Scientists from Scripps Research have found that an irregular sleep schedule—even with shifts of just one hour—is associated with an increased risk of arterial hypertension and obstructive sleep apnea. The study’s results were published in the Journal of Medical Internet Research (JMIR).

About 400 adults took part in the study. Over an average period of nearly two years, they shared data from wearable fitness devices that tracked sleep parameters and completed medical questionnaires. This extended follow-up made it possible to identify stable sleep habits that often go unnoticed in short-term studies.

Data analysis showed that people whose bedtimes and wake-up times varied significantly from night to night had more than twice the risk of sleep apnea compared with those who maintained a consistent schedule. Sleep apnea is a breathing disorder characterized by brief pauses in breathing during sleep. These episodes of hypoxia can disrupt heart rhythm and negatively affect brain function.

The likelihood of elevated blood pressure with an irregular sleep schedule also increased by 71%. Importantly, the decisive factor was not the total duration of sleep, but the absence of “shifts” in sleep timing.

The authors note that irregular sleep may be a marker of underlying cardiovascular dysfunction. They suggest that data from wearable devices could potentially be used for early detection of hypertension risk and sleep-related breathing disorders. At the same time, the researchers emphasize that the observed association is observational and does not prove a direct cause-and-effect relationship; further clinical studies are needed to establish causality.