Long-Term Effects of Nasal Continuous Positive Airway Pressure Therapy on Cardiovascular Outcomes in Sleep Apnea Syndrome

Liam S. Doherty, MD; John L. Kiely, MD; Valerie Swan, RgN; Walter T. McNicholas, MD, FCCP

Disclosures

CHEST. 2005;127(6):2076-2084. 

In This Article

Abstract and Introduction

Background: Obstructive sleep apnea syndrome (OSAS) has been associated with increased morbidity and mortality, principally from cardiovascular disease, but the impact of nasal continuous positive airway pressure (CPAP) therapy is unclear.
Methods: We performed a long-term follow-up study of 168 patients with OSAS who had begun receiving CPAP therapy at least 5 years previously, most of whom had been prospectively followed up, having been the subject of an earlier report on cardiovascular risk factors in OSAS patients. The average follow-up period was 7.5 years. We compared the cardiovascular outcomes of those patients who were intolerant of CPAP (untreated group, 61 patients) with those continuing CPAP therapy (107 patients).
Results: CPAP-treated patients had a higher median apnea-hypopnea index score than the untreated group (48.3 [interquartile range (IQR), 33.6 to 66.4] vs 36.7 [IQR, 27.4 to 55], respectively; p = 0.02), but age, body mass index, and time since diagnosis were similar. Deaths from cardiovascular disease were more common in the untreated group than in the CPAP-treated group during follow-up (14.8% vs 1.9%, respectively; p = 0.009 [log rank test]), but no significant differences were found in the development of new cases of hypertension, cardiac disorder, or stroke. Total cardiovascular events ( ie , death and new cardiovascular disease combined) were more common in the untreated group than in the CPAP-treated group (31% vs 18%, respectively; p < 0.05).
Conclusions: The data support a protective effect of CPAP therapy against death from cardiovascular disease in patients with OSAS.

Obstructive sleep apnea syndrome (OSAS) has a prevalence of 2 to 4% in the adult population[1] and is associated with a reduced quality of life[2] and increased risk of road traffic accidents due to excessive sleepiness.[3] Continuous positive airway pressure (CPAP) is an effective therapy and is the most widely used modality in patients with moderate-to-severe disease.[4] OSAS is also associated with an increased risk of cardiovascular disease,[5,6,7,8,9] especially hypertension.[10,11,12] However, the evidence that OSAS is an independent risk factor for cardiovascular disease or death has been disputed[13] on the basis that some previous studies[14,15,16] supporting a causative association may have been too small, may have failed to take into account other known cardiovascular risk factors, or may have had an inadequate duration of follow-up. Furthermore, Veale and coworkers[17] found that, although the overall mortality rate was similar to that of the normal population, patients with OSAS who had been prescribed nasal CPAP therapy died mainly from cardiovascular disease.

If OSAS is an independent risk factor for the development of cardiovascular disease, it could be hypothesized that effective therapy for the disorder would likely reduce the long-term risk of the development and progression of such disease, and two reports[18,19] have supported this possibility. We have previously reported[20] the cardiovascular risk factors of 114 consecutive patients with OSAS who were assessed in our unit. Using this prospective patient cohort, together with other patients in whom OSAS had previously been diagnosed, for whom similar baseline data as those in this report were available, we performed a long-term follow-up study comparing the cardiovascular outcomes of those patients who continued to receive CPAP therapy with those who had quit therapy. The primary outcome of the study was cardiovascular morbidity and mortality, and this outcome was designated prior to the study.

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