CPAP or Placebo-effect?

In this issue of SLEEP, Kushida and colleagues1 report neurocognitive performance results from a large, multi-site, double blind, controlled, randomized clinical trial on the effects of long-term continuous positive airway pressure (CPAP) therapy.1–3 In this trial, 1,098 patients with obstructive sleep apnea were randomized to active CPAP or sham CPAP (SHAM), with follow-up neurocognitive measures at 2 and 6 months.1–3 Their major findings were: (1) At 2 months, CPAP patients had a significantly better scores than SHAM patients on the sustained working memory test (SWMT), a measure of pre-frontal cortex executive function; being most pronounced for patients with severe OSA. There were no significant differences between groups in other types of cognitive tests. (2) There was a significant association between oxygen saturation and SWMT at 2 months. (3) There was a significant decline in SWMT from 2 to 6 months in the SHAM group but not in the CPAP group. (4) At 6 months, there were no significant differences between groups in SWMT or other measures of CF. (5) Patients on CPAP were significantly less sleepy, as measured by the Epworth Sleepiness Scale (ESS) than patients on SHAM at 2 and 6 months.1 In addition, at baseline, the serial addition test, a simple measure of sustained working memory, was one of a few measures associated with apnea/low oxygen.1,3 The SWMT could not be used at baseline, as it measures change over time