Increased Flow Limitation During Sleep Is Associated With Increased Psychomotor Vigilance Task Lapses in Individuals With Suspected OSA

Abstract

BackgroundImpaired daytime vigilance is an important consequence of obstructive sleep apnea (OSA), but several studies have reported no association between objective measurements of vigilance and the apnea-hypopnea index (AHI). Notably, the AHI does not quantify the degree of flow limitation, i.e., the extent to which ventilation fails to meet intended ventilatory drive. Research QuestionIs flow limitation during sleep associated with daytime vigilance in OSA? Study Design and Methods998 participants with suspected OSA completed a 10-minute psychomotor vigilance task (PVT) prior to same-night in-laboratory polysomnography. Flow limitation frequency (percent of flow-limited breaths) during sleep was quantified using airflow shapes (e.g., fluttering and scooping) from nasal pressure airflow. Multivariable regression assessed the association between flow limitation frequency and the number of lapses (response times > 500 ms, primary outcome), adjusting for age, sex, body mass index, total sleep time, depression, and smoking status. ResultsIncreased flow limitation frequency was associated with decreased vigilance: one standard deviation (35.3%) increase was associated with 2.1 additional PVT lapses (95% CI 0.7−3.7, P = 0.003). This magnitude was similar to that for age, where one standard deviation increase (13.5 years) was associated with 1.9 additional lapses. Results were similar after adjusting for AHI, hypoxemia severity, and arousal severity. The AHI was not associated with PVT lapses (P = 0.20). In secondary exploratory analysis, flow limitation frequency was associated with mean response speed (P = 0.012), median response time (P = 0.029), fastest 10% response time (P = 0.041), slowest 10% response time (P = 0.018), and slowest 10% response speed (P = 0.005). InterpretationIncreased flow limitation during sleep was associated with decreased daytime vigilance in individuals with suspected OSA, independent of AHI. Flow limitation may complement standard clinical metrics in identifying individuals whose vigilance impairment is most likely explained by their OSA.