Ambispective cohort study of noise-induced hearing loss among occupationally noise-exposed workers in a city

  Objective  To understand the incidence and potential affecting factors of noise induced hearing loss (NIHL) among occupationally noise -exposed workers in a city.

  Methods  Totally 3 580 workers exposed to noise, who received occupational health examination during January 1, 2010 to December 31, 2016 in 20 enterprises, were selected by the cluster random sampling method to establish a cohort. The cohort was followed till the end of December 31, 2019, with retrospective collection of previous physical examination data before 2016. The Cox proportional risk model was used to study the influencing factors of noise induced hearing loss of workers.

  Results  Among 3 580 workers, 2 849 were male and 731 were female with average age of (39.42±7.69)years and average service time of (11.50±7.06)years. The total follow -up time was 28 585.65 person years, and 91 cases had noise induced hearing loss with incidence density of 0.003 2/person year. With the increase of noise exposure level, the incidence density, relative risk (RR)and attributable risk percentage (AR%)of NIHL of workers also increased. Regression analysis of Cox proportional risk model showed that the risk of NIHL in women was 0.148 times higher than that in men; the risk of NIHL of workers who used appropriate protective equipment all the time was 0.407 times that of those who did not use; the risk of NIHL increased to 1.074 times with one year increment of age, and the risk of NIHL of workers with shifts was 2.588 times that of workers with regular day-shift; the risk of NIHL of smoking workers was 1.092 times that of non-smoking workers; the risk of NIHL of workers exposed to noise of sound level more than 85 dB (A)was 4.272 - 25.430 times that of workers exposed to noise with sound level lower than 8 5 dB (A)(P < 0.05).

  Conclusions  Higher noise exposure level was a risk factor of NIHL. It is necessary to strengthen the supervision of enterprises exposed to high-level noise, and pay attention to the wearing of protective equipment for workers in enterprises.