Using polysomnographic data to investigate symptom clusters associated with cognitive decline in patients with obstructive sleep apnea

Cognitive decline (CD) is common in Obstructive Sleep Apnea (OSA) cohorts. Once CD has occurred it may be permanent. If patients at risk for developing CD are detected prior to the onset of symptoms, positive interventions can modify risk factors for CD to prevent or delay its onset. We propose a symptom clustering approach to identify an "At Risk Group" (ARG) with modifiable risk factors for CD. We hypothesized that the levels of individual risk factors in the ARG would indicate increased risk for CD. We used the Psychomotor Vigilance task (PVT) as a measure of established CD and in particular the 10% Slowest Reaction Time (10% SRT). We gathered information from 89 patients having Type 1 diagnostic polysomnography in a hospital sleep laboratory. We defined clusters of ascending severity for excessive daytime sleepiness (EDS), overnight (evening to morning) change of systolic blood pressure (CSBP) and sleep fragmentation (SF), and combined the most severe cluster from each symptom to form an ARG. We obtained PVT parameters from 42 subjects with good and poor results. We compared the levels of EDS, CSBP and SF in the ARG, the best and worst 10% SRT groups and the poor PVT group. The ARG had a CSBP of 9.9±14.8 mmHg and EDS of 12.5±6.4 on the Epworth Sleepiness Scale, in line with reported levels for risk for CD. The severe EDS and the combined severe EDS+CSBP clusters were present at statistically significant levels in the severe 10% SRT group. The ARG may be a viable screening method for patients with OSA at risk for CD.