Cardiovascular Mortality in Obstructive Sleep Apnea in the Elderly: Role of Long-Term Continuous Positive Airway Pressure Treatment. A Prospective Observational Study
What is the impact of obstructive sleep apnea (OSA) and continuous positive airway pressure (CPAP) treatment on cardiovascular mortality in men and women over 65 years, who were referred to sleep units for suspected OSA?
This was a prospective observational study of a consecutive cohort of elderly patients (>65 years old) studied for suspicion of OSA between 1998 and 2007. Subjects were excluded if they had previous treatment with CPAP, unwillingness to undergo a sleep study, and the presence of a central sleep apnea syndrome (>50% of apneic events). Participants were divided into four groups. Patients with an apnea-hypopnea index (AHI) of <15 were the control group. OSA was defined as mild to moderate (AHI, 15-29) or severe (AHI, >30). Patients with OSA were classified as CPAP-treated (adherence ≥4 h/d) or untreated (adherence but <4 h/d or not prescribed). Participants were monitored until December 2009. The endpoint was cardiovascular death, defined as death from stroke, heart failure, or myocardial infarction. A multivariate Cox survival analysis was used to determine the independent impact of OSA and CPAP treatment on cardiovascular mortality.
Screening of 1,005 elderly patients with suspected OSA was done in two centers. After removing exclusions and losses to follow-up, 939 were followed for a median follow-up of 69 months. A total of 601 (64%) men were included in this study (mean age 71.2 years). Four groups were established: control group (n = 155), mild to moderate OSA without CPAP therapy (n = 108), severe OSA without CPAP therapy (n = 173), and OSA with CPAP therapy (n = 503). Significant differences were observed in the OSA groups in body mass index and previous cardiovascular events (stroke, heart failure, arrhythmias, and ischemic heart disease), but no statistical difference among OSA groups and control subjects with smoking history, diabetes, hyperlipidemia, or hypertension. During study follow-up, 190 deaths occurred (20.2%); more than one-half were of cardiovascular in origin. Causes of death were confirmed by hospital medical records or by official death certificates. Compared with the control group, the fully adjusted hazard ratios for cardiovascular mortality were 2.25 (confidence interval [CI], 1.41-3.61) for the untreated severe OSA group, 0.93 (CI, 0.46-1.89) for the CPAP-treated group, and 1.38 (CI, 0.73-2.64) for the untreated mild to moderate OSA group. These results were not driven by death from ischemic heart disease. CPAP treatment was associated with a reduced risk of death from stroke and heart failure to levels similar to those without OSA or those with untreated mild OSA. However, there were no changes in the risk of death due to ischemic heart disease.
The authors concluded that severe OSA not treated with CPAP is associated with cardiovascular death in the elderly, and adequate CPAP treatment may reduce this risk.
The excess in mortality here seems to be from cerebrovascular and heart failure causes, and CPAP treatment is associated with a decrease in the risk of mortality to levels similar to those found in patients without OSA. Although additional research is required, this study is an important step in developing evidence for this common, but relatively understudied disorder in the elderly.
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