Gender differences in sleep quality under summer thermal conditions: a case Study in a Qingdao dormitory

Thermal environments significantly influence sleep quality, yet gender-related differences under real summer conditions in cold climate zones remain underexplored. The present study conducted a field experiment in university dormitories in Qingdao, China, involving 30 healthy adults (15 males, 15 females) during summer 2024 and 2025. Indoor air temperature(Ta), relative humidity(RH), and CO₂ levels were continuously monitored, while mean skin temperature (MST)and sleep quality indicators were recorded using iButton sensors and Fitbit wristbands. Subjective thermal sensation and preference were assessed before sleep and after awakening. Statistical analysis included t-tests and multiple regression with interaction terms. Results showed that females had higher MST (34.62 °C) than males (34.42 °C) throughout the night and required higher neutral temperatures in Experimental Periods Ⅰ (ΔT ≈ +0.87 °C) and Experimental Periods Ⅲ(ΔT≈+0.02 °C). An increase of 1 °C in indoor Ta reduced deep sleep duration by 9.23 min for males and 10.58 min for females. Higher RH was associated with increased wake after sleep onset in females (+1.14 min/%RH) and reduced rapid eye movement duration in males (–1.80 min/%RH). These findings highlight gender-specific thermal comfort differences during sleep under air-conditioned summer conditions, with practical implications for energy-efficient indoor climate control and the design of personalized sleeping environments.