Summer Heat & Sleep: Why Hot Nights Worsen Sleep Apnoea Symptoms

When summer rolls in, most of us brace for hot days. But it’s the hot nights that often do the most damage to our sleep. And for people living with obstructive sleep apnoea (OSA), warm nights are more than just uncomfortable. Growing evidence shows they can significantly worsen symptoms ^{1, 2}. As temperatures continue to rise globally, understanding how heat affects sleep quality is becoming increasingly important ^{1, 2}.

A major global study involving more than 116,000 people and 62 million nights of sleep data found that high ambient temperatures have a striking effect on sleep apnoea severity ¹. On extremely hot nights, which is around 27.3°C, researchers observed a 45% increase in the likelihood of OSA occurring compared with cooler nights around 6.4°C ¹. This isn’t a small shift. It means that as temperatures rise, the number of nights affected by apnoea substantially increases, even in people who may not have symptoms every night.

In another study, a large multi-country study across 17 European nations found that during summer heatwaves, cases of moderate-to-severe OSA increased by 13%, and for every 1°C rise in nighttime temperature, OSA symptoms rose by an additional 1.1% ². The risk was even greater when humidity was high, creating a sticky, heavy environment that makes breathing during sleep even harder.

Why does heat have such a powerful impact? Scientists suggest several mechanisms. Hot nights fragment sleep and make it harder to reach deep, restorative stages ². Heat can also cause fluid retention and dehydration, which may worsen upper airway collapse in people who are prone to snoring and apnoeas ^{1, 2}. On top of that, some using CPAP therapy may find it less comfortable on hot nights and may skip or shorten their treatment on the very nights they need stable breathing the most ².

Seasonal trends reinforce this pattern. A study of around 70,000 people with OSA found that OSA severity was about 5% higher in summer and winter than in spring and autumn in the northern hemisphere, and 10–15% higher in summer compared to cooler months in Australia ³. In Australia, AHI (Apnoea-Hypopnea Index) was lowest from February to April and climbed steadily to reach its highest levels in the summer months of December and January, suggesting that hotter weather and seasonal changes in sleep patterns both play a role ³.

As Australia faces longer, hotter summer periods, it’s worth paying close attention to how warm nights may be affecting your breathing and sleep quality. If you notice your sleep getting worse when the temperature rises including louder snoring, choking or gasping at night, waking unrefreshed, morning headaches or nodding off during the day, it’s worth taking it seriously.

Simple steps like cooling your bedroom, using a fan, staying well hydrated and sticking with your CPAP or other prescribed therapy through the summer can all help protect your sleep quality. Most importantly, if you or your bed partner notice possible OSA symptoms, especially during hot nights, speak with your doctor or a sleep and respiratory specialist about assessment and treatment. Getting on top of sleep apnoea early can protect your heart, brain and daytime performance for years to come.

How Sove CPAP Clinic Can Help

Founded in 2008, Sove CPAP Clinic has grown to become a leading provider of respiratory and sleep services and products in Australia, with over 80 clinics nationwide. Our comprehensive clinical team includes Respiratory & Sleep Specialists, Sleep Technologists, and CPAP Consultants, ensuring that you receive comprehensive and personalised care. All medical procedures, including sleep studies and lung function testing, are bulk billed to all Australians, with minimal wait time. If you would like to speak to a Respiratory & Sleep Physician, book a bulk-billed sleep study, or seek advice for your sleep apnoea, you can reach us at 1300 76 29 39 or info@thecpapclinic.com.au.

ALWAYS FOLLOW THE DIRECTIONS FOR USE. CPAP is used for Obstructive Sleep Apnoea treatment. When considering whether a sleep study or CPAP is right for you, speak to your doctor. Medicare criteria and T&Cs apply.

References

[1] Lechat, Bastien, et al. “Global Warming May Increase the Burden of Obstructive Sleep Apnea.” Nature Communications, vol. 16, no. 1, 16 June 2025, www.nature.com/articles/s41467-025-60218-1, https://doi.org/10.1038/s41467-025-60218-1.

[2] News Desk. “Heatwaves Linked to Rise in Sleep Apnoea Cases in Europe.” Flinders University, 30 Oct. 2025, news.flinders.edu.au/blog/2025/10/30/heatwaves-linked-to-rise-in-sleep-apnoea-cases-in-europe/. Accessed 7 Dec. 2025.

[3] Bastien Lechat, et al. “Obstructive Sleep Apnea Severity Varies by Season and Environmental Influences such as Ambient Temperature.” Communications Medicine, vol. 5, no. 1, 29 July 2025, pp. 314–314, https://doi.org/10.1038/s43856-025-01016-0.