. 2020 Sep 28;10(9):e039576. doi: 10.1136/bmjopen-2020-039576

Table 1.

Meta-analysis of typical cohort studies on NIHL incidence

Author	Type of factory	Population		Study duration	Years of follow-up	Noise level (max or mean)(dB(A))	NIHL incidence (%)
Author	Type of factory	N	Exposure duration (years)	Study duration	Years of follow-up	Noise level (max or mean)(dB(A))	HFNIHL	SFNIHL	Average
Jing⁵⁹	Oil field	673	1.0–30.0	2006–2010	5	106.8	30.6	3.7	17.2
Xu⁶⁰	Electrolytic aluminium	1929	1.0–30.0	2008–2012	5	87.1±2.2	16.6	10.9	13.8
He⁶¹	Automobile	397	8.8±8.7	2014–2016	3	101.3	34.3	2.3	18.3
Total	–	2999	8.8±8.7	2006–2016	–	98.4±7.2	22.1	8.1	15.1

dB(A), A-weighted decibels; HFNIHL, high-frequency noise-induced hearing loss; NIHL, noise-induced hearing loss; SFNIHL, speech-frequency noise-induced hearing loss.