ATLANTA–A study of veterans who were prescribed Continuous Positive Airway Pressure (CPAP) therapy after having a stroke or transient ischemic attack (TIA)found that their compliance with the treatment had a significant association with how regularly they also took cardiovascular medications.
“Given the benefits of these medications on cardiovascular morbidity and mortality, not controlling for this correlation may contribute to a healthy user bias in the interpretation of observational CPAP trials,” suggest the researchers from Yale University. The study was presented recently at the annual CHEST conference.
A common criticism of studies on CPAP use is the potential for bias from the “healthy user effect,” which suggests that CPAP users may be more compliant with medical co-therapies, leading to improved outcomes. To determine the potential for that effect, investigators analyzed the concurrent usage of CPAP and medications.
Study subjects were part of the VA’s “Go To Sleep” study, which included hypertensive veterans with a history of stroke or TIA who lacked a previous diagnosis of sleep apnea. Selection criteria included new diagnosis of sleep apnea, having a home CPAP device, and receiving lipid-lowering, anti-hypertensive, or non-aspirin anti-platelet agents from the VA pharmacy.
Data directly downloaded from the CPAP device provided information on the machines’ usage. Medication usage was determined by tracking pharmacy medication refills.
Of 46 total patients, 35% met criteria for CPAP compliance, defined as more than four hours of usage per nights more than 70% of the time.
Researchers found that CPAP compliance was significantly associated with adequate combined cardiovascular medication adherence (p=0.016), with a 1.7-fold relative risk (95%CI [1.2,2.3]) for CPAP compliance given medication adherence, and a 6.6-fold relative risk for medication adherence given CPAP compliance [0.95,45]. An especially significant association was found between adequate adherence to lipid-lowering therapy and CPAP compliance.
1. Dieffenbach P, Bravata D, Ferguson J, et. al “Investigating the Healthy User Effect: Correlating CPAP Use and Medication Adherence.” CHEST. October 2012;142(4_MeetingAbstracts):1053A-1053A. doi:10.1378/chest.1386770