Sleep Studies and CPAP Administration

Sleep studies took place either through normal clinical channels for those recruited from sleep clinics (level 1 polysomnography or level 3 home sleep tests), or administered by the investigators for those recruited from cardiology or diabetes clinics (using either Embletta Gold or Embletta X100, Embla). All studies were scored by a single registered polysomnographic technologist using the American Academy of Sleep Medicine (AASM) alternative hypopnea criteria when arousal data were available, or the AASM-recommended criteria when electroencephalographic data were not recorded.¹⁵

Participants were instructed on the use of CPAP during a 1-hour appointment with a sleep technologist, which followed a written manual of procedures and a standardized checklist. Unless an in-laboratory CPAP titration had been performed, participants used an autoadjusting device for a minimum of 5 days with the 90th or 95th percentile pressure used for ongoing fixed CPAP depending on the device manufacturer (Philips Respironics and ResMed devices report the 90th and 95th percentile pressures, respectively). CPAP devices used were the REMStar Auto (Philips Respironics) or the S9 Autoset (ResMed).

The original trial design included follow-up for 12 months; however, subjects randomly assigned after January 2013 were restricted to 6 months of follow-up.¹³ Our primary analysis of CPAP adherence therefore took place for 6 months, rather than 12. During follow-up, all participants were offered 30-minute appointments with a sleep technologist 1 week, 1 month, 3 months, 6 months, and (where applicable) 9 months after randomization, focused on OSA and CPAP education and technical troubleshooting.

Subjects randomly assigned to the CPAP-only arm underwent sleep studies and CPAP administration as described. Those randomly assigned to CPAP + ME underwent the intervention in addition to the procedures performed in the CPAP-only arm.