Adults with obstructive sleep apnea (OSA) who experience excessive sleepiness while awake appear to be at far greater risk for cardiovascular diseases than those without excessive daytime sleepiness, according to new research published online in the American Thoracic Society’s American Journal of Respiratory and Critical Care Medicine.
In “Symptom Subtypes of Obstructive Sleep Apnea Predict Incidence of Cardiovascular Outcomes,” Diego R. Mazzotti, PhD, and coauthors report on a study of adults with moderate to severe OSA who were categorized into 4 subtypes according to the symptoms they report: disturbed sleep, minimally symptomatic, moderately sleepy, and excessively sleepy.
Previous studies have linked OSA and cardiovascular disease. To understand this association better, researchers have begun to categorize patients with OSA based on their symptoms.
“Multiple studies from our group have shown that patients with moderate to severe OSA throughout the world can be categorized into specific subtypes based on their reported symptoms,” says Mazzotti, lead study author and a sleep researcher at the University of Pennsylvania. “However, until now, it was unclear whether these subtypes had different clinical consequences, especially in regard to future cardiovascular risk.”
The current study analyzed data from 1,207 adults participating in the Sleep Heart Health Study, available from the National Sleep Research Resource. Patients were 40 years old or older at enrollment and were followed for nearly 12 years. The patients had moderate to severe OSA, which was defined as having at least 15 episodes per hour while sleeping when they stopped breathing (apnea) or had reduced breathing (hypopnea). The metric is known as the apnea-hypopnea index, or AHI.
Participant-reported symptoms, such as difficulty falling and staying asleep, snoring, fatigue, drowsy driving, and daytime sleepiness, and responses to a widely used questionnaire called the Epworth Sleepiness Scale were used to determine the patient’s subtype.
The study found participants exhibiting the excessively sleepy subtype were:
- More than 3 times as likely to have been diagnosed with heart failure at enrollment than the other 3 subtypes.
- About twice as likely to experience a cardiovascular event (heart attack, heart failure, stroke, or cardiovascular death) during the follow-up