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Investigating the Healthy User Effect: Correlating CPAP Use and Medication Adherence FREE TO VIEW

Paul Dieffenbach*, MD; Dawn Bravata, MD; Jared Ferguson, BS; Vincent McClain, MD; Charles Austin, MA; Frederick Struve, PhD; Xinli Li, PhD; Linda Williams, MD; Jason Sico, MD; Carlos Fragoso, MD; Nicholas Burrus, BA; John Concato, MD; Nancy Kim, MD; H. Klar Yaggi, MD
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Department of Internal Medicine, Yale University School of Medicine, New Haven, CT

Chest. 2012;142(4_MeetingAbstracts):1053A. doi:10.1378/chest.1386770
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PRESENTED ON: Monday, October 22, 2012 at 04:00 PM - 05:30 PM

PURPOSE: Observational data support the use of Continuous Positive Airway Pressure (CPAP) therapy to reduce cardiovascular morbidity and mortality in patients with obstructive sleep apnea. One common critique of these findings is the potential for bias from the “healthy user effect,” which postulates that CPAP users may be more compliant with medical co-therapies that predispose them to improved outcomes. To examine the potential for this effect, we performed an analysis of contemporaneous CPAP and cardiovascular medication usage in patients after stroke or transient ischemic attack (TIA).

METHODS: Subjects were taken from the GoToSleep study, which comprised hypertensive veterans with a history of stroke or TIA who lacked a previous diagnosis of sleep apnea. GoToSleep patients were eligible for the current project if they were newly diagnosed with sleep apnea, obtained a home CPAP device, and received lipid-lowering, anti-hypertensive, or non-aspirin anti-platelet agents from the VA pharmacy. CPAP compliance was assessed using data directly downloaded from the CPAP machines. Medication usage was assessed by tracking pharmacy medication refills, with 80% coverage by a given drug class as a threshold for adequate adherence.

RESULTS: Of 46 total patients, 35% met criteria for CPAP compliance (> four hours use per night for >70% of nights). 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]. Analysis of individual drug classes revealed a significant association between adequate adherence to lipid-lowering therapy and CPAP compliance (p=0.02).

CONCLUSIONS: In this study of veterans initiated on CPAP after stroke or TIA, adherence to cardiovascular medications was significantly associated with CPAP compliance over a six month period.

CLINICAL IMPLICATIONS: This analysis reveals a correlation between CPAP compliance and cardiovascular medication adherence. 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.

DISCLOSURE: The following authors have nothing to disclose: Paul Dieffenbach, Dawn Bravata, Jared Ferguson, Vincent McClain, Charles Austin, Frederick Struve, Xinli Li, Linda Williams, Jason Sico, Carlos Fragoso, Nicholas Burrus, John Concato, Nancy Kim, H. Klar Yaggi

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Department of Internal Medicine, Yale University School of Medicine, New Haven, CT




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