a polysomnography followed by a Maintenance of Wakefulness Test (MWT), Multiple Sleep Latency Test (MSLT) and Sustained Attention to Response Task (SART) protocol to objectively quantify daytime sleepiness. A subset of 21 moderate to severe SDB patients was treated with CPAP during at least 3 months and revaluated with the same procedure. A non-parametrical analysis was performed to characterize DST to assess differences between groups and associations among DST, polysomnography and daytime sleepiness measures.
SDB patients showed an unstable, fragmented, flattened, phase-advanced and less robust DST rhythm as compared to healthy subjects. Besides, the more severe the SDB, the worse the DST pattern was, as indicated by the correlation coefficient. Sleepiness, according to MWT sleep latencies, was also associated with the higher fragmentation, lower amplitude and less robustness of the DST rhythm. Treatment with CPAP improved DST pattern regularity and robustness.
DST is altered in SDB, exhibiting a direct relationship to the severity of this condition, while improves with CPAP treatment. DST independently correlates with sleepiness, thus, its measurement may contribute to the understanding of the pathophysiology of sleepiness in these patients.