Meta-analysis of Occupational Factors Contributing to Variability in Noise-induced Hearing Loss Severity

This meta-analysis aimed to systematically evaluate occupational factors that contribute to variability in noise-induced hearing loss (NIHL) severity across different industrial sectors and identify high-risk occupational groups for targeted intervention strategies. A comprehensive systematic review was conducted using MEDLINE, PubMed, Embase, Web of Science, and Google Scholar databases from January 2003 to January 2025. Studies were included if they reported quantitative measures of NIHL prevalence, odds ratios, or prevalence ratios (PRs) with 95% confidence intervals across different occupational sectors. Keywords included "noise-induced hearing loss," "occupational hearing loss," "prevalence," "odds ratio (OR)," and specific occupation terms including "miners," "construction workers," "manufacturing workers," "industrial noise," "deafness," and "occupational disease." Data extraction focused on study characteristics, participant demographics, noise exposure levels, and NIHL outcomes. Random-effects meta-analysis models were employed using Stata 17.0 (StataCorp LLC, College Station, TX, USA). Forest plots were generated using Review Manager 5.4 (The Cochrane Collaboration, Copenhagen, Denmark). Eleven cross-sectional studies (no cohort or case-control studies met the inclusion criteria) encompassing 169,804 workers across multiple industries were included. Mining demonstrated the highest NIHL severity, with prevalence ranging from 22.9% to 47%. Gold ore mining showed a prevalence of 22.9%, while support activities for coal mining exhibited a prevalence of 18.1% with risk elevation. Manufacturing sectors showed consistent risk elevations across geographic regions, with developing countries reporting higher prevalence rates (20.4%-30.7%) compared to developed countries (14%-17%). Construction industry workers had prevalence rates of 17% to 26.9% across different subsectors. Age emerged as a critical modifier, with workers ≥35 years showing substantially increased risk. Geographic variations were observed, with developing countries generally reporting higher prevalence rates across all industries. Mining demonstrates the highest NIHL risk (PR up to 2.02), followed by construction and manufacturing. These findings support industry-specific hearing conservation programs in high-risk occupational environments.