Does Bedroom Heat Above 25°C Cut Sleep Efficiency?

Short answer: often yes for sleep efficiency, especially once nights leave the mid-20s°C. In a 2023 longitudinal study in Science of the Total Environment, Baniassadi and colleagues tracked nearly 11,000 person-nights in 50 community-dwelling older adults. Sleep was most efficient and restful when nighttime bedroom temperature sat between 20 and 25°C. As temperature rose from 25°C to 30°C, models showed a clinically relevant 5-10% drop in sleep efficiency. That is a bedroom-air finding about thermoregulation and continuity, not a humidity or product claim.

The same models also predicted about 60 minutes less total sleep time as temperature climbed from 22°C to 30°C. Individual optima still varied, so the useful takeaway is a band, not a single magic number.

What did Baniassadi et al. measure at home?

Researchers at Hebrew SeniorLife's Marcus Institute for Aging Research and Harvard Medical School monitored older adults (mean age about 79) in their own Boston-area homes with bedroom environmental sensors and wearable sleep rings. After cleaning outliers, the analysis covered 10,903 person-nights from 50 participants. Outcomes included sleep efficiency (time asleep divided by time in bed), total sleep time, and restlessness, with models adjusting for humidity, day length, weekend status, and baseline health, function, and socioeconomic factors.

| Bedroom temperature and sleep (Baniassadi et al., 2023) | Finding | | --- | --- | | Most efficient / restful range | 20-25°C nighttime ambient | | Sleep efficiency, 25°C → 30°C | about 5-10% lower | | Total sleep time, 22°C → 30°C | about 60 minutes less | | Sample | 50 older adults; 10,903 person-nights | | Shape of relationship | mostly nonlinear; large between-person differences |

The authors note that a 5-10% efficiency drop is large enough, in prior work they cite, to matter for next-day cognition, activity, stress, and mood. They also caution that optima differ between people, so personalization matters.

Does warmer outdoor temperature also shorten deep sleep?

A much larger 2025 Nature Communications study by Li and colleagues adds a population-scale layer. Using about 23 million days of wearable sleep monitoring from 214,445 adults across mainland China, they found that each 10°C rise in daily mean temperature linked to:

• 20.1% higher odds of sleep insufficiency (under 7 hours)
• 9.67 minutes less total sleep
• 2.82% lower deep-sleep share of the night

Effects were stronger among older adults, women, people with higher BMI, and higher-humidity days. The exposure here is outdoor daily mean temperature assigned to residence, not bedroom sensors, so it answers a related question: warmer ambient conditions associate with shorter and compositionally lighter sleep at scale. Together with Baniassadi's in-home sensors, the pattern is consistent: heat pressure tends to cost efficiency, duration, and deep sleep.

What bedroom temperature do sleep organizations recommend?

Institutional guidance sits cooler than many warm-climate bedrooms. The National Sleep Foundation's sleep tips advise a bedroom between 60 and 67°F (about 15.5-19.4°C) because body temperature naturally falls to initiate sleep. Sleep Foundation's bedroom-temperature overview commonly cites about 65°F (18.3°C) as a practical adult target, with roughly 65-68°F as a comfortable band for many people.

Those targets describe air setpoints that support the nocturnal core-temperature drop. They are not medical prescriptions, and older adults in Baniassadi's sample still slept well across a slightly warmer 20-25°C window. The shared idea is simple: keep the room cool enough that core body temperature sleep physiology is not fighting a hot microclimate all night.

How does cooling bedding fit body-temperature science?

Room air is only one layer. Bedding and sleepwear shape the microclimate next to skin, which is where heat leaves the body. For hot sleeper bedding nights, lighter covers, breathable fabrics, and cooling fabric sleep materials can reduce trapped warmth even when the thermostat cannot reach a textbook setpoint. That is thermoregulation sleep hygiene: help heat leave the core and stay away from sticky wake-ups.

In humid tropical cities such as Singapore, outdoor nights often sit well above NSF's cool-room band. Fans, timed cooling early in the night, and bedding that does not hold heat become practical levers when the room cannot stay at 18°C. People who like steady pressure sometimes use a weighted blanket; those who run warm may prefer a cooling weighted blanket so deep pressure does not come with extra insulation. Those choices are comfort tools for sleep quality and settling, not treatments that rewrite the Baniassadi or Li statistics.

Details on fabric and weight live on specifications and shop if you are comparing options. This article does not claim any brand changes sleep efficiency by a fixed percent.

What is the takeaway?

Does bedroom heat above 25°C cut sleep efficiency? In Baniassadi et al. 2023, sleep was most efficient at 20-25°C, and efficiency fell about 5-10% from 25°C to 30°C, with about an hour less modeled total sleep from 22°C to 30°C across nearly 11,000 person-nights. Li et al. 2025 extend the heat story at population scale: each 10°C of warmer daily temperature linked to higher odds of short sleep, less total sleep, and a smaller deep-sleep share. NSF and Sleep Foundation still point adults toward cool bedrooms in the mid-60s°F. Protect a cool sleep opportunity first; treat bedding as a microclimate helper for hot nights, not a substitute for air that stays in a sleep-friendly band.

Sources

1. Baniassadi A, Manor B, Yu W, Travison T, Lipsitz L. Nighttime ambient temperature and sleep in community-dwelling older adults. Science of the Total Environment. 2023;899:165623. doi:10.1016/j.scitotenv.2023.165623. https://pmc.ncbi.nlm.nih.gov/articles/PMC10529213/ ; https://www.sciencedirect.com/science/article/pii/S0048969723042468

1. Marcus Institute for Aging Research / Hebrew SeniorLife. Optimal sleep temperature for seniors is between 68 to 77 degrees Fahrenheit, study reveals. 28 Aug 2023. https://www.marcusinstituteforaging.org/news/optimal-sleep-temperature-seniors-between-68-77-degrees-fahrenheit-study-reveals

1. Li A, Luo H, Zhu Y, et al. Climate warming may undermine sleep duration and quality in repeated-measure study of 23 million records. Nature Communications. 2025;16. doi:10.1038/s41467-025-57781-y. https://www.nature.com/articles/s41467-025-57781-y

1. National Sleep Foundation. Sleep tips (bedroom temperature 60-67°F). https://www.thensf.org/sleep-tips/

1. Sleep Foundation. Best temperature for sleep (about 65°F / 65-68°F adult guidance). Updated 11 Jul 2025. https://www.sleepfoundation.org/bedroom-environment/best-temperature-for-sleep