Working memory in obstructive sleep apnea: construct validity and treatment effects.

STUDY OBJECTIVE To better understand the effects of obstructive sleep apnea (OSA) on working memory performance. We first examined the construct validity of a working memory task (the 2-Back task) and its relationship to other tests of cognitive functioning, and then determined the effects of positive airway pressure (PAP) treatment on measures of both working memory and its related component processes. METHODS Fifty-six participants with OSA were administered cognitive tests of working memory and related subordinate cognitive processes prior to initiation of PAP treatment and at a 3-month follow-up visit. Objective monitors were employed to measure PAP treatment adherence. Statistical analyses were conducted to examine treatment adherence and cognitive performance over time. RESULTS Performance on the 2-Back task was statistically correlated with both a second working memory task (PASAT) and all subordinate cognitive measures. Participants were separated into high and low PAP adherence groups using a median split of 4 hours of PAP use per night. Repeated measures ANOVAs demonstrated that high adherers performed better across time on both tests of working memory (2-Back: F46 = 4.73, p <0.04; PASAT: F46 = 4.92, p <0.04) whereas low adherers performed more poorly. There were no treatment effects for any other cognitive measure. CONCLUSIONS The 2-Back task demonstrated adequate construct validity as a measurement of working memory in individuals with OSA. Our treatment adherence findings suggest that the construct of working memory is more sensitive to the effects OSA treatment than are any of its subordinate cognitive processes.