Adults with obstructive sleep apnoea (OSA), who experience excessive sleepiness while awake are at greater risk for cardiovascular diseases (CVD) than those who do not experience such symptoms, says a new study.

Sleep apnoea is a potentially serious sleep disorder in which breathing repeatedly stops and starts. Adults with moderate to severe OSA were categorised into four subtypes according to the symptoms they report: disturbed sleep, minimally symptomatic, moderately sleepy and excessively sleepy.

"Multiple studies from our group have shown that patients with moderate to severe OSA throughout the world can be categorised into specific subtypes based on their reported symptoms," said Diego R. Mazzotti, researcher at the University of Pennsylvania in the US.

"However, until now, it was unclear whether these subtypes had different clinical consequences, especially in regard to future cardiovascular risk," said Mazzotti. For the current study, researchers followed for nearly 12 years 1,207 adults, aged 40 or above. Participants reported symptoms such as difficulty in falling and staying asleep, snoring, fatigue, drowsy driving and daytime sleepiness.

The findings, published in the American Journal of Respiratory and Critical Care Medicine, showed that participants exhibiting the excessively sleepy subtype were more than three times as likely to have been diagnosed with heart failure than the other three subtypes.

They were about twice as likely to experience a heart attack, heart failure, stroke or cardiovascular death during the follow-up period than the other three subtypes. In addition, they were also more likely to experience a new or recurrent cardiovascular event during the follow-up period.

The increased risk of CVD associated with OSA appears to be driven by patients in the excessively sleepy subtype, according to the researchers. Studies of the cardiovascular benefits of continuous positive airway pressure, or CPAP, treatment for OSA should focus on the excessively sleepy subtype, who are likely to benefit the most from what is considered the gold standard OSA treatment, the team suggested.