Effects of ambient temperatures on sleeping thermal comfort and respiratory immunity: A winter field study in college students

Abstract

The thermal environment can affect human thermal comfort during sleep and is closely related to health. Using salivary immunoglobulin E (IgE) as a biomarker to measure respiratory immunity, this study investigated the effects of ambient temperatures on sleeping thermal comfort, physiological parameters and salivary IgE concentrations of college students in winter. The experiment was conducted at three different ambient temperatures (14.7 ± 0.3 °C, 17.2 ± 0.4 °C, and 20.1 ± 0.7 °C). Data on the thermal sensation vote (TSV) and thermal comfort vote (TCV) of the subjects (8 males and 6 females) were collected, and the skin temperatures of seven body parts were measured. In addition, saliva was collected before and after sleep to detect IgE concentrations in the human body. By combining subjective votes and objective physiological parameters, this paper revealed the sleep temperature range that might improve human respiratory immunity in winter, which was within the human thermal comfort zone. The results showed that the nondimensional IgE concentration was 49.78% higher after sleep than before sleep. Furthermore, the variation at 20.1 °C was relatively significant (P < 0.05), and the TSV was 0.86 and the TCV was 1.09 during sleep. It was also found that the Δ nondimensional IgE concentration was significantly correlated (P < 0.01) with ΔThead (Δ indicates the change from before sleep to after sleep). Therefore, a comfortable and slightly warm ambient temperature range of the bedroom in winter may help to improve human respiratory immunity. This conclusion is of great significance to the development of smart air-conditioning aiming at creating a comfortable and healthy sleep environment.