HMN 2026: How Sleep patterns may reveal hidden heart risks

People whose sleep apnea changes dramatically from night to night are 30% more likely to have a heart attack, stroke, or heart failure, reveals a new study from Flinders University. The research, published in the journal SLEEP, shows that it is not just how severe sleep apnea is that matters, but how much it fluctuates, with wide night-to-night swings in breathing problems during sleep linked to a higher risk of serious heart disease.

Why fluctuating apnea matters

Obstructive sleep apnea causes repeated pauses in breathing during sleep and affects millions of people worldwide. It is commonly associated with loud snoring, restless sleep, and daytime fatigue, but it is also closely linked to heart disease and stroke. Most people tested for sleep apnea only have their breathing measured on one night, and this single snapshot may not be representative in people whose condition varies substantially night-to-night.

The study analyzed sleep data from more than 3,000 adults who tracked their breathing at home using an under-mattress sensor. Their sleep patterns were measured over several months and compared with reported heart and stroke conditions.

What the researchers discovered

Lead author and sleep expert, Dr. Bastien Lechat, from FHMRI Sleep Health, says people whose sleep apnea severity varies from night to night were about one third more likely to have experienced a heart attack, stroke, or heart failure, even after accounting for average sleep apnea severity.

“Many people assume sleep apnea is stable, but the reality is very different, and some nights can be much worse than others, and this repeated up and down strain may place extra stress on the heart,” says Dr. Lechat. “A single night sleep test may falsely reassure some patients, because people with mild average sleep apnea can still be at higher risk if their breathing problems swing dramatically between nights.”

Matthew Flinders Professor Danny Eckert, Director of FHMRI Sleep Health and senior author on the paper, says the findings help explain why heart risk can be difficult to predict in people with sleep apnea.

Clues from a second study

“The body may struggle to adapt to repeated changes in oxygen levels and sleep disruption. These night-to-night swings can quietly stress the heart and blood vessels over time without being picked up by standard testing,” says Professor Eckert.

The findings are reinforced by a second large international Flinders-led study, published in npj Digital Medicine, that tracked nearly 30,000 people over several years using home-based digital health devices. This study found that more severe sleep apnea, high night to night variability, and even habitual snoring were all linked to faster aging of the blood vessels, an early warning sign for cardiovascular disease.

Importantly, the study led by Dr. Lucia Pinilla, found that people with mild sleep apnea but high nightly variability had blood vessel health similar to those with severe sleep apnea, highlighting a hidden group at risk.

Why multi-night monitoring matters

Dr. Pinilla says the two studies together show why repeated sleep monitoring is so important. “These findings show that one-night tests can miss people at real risk. Sleep should be seen as a moving picture rather than a single photograph, and understanding nightly patterns can help doctors better identify who needs early intervention,” she says.

Heart disease remains the leading cause of death globally, and many risk factors are preventable. The researchers say better sleep assessment could become an important tool for identifying cardiovascular risk earlier and tailoring treatment more effectively.

The studies also highlight the growing role of home-based health technology, which allows sleep and heart health to be monitored over long periods in real world settings.

Implications for future care and research

Professor Eckert says multi-night monitoring mirrors how other chronic conditions are managed. “Blood pressure and blood sugar are measured repeatedly over time, and sleep health should be treated the same way,” he says.

The researchers stress the studies do not prove that sleep apnea variability directly causes heart disease. However, they say the strong and consistent associations show the need for longer term studies and changes to how sleep apnea is assessed.

“If you snore or feel unrefreshed after sleep, speaking with a health professional could help uncover hidden risks to your heart and there are many options available for treatment,” says Dr. Lechat.

Key medical concepts

Obstructive sleep apneaCardiovascular Diseases