New research from Flinders University suggests that how much your sleep apnea varies from night to night may matter as much as how severe it is. Multi-night home monitoring could help uncover hidden heart risks that one-night sleep tests miss.
People whose sleep apnea swings dramatically from one night to the next may face a significantly higher risk of heart attack, stroke or heart failure, according to new research from Flinders University.
The findings suggest that doctors may be missing a hidden group of patients at risk because most sleep apnea tests capture only a single night of data.
In one study, published in the journal Sleep, researchers analyzed sleep data from more than 3,000 adults who tracked their breathing at home using an under-mattress sensor. The participants’ sleep patterns were recorded over several months and then compared with reports of heart and stroke conditions.
The team focused not just on how severe people’s obstructive sleep apnea was on average, but on how much it fluctuated from night to night. Obstructive sleep apnea causes repeated pauses in breathing during sleep and is often linked with loud snoring, restless nights and daytime fatigue. It is also closely associated with cardiovascular disease.
Lead author Bastien Lechat, a sleep expert at Flinders Health and Medical Research Institute (FHMRI) Flagship Sleep Health Program, found that people whose sleep apnea severity varied widely between nights were about one-third more likely to have experienced a heart attack, stroke or heart failure, even after accounting for their average level of sleep apnea.
Lechat noted many people and clinicians may be underestimating how much sleep apnea can change.
“Many people assume sleep apnoea 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,” he said in a news release.
That variability matters for diagnosis, he explained.
“A single night sleep test may falsely reassure some patients, because people with mild average sleep apnoea can still be at higher risk if their breathing problems swing dramatically between nights,” he said.
Senior author Danny Eckert, the director of FHMRI Sleep Health and a Matthew Flinders Professor at Flinders University, said the results help explain why heart risk can be hard to predict in people with sleep apnea.
Eckert noted that the body may not cope well with constantly changing oxygen levels and broken sleep.
“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,” he said in the news release.
A second large study led by Flinders researchers, published in npj Digital Medicine, reinforces the message that night-to-night patterns matter.
In that international project, nearly 30,000 people were tracked over several years using home-based digital health devices. The researchers looked at sleep-disordered breathing, including sleep apnea and habitual snoring, and signs of vascular aging — changes in blood vessels that can signal early cardiovascular disease.
The study, led by Lucia Pinilla, a research fellow at FHMRI Sleep Health, found that more severe sleep apnea, high night-to-night variability and even regular snoring were all linked with faster aging of the blood vessels. Importantly, people with mild sleep apnea but high nightly variability had blood vessel health similar to those with severe sleep apnea, pointing to a group whose risk might be overlooked in standard testing.
Pinilla said the two studies together show why repeated sleep monitoring is crucial.
“These findings show that one night tests can miss people at real risk,” she said in the news release. “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.”
Heart disease remains the leading cause of death worldwide, but many of its risk factors — including high blood pressure, smoking, obesity and untreated sleep disorders — can be addressed. The Flinders team argues that better sleep assessment could become an important tool for spotting cardiovascular risk earlier and tailoring treatment.
The research also highlights how home-based health technology is changing the way sleep and heart health can be monitored. Under-mattress sensors and other digital devices allow scientists and clinicians to collect data over weeks or months in people’s everyday environments, rather than relying solely on a single night in a sleep lab.
Eckert said this approach mirrors how other chronic conditions are already managed.
“Blood pressure and blood sugar are measured repeatedly over time, and sleep health should be treated the same way,” he said.
For patients, the message is not to panic, but to pay attention. Loud snoring, gasping during sleep, morning headaches and feeling unrefreshed despite a full night in bed can all be signs of sleep apnea. Because the condition often goes undiagnosed, many people may not realize that their sleep could be putting extra strain on their heart and blood vessels.
The researchers stress that their studies are observational, meaning they show strong associations but do not prove that variable sleep apnea directly causes heart disease. Other factors, such as weight, lifestyle or existing health conditions, may also play a role.
Even so, the consistent links between night-to-night variability, blood vessel aging and cardiovascular problems point to the need for longer-term studies and a rethink of how sleep apnea is assessed in clinics.
If future research confirms that swings in sleep apnea severity actively damage the heart and blood vessels, multi-night home monitoring could become a standard part of care. That might help doctors identify high-risk patients earlier, adjust treatments such as continuous positive airway pressure (CPAP) more precisely, and track whether interventions are working over time.
For now, the researchers encourage anyone who snores heavily, wakes up choking or gasping, or feels persistently tired despite going to bed on time to talk with a health professional.
“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,” Lechat said.
Source: Flinders University