Traffic-related air pollution and sleep: Variations by gender and socioeconomic status

Poor sleep and sleep apnea vary by sociodemographic factors, and are linked with adverse health outcomes. A number of risk factors are known, however little is known about environmental determinants. We investigated the association between black carbon (BC), a marker of traffic-related air pollution, and self-reported sleep duration, sleep latency (time to fall asleep) and sleep apnea risk (Berlin), and how associations vary by gender, race, SES, and health conditions (e.g., diabetes), in a large cohort of men and women who participated in the Boston Area Community Health Survey. Residential 24-hour BC level was estimated from a validated land-use regression model for 3,821 participants up to a year prior to participation and averaged. Linear and logistic regression models controlling for a priori selected confounders, estimated the association between sleep outcomes and BC. Effect modification was tested with interaction terms. Main effects were not observed for any outcome. However, in stratified models, sleep duration (hours) was inversely associated with BC (&mug/m3) in males (&beta=-1.06; 95%CI:-1.97,-0.14; interaction-p<0.01) and in low SES individuals (&beta=-1.17; 95%CI:-2.29,-0.06; interaction-p=0.04). Blacks however showed a positive association between sleep duration and BC (&beta=1.63; 95%CI:0.55,2.71), which persisted when further stratified by gender and SES. There were no significant interactions between BC and season or health conditions for any outcome. BC was not associated with risk of sleep apnea, however findings suggest traffic-related air pollution may be associated with sleep duration, particularly in men and those with low SES. The reasons why particular subgroups may be differentially affected are unclear.