Relationship between time-varying exposure to occupational noise and incident hypertension: A prospective cohort study

Background: Exposure to occupational noise might increase the risk of hypertension. However, limited cohort studies have investigated the relationship between time-varying exposure to occupational noise and the development of hypertension. Methods: We conducted a 17-year cohort study involving 2459 workers to assess the relationship between time-varying exposure to occupational noise and incident hypertension in the aerospace industry. We performed an extended Cox proportional hazard model considering occupational noise exposure as time-varying covariates. Furthermore, we employed the distributed lag nonlinear models (DLNMS) to examine the exposure-response relationship. Results: In the extended Cox proportional model, as workers were exposed to noise over 80 dBA, the hazard ratios (HRs) of hypertension significantly increased with a noise increase of 5 dBA (HR = 1.16, 95% CI: 1.04-1.29). In exposure-response associations, the HRs of hypertension steadily increased between noise levels of 82 and 106 dBA (HRs ranged from 1.04 to 1.46). After additionally adjusting for personal protection equipment (PPE), the HRs decreased dramatically between 107 and 124 dBA (HRs ranged from 1.45 to 1.00). Conclusions: Our study refined the exposure assessment by integrating time-varying exposures to occupational noise and taking work history into consideration. Our findings suggested that workers exposed to noise levels between 82 and 106 dBA for 3-17 years may increase the risk of hypertension with a non-linear exposure-response pattern. We further provided evidence that workers wearing PPE could effectively reduce noise exposure and avoid the development of hypertension.