Nocturnal road traffic noise and Sleep during Mid-Adulthood in Urban Settings: Examining Sex and Socioeconomic Differences within the DAS-EP Project.

Sleep is essential for physical and mental health but tends to deteriorate from mid adulthood, particularly among women. Nocturnal road traffic noise is a major environmental stressor that can disrupt sleep. This study aimed to examine the association between nocturnal road traffic noise and sleep health during mid-adulthood and explore potential sex-based differences. We conducted a cross sectional analysis using data from population health surveys (2021-2023) including 1,898 adults aged 40-60 living in urban areas of the Basque Autonomous Community, the Valencian Community, and Barcelona. Nocturnal road traffic noise was assessed using Lnight indicator, defined as the long-term average noise level during the night-time period (23:00-07:00), and estimated using official noise maps. Sleep health was assessed through self-reported measures of sleep duration, overall sleep satisfaction, and sleep quality using the SATED scale, a multidimensional measure of sleep health (Satisfaction, Alertness, Timing, Efficiency, and Duration). A Directed Acyclic Graph (DAG) was used to identify covariate adjustment sets and associations were estimated using linear models accounting for the complex survey design. Women generally reported poorer sleep health than men, with lower sleep satisfaction and poorer sleep quality, and sleep quality increased with area-level household income. Noise exposure increased with income at lower levels, while different patterns were observed across regions after €50,000. The association between noise exposure and sleep health varied across regions and sleep health dimensions. In Barcelona, higher noise exposure was associated with greater sleep satisfaction, but this association was not significant in pooled meta analyses. In contrast, higher noise exposure was associated with poorer sleep quality in the Basque Country, with the pooled meta-analysis showing a similar overall pattern. These findings highlight the context-dependent nature of noise-sleep relationships and support the need for targeted public health strategies.