Prevalence of psychological distress and its association with perceived indoor environmental quality and workplace factors in under and aboveground workplaces

The development of underground spaces serves a range of common urban functions, including workspaces. However, underground workplaces, work-related factors and the indoor environmental quality (IEQ) parameters within them may negatively affect worker's mental health. This study assessed the prevalence of psychological distress with repeated measures over time in aboveground and underground workspaces, and assessed the association between perceived IEQ parameters and work-related factors with psychological distress. A total of 329 workers in similar aboveground and underground workspaces were followed-up in three assessments over 12 months in Singapore. Psychological distress was assessed using the 12-item General Health Questionnaire (GHQ-12) and defined as a GHQ-12 score >2. Perceived IEQ (air quality, temperature, noise, light) in the workplace were collected using the OFFICAIR questionnaire. We used generalised estimating equation models to assess the association between working underground, perceived IEQ, and work-related factors with psychological distress. The overall prevalence of psychological distress was 21.9%, 26.1% and 21.9%, at baseline, 3- and 12-months follow-up, respectively. The fully-adjusted multivariable analysis did not show any association between working underground and psychological distress, however, perceived IEQ parameters and longer working hours were significantly associated with psychological distress. Regardless of working in under or aboveground workplaces, perceived IEQ was associated with psychological distress. Future studies are needed in order to examine the relationship between objective measures of IEQ and psychological distress and the impact of healthy building policies and improved IEQ on psychological distress.