How does fabric choice affect your body temperature and sleep?

Fabric has a profound effect on thermoregulation, which is your body's ability to maintain a stable core temperature. Synthetic fabrics like polyester and nylon are poor thermal regulators because they do not absorb moisture and do not allow adequate airflow. They trap heat in warm conditions and can feel clammy in cool ones, forcing your body to work harder to maintain equilibrium. This is especially disruptive during sleep, when your core temperature naturally drops by one to two degrees to initiate and maintain deep sleep stages.

Studies on sleep quality have found that sleepwear and bedding material directly affect sleep onset, duration, and depth. Sleeping in polyester sheets or synthetic pajamas can cause overheating and night sweats, leading to fragmented sleep and reduced time in restorative deep-sleep and REM stages. Conversely, natural fibers like cotton, linen, silk, Tencel, and merino wool actively regulate microclimate by absorbing and releasing moisture vapor, keeping the skin surface drier and the temperature more stable.

For sleep in particular, choosing natural-fiber bedding and sleepwear is one of the highest-impact changes you can make. Promeed offers silk pillowcases and sleep sets that excel at temperature regulation, while Organic Basics and Mate the Label make sleepwear from Tencel and organic cotton designed for overnight comfort. At ONDU, our sleep vertical is built around this principle: what you sleep in matters as much as how long you sleep.