Aircraft noise exposure and saliva cortisol in the DEBATS longitudinal study

Abstract

IntroductionAlthough aircraft noise is known to impact human health, the biological pathway is still unclear. One of the possible pathway is that aircraft noise exposure may induce a modification of the cortisol circadian rhythm. However, only a few studies have examined the association between this exposure and cortisol levels.ObjectivesThis longitudinal study conducted in France aimed to investigate the association between aircraft noise exposure and saliva cortisol levels.MethodsThe DEBATS study included 1,244 participants living near three French major airports. In 2013, 2015 and 2017, these participants responded to a face-to-face questionnaire administered at their home by a trained interviewer and collected two saliva samples: the first one immediately after awakening (when the cortisol level is usually high) and the second one just before going to bed (when the cortisol level is usually the lowest). ELISA kits were used to determine morning and evening cortisol levels in saliva for the 1,115 participants who followed the protocol and did not use any medication that could modify cortisol levels. Outdoor aircraft noise levels were estimated at each home address using noise maps. To estimate the associations between noise levels and cortisol levels (morning, evening, relative daily variation), linear mixed models were used with a subject-specific random intercept and adjusted on potential confounders.ResultsA 10 dB(A) increase in the day-evening-night (Lden) level was associated with decreased relative daily variation of cortisol (exp(β)=0.77; 95% confidence interval: 0.70-0.85), higher evening cortisol levels (exp(β)=1.16; 95% CI: 1.08-1.23) and unchanged morning levels (exp(β)=0.95; 95% CI: 0.90-1.00).DiscussionThe results of this study support the hypothesis that aircraft noise exposure was associated with flattened diurnal cortisol rhythm across the day, indicating a possibly disturbed hypothalamus-pituitary-adrenal axis regulation.