Untreated severe obstructive sleep apnea (OSA) is associated with an increased risk of cardiovascular mortality in the elderly, and adequate treatment with continuous positive airway pressure (CPAP) may significantly reduce this risk, according to a new study from researchers in Spain.

"Although the link between OSA and cardiovascular mortality is well established in younger patients, evidence on this relationship in the elderly has been conflicting," said lead author Miguel Ángel Martínez-García, MD, of La Fe University and Polytechnic Hospital in Valencia, Spain. "In our study of 939 elderly patients, severe OSA not treated with CPAP was associated with an increased risk of cardiovascular mortality especially from stroke and heart failure, and CPAP treatment reduced this excess of cardiovascular mortality to levels similar to those seen in patients without OSA."

The findings were published online ahead of print publication in the American Thoracic Society's American Journal of Respiratory and Critical Care Medicine.

All subjects in this prospective, observational study were 65 years of age or older. Median follow-up was 69 months. Sleep studies were conducted with either full standard polysomnography or respiratory polygraphy following Spanish guidelines. OSA was defined as mild-to-moderate (apnea-hypopnea index [AHI] 15-29) or severe (AHI ≥30). Patients with AHI <15 acted as controls. CPAP use ≥4 hours daily was considered as good adherence to treatment.

Compared with the control group, the adjusted hazard ratios for cardiovascular mortality were 2.25 (CI, 1.41 to 3.61) for patients with untreated severe OSA, 0.93 (CI, 0.46 to 1.89) for patients treated with CPAP and 1.38 (CI, 0.73 to 2.64) for patients with untreated mild-to-moderate OSA. Similar results were observed among the subgroup of patients ≥75 years of age. Among patients who initiated CPAP treatment, compliance was independently associated with a reduced risk of cardiovascular mortality.

The study had a few limitations, including that the study was not randomized, the reduced statistical power in the subgroup analyses, and the use of respiratory polygraphy to diagnose OSA in a number of patients. Strengths included being the large study size including exclusively elderly patients and the long follow-up.

"This is the first large-scale study to examine the impact of OSA on cardiovascular mortality in a series including exclusively elderly patients and assess the effectiveness of CPAP treatment in reducing this risk," said Dr. Martínez-García. "Our finding that adequate CPAP treatment is associated with significant reductions in cardiovascular mortality in patients with OSA has important implications, especially given the increasing elderly population."