Military aircraft noise and drug administrations in psychiatric patients: Follow-up and in-depth case-time series analysis

Background: In a previous study, we demonstrated that military aircraft noise increases the short-term probability of on-demand drug administrations in patients in a psychiatric clinic located in close proximity to a military airfield. The aim of this article was to: (1) apply refined exposure assessment methods; (2) compare results for various noise exposure measures reflecting different assumptions about outdoor–indoor noise attenuation and explore possible effect thresholds; and (3) conduct an independent validation study with 1 year of more recent follow-up. Methods: We conducted noise measurements during 1 year at the clinic to validate the modeled noise exposure of hourly military aircraft noise (equivalent continuous sound pressure level, LAeq [dB]). We then compared results from case-time series analyses between on-demand drug administration and military aircraft noise using modeled versus measured aircraft noise exposure, different censoring approaches for background noise, and explored a potential threshold using nonlinear exposure–response modeling. Results: There was a moderate (Pearson’s r = 0.54) to strong (r = 0.65) correlation between modeled and measured aircraft noise levels, depending on the wind situation. Applying censoring at levels reflecting background noise in the range of 40–50 dB instead of censoring exposure at 20 dB resulted in higher effect estimates, but also larger uncertainty compared with the previous analysis (original analysis, censoring at 20 dB: odds ratio [OR] for sedative administration = 1.016 per 10 dB; realistic background analysis: OR = 1.036, 95% confidence interval [CI]: 0.994, 1.079). Additionally, we found indications of a nonlinear exposure–response relationship. Using measured instead of modeled aircraft noise exposure resulted in smaller effect estimates (modeled OR = 1.056, 95% CI: 0.970, 1.149; measured: 1.038, 95% CI: 0.983, 1.096). Analyses exclusively using new data from the year 2022 revealed almost identical results compared with the original analysis (2016–2021). Conclusion: Our results suggest that predicting indoor noise levels and the addition of informed background noise estimates improves specificity in the exposure assessment and likely provides more reliable exposure–response associations. With additional follow-up data, we could confirm our previous findings that loud noise events can have acute effects on psychiatric patients’ sedative drug consumption.