Research consistently shows that sleeping in a cool environment—within the 15–22°C (59–72°F) range for most healthy adults—delivers far greater benefits than a warm room. However, a slight adjustment to this range ensures comfort without sacrificing sleep quality for seniors, infants, and anyone who’s sick.

Why Do You Sleep Better in Cold?

The answer is cold. A cool bedroom doesn’t just “feel nice”—it aligns with how your body is designed to rest. Here’s the science behind why cooler temperatures lead to better sleep:

It syncs with your circadian temperature rhythm

Your body has an internal clock (your circadian rhythm) that regulates everything from energy levels to sleep—and temperature plays a starring role. Throughout the day, your core temperature rises slightly to keep you alert, focused, and active. But 1–2 hours before bed, your brain sends a clear signal: it triggers a 1–2°C (2–4°F) drop in core temperature. This drop slows your metabolism, relaxes your muscles, and tells your body, “It’s time to wind down.”

It boosts sleep quality (and cuts down on “micro-awakenings”)

Cool rooms solve “micro-awakenings”—brief, unremembered moments where you rouse from sleep. By keeping your body at a comfortable, steady temperature, they reduce nighttime awakenings and boost “sleep efficiency”—the percentage of time you spend actually sleeping (vs. lying awake or stirring). Multiple studies back this up: people who sleep in cool environments (within the 15–22°C range) report 15–20% more deep sleep and fewer disruptions like tossing, turning, or waking up to adjust the covers.

It supports long-term health

The benefits of cool sleep don’t stop at better rest—they extend to your physical health too. Here are two key advantages:

• Improved glucose metabolism: Sleeping in a cool room for just one week led to a 10% drop in fasting blood glucose (a key marker of blood sugar control) and enhanced insulin sensitivity (how well your body uses insulin to process sugar) compared to people who slept in 24°C (75°F) rooms.

• Lower heart disease risk: . Setting bedroom temperatures to 14–15°C (57–59°F) not only improved glucose metabolism but also reduced risk factors for heart disease—all while creating optimal conditions for restful sleep.

Ideal Sleep Temperature Differs From Person to Person

While 15–22°C (59–72°F) works for most adults, some groups benefit from slightly warmer temperatures. Here’s who needs adjustments, and why:

• Seniors: 20–25°C (68–77°F). Older adults often have trouble regulating their body temperature due to age-related changes: their skin may be thinner, blood circulation can slow down, and they may produce less body heat at night. This makes them more susceptible to feeling cold—and cold temperatures can disrupt their sleep or even increase the risk of hypothermia in extreme cases.A study from the Marcus Institute for Aging Research confirms this: it found that the optimal sleep temperature for seniors is between 20–25°C (68–77°F). This slightly warmer range keeps older adults comfortable without overheating, helping them stay asleep longer and wake up more refreshed.
• Infants: 20–22°C (68–72°F). Babies (especially newborns) can’t regulate their body temperature as well as adults—they lose heat quickly through their heads and have less body fat to insulate them. A room that’s too cold can put them at risk of hypothermia, while a room that’s too warm increases the risk of sudden infant death syndrome (SIDS). The American Academy of Pediatrics (AAP) recommends a bedroom temperature of 20–22°C (68–72°F) for infants. This range keeps them warm enough to stay comfortable but cool enough to reduce SIDS risk. To check if your baby is too hot or cold, feel their chest or back (not their hands or feet—these are often cold due to poor circulation). If their skin feels sweaty or hot, the room is too warm; if it feels cool to the touch, add a light layer (like a swaddle) or adjust the thermostat slightly.
• When You’re Sick: Slightly Warmer Than Normal. If you have a cold, flu, or fever, your body’s temperature regulation is already off—so your ideal sleep temperature may shift. A slightly warmer room (around 22–24°C (72–75°F)) can help: it soothes congestion (warm air loosens mucus), eases muscle aches, and prevents you from feeling chilled (a common side effect of fevers). That said, don’t overdo it. A room that’s too warm can make you sweat excessively, dehydrate you, or worsen fever symptoms. Aim for “comfortably warm”—not hot—and adjust based on how you feel (e.g., if you’re sweating, turn down the heat a degree or two).

Tips for Cooler Sleep

You don’t need a fancy smart thermostat to create a cool, sleep-friendly bedroom—though it helps! Here are simple, actionable tips to adjust your space:

Choose the right bedding (and covers)

• Mattress & pillow covers: Opt for covers made of moisture-wicking, breathable fabrics like cotton, linen, or Tencel. These materials pull sweat away from your body, keeping you cool and dry all night. Avoid plastic or synthetic covers—they trap heat and moisture.

• Sheets & blankets: For warm nights, use lightweight cotton sheets (they’re breathable and soft). For cooler nights, switch to lightweight cotton flannel— it’s warm but not heavy, so you won’t overheat. Avoid thick, fuzzy blankets unless the room is very cold.

• Pillows: A breathable memory foam pillow (look for ones with ventilation holes) or a down-alternative pillow can help—they don’t hold heat like dense, non-breathable pillows.

Block sunlight (and heat) during the day

Sunlight streaming through windows can raise your bedroom temperature by several degrees—even on cool days. To keep the room cool, install:

• Blackout curtains: They block sunlight completely, keeping the room dark (great for circadian rhythm!) and cool.

• Reflective window film: Available at most home stores, this film reflects sunlight away from your windows, reducing heat gain without blocking all light.

Use fans, AC, or heaters strategically

• Fans: Even if the room is cool, a fan can help. It circulates air, creating a “wind chill” effect that makes you feel cooler. Place it near your bed (but not directly on you) for best results.

• AC: In hot weather, set your AC to 18–20°C (65–68°F)—this is within the optimal range and won’t waste energy. Use a programmable thermostat to lower the temperature 1–2 hours before bed, then raise it slightly in the morning.

• Heaters: For seniors or cold nights, use a space heater to keep the room within the ideal range. Choose one with a thermostat (to avoid overheating) and place it away from bedding or curtains (for safety).