Hot or cold? Understanding your body's needs at night

Some people kick off the duvet in the early hours. Others never really warm up. These differences are not trivial – they reveal how your body manages its own thermal regulation during the night.

The body and temperature

Falling asleep is linked to a drop in core body temperature. At the end of the day, the body begins to redistribute its heat to the extremities – hands and feet – to dissipate it and lower its internal temperature. This process promotes melatonin production and prepares the nervous system for rest.

During the night, this temperature continues to evolve. It reaches its lowest level around 4 AM, then gradually rises until waking. The environment in which one sleeps must support this natural movement – neither hindering nor disrupting it.

Those who are too hot

Some people naturally tend to produce more body heat, or to dissipate it poorly. This is often the case for people with a high metabolism, but also during certain hormonal phases – pregnancy, menstrual period, perimenopause. The external environment also plays a role: a poorly ventilated room, synthetic bedding that prevents breathing, or an overly enveloping memory foam mattress can worsen the sensation of heat.

The result manifests as frequent nocturnal awakenings, restlessness during sleep, or fatigue upon waking despite a satisfactory night's sleep duration.

Those who are cold

The extreme opposite also exists. Some people struggle to fall asleep because their extremities remain cold, which reflects a difficulty for the body to effectively redistribute heat. Slower peripheral circulation, chronic stress, or simply a constitutional tendency can be the cause.

For these individuals, the solution is not necessarily to heat the room more – which would disrupt the general thermal balance – but rather to focus on the comfort of the extremities: light socks, a hot water bottle at the feet, and bedding materials that are both soft and insulating.

Solutions

In both cases, the thermal environment of the bedroom should be between 16 and 19 degrees Celsius – a range that sleep research considers optimal for most people. But room temperature is only part of the equation.

Materials in direct contact with the body have a considerable impact. Natural fibers – linen, organic cotton, fine merino wool – have the property of adapting to thermal variations: they absorb moisture when the body heats up, and release warmth when it cools down. This is called thermoactivity.

Choosing your sheets, duvet, or pillow according to your thermal profile is one of the most direct – and most underestimated – interventions on sleep quality. No complex device is needed. Just materials that work with the body rather than against it.