SEATTLE — The greater endothelial dysfunction is among patients with obstructive sleep apnea, the more cardiovascular conditions they are likely to develop over time, according to a survey of 86 patients.
“The fact that endothelial dysfunction is predictive of cardiovascular events is well established in the cardiovascular literature,” Dr. Giora Pillar, a sleep medicine specialist with the Technion–Israel Institute of Technology, Haifa, said at the annual meeting of the Associated Professional Sleep Societies. However, this association has not been well studied among patients with obstructive sleep apnea (OSA).
He and his colleagues conducted follow-up telephone interviews with 86 patients with OSA who had undergone assessment of endothelial function with the postobstruction reactive hyperemia test when their OSA was diagnosed. Most (77%) were men and, at diagnosis, the patients had a mean age of 53 years and a mean body mass index of 29.2 kg/m
During the interviews, which took place an average of 4.3 years after the endothelial function assessment, patients were asked about OSA treatment, lifestyle changes, and diagnoses made and medications prescribed by their primary care physicians.
The investigators assessed the new onset of seven cardiovascular-related conditions: hypertension, diabetes, dyslipidemia, angina pectoris, myocardial infarction, stroke, and cardiac arrhythmia. Each condition was assigned one point, and the points were totaled.
“It could be argued whether diabetes and dyslipidemia are cardiovascular complications,” Dr. Pillar acknowledged. But they were included because “recent publications show that if you take lean patients [with OSA], they are at risk to develop obesity and dyslipidemia because of insulin resistance, changes in their lipid profiles, and other factors.”
Results indicated that 13% of the patients who smoked at baseline had stopped smoking at follow-up, and 22% of patients had started exercising, he reported. However, the patients' BMI was unchanged.
“Surprisingly, only 17 patients, which is 20% of our cohort, were treated with continuous positive airway pressure (CPAP),” Dr. Pillar said. “These patients were older and had more severe OSA.”
In terms of new cardiovascular conditions, 28% of patients had developed dyslipidemia during follow-up, 15% had developed hypertension, 12% had developed angina pectoris, 7% had developed diabetes, 2% had experienced a stroke, and 1% had developed arrhythmia. None experienced a myocardial infarction.
When the number of new conditions per patient was totaled, 73% of the patients had not developed any new conditions, 15% had developed one, 9% had developed two, and 3% had developed three.
There was a significant correlation between poorer endothelial function at baseline and a greater number of new cardiovascular conditions at follow-up, according to Dr. Pillar.
In multiple regression analyses, endothelial dysfunction was the strongest significant determinant of new cardiovascular morbidity. It was followed by body mass index and time since OSA diagnosis. Respiratory disturbance index was a marginally significant predictor.
A variety of other factors (age, total sleep time, and extent of oxygen desaturation) were not significant determinants of cardiovascular morbidity.
Study limitations included the insufficient power to compare the CPAP group with the untreated group, and the lack of data on potential confounders such as pulmonary hypertension, Dr. Pillar said.
“Endothelial dysfunction, body mass index, time of follow-up, and respiratory disturbance index are predictive of cardiovascular complications in patients with OSA,” he concluded, adding that future research in this cohort may help to better clarify the mechanisms of these observed associations.
Dr. Pillar reported that he is a consultant and member of the speakers bureau for Itamar Medical Ltd., which manufactures the device used to assess endothelial function.