Estée Lauder teamed up with UH Case Medical Center to evaluate how sleep—or a lack thereof—affected the skin of 60 women. Turns out, those who slept only 5 hours every night for a month had twice as many wrinkles and spots, compared to those who slept for 7 hours. They also recovered from sunburn significantly slower than those who clocked in more zzz’s. The findings were presented in May at the International Investigative Dermatology meeting in Edinburgh, Scotland. “At night, energy and cellular functions focus on repair and recovery in order to prepare the skin to defend itself against the environment the next morning,” explains Nadine Pernodet, PhD, executive director of skin biology, research and development at Estée Lauder. Less sleep means less repair, and even less defense, causing wrinkles over time. Experts suggest clocking in seven hours of sleep for optimal skin health. Too busy tossing and turning? Try these 20 Ways To Sleep Better Every Night. More from Prevention: 5 Ways To Wake Up To Better Skin