The mediating role of sleep in the association between environmental noise and mental health

Exposure to environmental noise in residential areas has been associated with adverse mental health outcomes; however, the mechanisms of this relationship remain underexplored. This study investigates the contribution of reduced sleep quality to the negative association between perceived neighbourhood environmental noise exposure and poor mental health. We used the Household Income and Labour Dynamics in Australia (HILDA) survey and applied causal mediation methods to examine the role of sleep in the association between self-reported exposure to road traffic noise and plane, train and industry (PTI) noise and mental wellbeing at three time points between 2012 and 2021. Road traffic noise was associated with poorer mental health in 2012-13 and 2016-17, while no evidence of an association was observed in 2020-2021 (the period of COVID-related lockdowns in Australia). For the years where a significant association was observed, mediation analyses suggest that reduced sleep quality accounts for 21% (in 2012-13; 95% CI: 7-35%) and 33% (in 2016-17; 95% CI: 26-64%) of the total effect of perceived traffic noise on mental health. Perceived PTI noise was associated with poorer mental health in 2016-2017 and 2020-2021, with mediation through sleep observed in 2016-2017 (proportion mediated 20% (95% CI:3-38%)). Mediation by sleep quality was stronger among people reporting exposure to multiple noise sources than among people reporting exposure to a single noise source. As much as a third of the association between road traffic noise and poor mental wellbeing may be due to poorer sleep quality following exposure to unwanted noise.