Bedroom Thermal Environment and Sleep Quality of Middle-Aged Residents in a Tropical Climate

Abstract

The field survey on indoor thermal environment was conducted in real-life 22 houses occupied by 29 middle-aged men and women in the suburbs of Kuala Lumpur, Malaysia. 18 had air conditioners (AC) in the master bedroom, and 4 had natural ventilation (NV), though all homes had ceiling or standing fans. During nighttime sleeping hours, the average air temperature (Ta) in the participants' bedrooms ranged from 22.6°C to 32.2°C, with relative humidity (Rh) varying between 32% and 80% and airflow between 0.1 and 1.3 m/s. Based on the ET* values, the participants were divided into three groups (A, 20.9°C–24.9°C ET*; B, 25.0°C–27.9°C ET*; and C, 28.0°C–32.5°C ET*), and sleep variables were then compared among the three groups. Group B had the shortest time to fall asleep, whereas group C had the longest awakening time during sleep. The sleep efficiency index (SEI) revealed that sleep quality in group C was inferior to that in group A. No differences were observed in subjective sleep sensations and thermal comfort among the groups, except for humidity sensation. This study demonstrates the importance of using activity meters to measure objective sleep variables in daily life.