Sleep apnea severity spikes on Saturdays, raising questions about standard weeknight testing

Sleep apnea becomes substantially more severe on weekends compared to weekdays, and the effect is amplified in people who sleep in or shift their sleep schedule on weekends, according to new research published in the American Journal of Respiratory and Critical Care Medicine.

Obstructive sleep apnea (OSA) is a common but serious sleep disorder in which the airway repeatedly collapses during sleep, causing breathing to pause repeatedly through the night. The severity of OSA is typically measured by counting how many times per hour a person’s breathing stops or becomes severely restricted—a figure known as the apnea-hypopnea index, or AHI.

Researchers have long known that OSA severity can vary considerably from night to night, which can cause diagnostic tests—almost always conducted on weeknights—to miss or underestimate the condition in around 20% of patients. What was not known was whether this variability follows a predictable weekly pattern tied to social behaviors.

The researchers behind the new study suspected that the same social factors that disrupt sleep timing across the week might also worsen OSA. Weekend behaviors, including staying up later and sleeping longer than usual, are all known to affect breathing during sleep, and all tend to cluster on weekends. No study had previously examined whether these patterns lead to systematically worse OSA on particular days.

Led by Lucía Pinilla, the team analyzed over three years of sleep data—from January 2020 to September 2023—from 70,052 adult users of a validated under-mattress sleep monitoring device. The sample had an average age of 53 years and was predominantly male (81%), with an average BMI in the overweight range.

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Eligible participants had to use the device regularly enough to provide at least four nights of recorded data per week, at least 28 valid nights per year, and have a yearly average of at least five apnea events per hour. Statistical models were used to estimate the odds of OSA on each day of the week, controlling for individual variation across months and seasons.

The results revealed a clear and consistent pattern, which the researchers have named “social apnea.” Across the entire global sample, the odds of moderate to severe OSA (defined as 15 or more events per hour) were 18% higher on Saturdays compared to Wednesdays. This effect was remarkably consistent across different geographic regions. The effect was stronger in men (21% higher odds) than in women (9%), and stronger in adults under 60 (24%) compared to those aged 60 and over (7%).

When weekend sleep behaviors were taken into account, the picture became even starker: people who slept in by 45 minutes or more on weekends had a 47% further increase in weekend OSA odds, and those with a social jet lag of 60 minutes or more—meaning their sleep timing on weekends was shifted by an hour or more compared to weekdays—experienced a 38% further increase. People with consistent sleep patterns across the week showed no meaningful weekend spike. On average, AHI was 6% higher on weekends compared to weekdays, representing a mean increase of 0.76 events per hour at the group level.

The findings have significant practical implications. They suggest that single-night diagnostic sleep tests—almost universally conducted on weeknights—may systematically underestimate OSA severity for many patients. They also raise questions about CPAP therapy, the leading treatment for OSA, which has historically been considered adequate if used for at least four hours per night on five out of seven nights—an approach that explicitly accommodates lower weekend use.

As the authors note, “non/lower-treatment use on weekends could partially explain our findings,” suggesting that the current CPAP adherence standard may not adequately protect patients during the nights when their OSA is actually at its worst.

The study is not without limitations. The sample consisted of people who chose to purchase a sleep monitoring device, who may differ meaningfully from the general population in their health awareness and lifestyle. Additionally, data on diet, alcohol consumption, smoking, exercise, and CPAP use—factors that could help explain the weekend effect mechanistically—were not available. Furthermore, the device’s ability to detect daytime naps was not evaluated, and defining “weekends” strictly as Friday and Saturday nights may have misclassified participants with non-standard work schedules, such as shift workers.

The study, “‘Social Apnea’: Obstructive Sleep Apnea Is Exacerbated on Weekends,” was authored by Lucía Pinilla, Bastien Lechat, Hannah Scott, Amy C. Reynolds, Jack Manners, Kelly Sansom, Robert Adams, Pierre Escourrou, Peter Catcheside, and Danny J. Eckert.