Excessive daytime sleepiness (EDS)—a commonality among heart patients and those with sleep-disordered breathing (SDB)—could be an independent predictor of adverse cardiovascular events and repeat myocardial infarction (MI), researchers  reported this month in the Journal of the American Heart Association.

EDS, regardless of its root cause, can be an everyday danger, first author Jiang Xie, MD, PhD, and colleagues wrote. The disorder is linked to a higher hazard of occupational injuries, car accidents, cardiovascular disease (CVD) and cerebrovascular disease, and it’s also closely tied to CVD risk factors like obesity, diabetes, uncontrolled hypertension and physical inactivity.

And EDS is far from a rarity in the cardiology department—nearly a third of all MI patients develop the condition.

Xie et al. followed a cohort of 104 MI patients for a total of 48 months for their study, ranking each participant for sleepiness based on the Epworth Sleepiness Scale. The ESS, a simple indicator of daytime fatigue in adults, produces a score between zero and 24, with the latter being the highest indication of sleepiness. In Xie’s study, EDS was defined as an ESS score of 11 or greater.

Over the course of the four-year trial, EDS patients saw a much higher rate of major adverse cardiac events than their non-EDS counterparts, the authors wrote—48.4 percent versus 27.4 percent, respectively. Participants with EDS were also 29 percent more likely to experience reinfarction than those without the condition, who saw a 5.5 percent risk. An EDS patient’s crude risk of adverse cardiac events proved 2.15 times higher, as well, when calculated with a Cox proportional hazards model.

EDS seemed to occur in MI patients regardless of SDB status, Xie and co-authors found, but disordered breathing isn’t the only contributor to a poor risk profile. EDS patients’ issues could also stem from poor sleep, shortened sleep or insomnia.

Xie and colleagues said in the paper it could be especially helpful in a clinical setting to evaluate sleepy, post-MI patients with extra care.

“Because of the strong prognostic implications of EDS in patients with moderate to severe sleep-disordered breathing, we suggest routine evaluation of patients with myocardial infarction to identify those who are at risk and who may need intervention, such as continuous positive airway pressure,” they wrote. “Larger clinical trials are warranted to evaluate strategies to alleviate EDS and the effect on long-term prognosis."