The role of depressive symptoms within the association of long-term exposure to indoor and outdoor traffic noise and cognitive function - Results from the Heinz Nixdorf Recall study.

Objectives: Traffic noise is negatively associated with cognitive function, and its perception can differ between depressed and non-depressed people. We studied the role of depressive symptoms in the association between traffic noise and cognitive function. We studied the role of depressive symptoms in the association between traffic noise and cognitive function.

Methods: During the first follow-up examination (2006-2008) of the German Heinz Nixdorf Recall study, cognitive function (five subtests and an additive global summary score, GCS) and depressive symptoms (CES-D score) were assessed in 2745 participants (aged 50-80, 49.8% women). Mild cognitive impairment (MCI) was diagnosed according to the Petersen criteria in 380 participants. Long-term exposure to traffic noise was modeled as weighted 24-h mean (L) and night-time mean (L) at the façade of the baseline addresses, and was corrected for indoors (L and L). We developed multiple linear and logistic regression models adjusted for individual-level characteristics to investigate cross-sectionally the role of depressive symptoms in the association of traffic noise with cognitive function.

Results: Overall, 8.6% participants had depressive symptoms. The median noise values were L 52.1 dB(A) and L 34.7 dB(A). Associations were slightly stronger for cognitive subtests in those with severe depression (CES-D>21), i.e., per 10 dB(A) L and verbal fluency: β = -0.04 [-0.11; 0.03] for CES-D≤21 and β = -0.09 [-0.24; -0.06] for CES-D>21. Additional adjustment of the main model for CES-D did not change the association between noise and cognitive outcomes. Estimates using indoor noise exposure were generally stronger and more precise.

Conclusions: Depressed people may be more susceptible to adverse effects of noise than non-depressed. Modeled estimates of indoor noise exposure is possibly a more appropriate measure of exposure.