The effects of combined exposure of solvents and noise on auditory function - A systematic review and meta-analysis.
Faatima Nakhooda, Benn Sartorius, Samantha M Govender
PMID 31170785WHAT IT FOUND
Workers exposed to both noise and solvents had more hearing loss than workers exposed to solvents alone.
The studies were cross-sectional, so this does not prove solvents caused the loss.
Key findings
01Workers exposed to both noise and solvents had significantly higher pooled odds of hearing loss than workers exposed to solvents only (OR 2.15, 95% CI 1.24 to 3.72, p=0.006).
02In 10 of 13 studies, hearing loss prevalence was significantly higher in the noise and solvent group than in other groups, with a pooled OR of 2.754.
03Auditory pathology was present in 43.3% of 1222 workers exposed to combined noise and solvents.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The included studies were cross-sectional, so they cannot establish that solvents caused hearing loss. Heterogeneity was high, so the pooled odds ratio may not consistently represent the included studies. Many studies did not have a solvent-only group because solvents often coincide with noise, making it difficult to separate the solvent effect from the noise effect. Some studies had small sample sizes and unmatched group numbers, limiting the strength of conclusions. Workers were not always restricted by age, and some were above 60 years, when age-related hearing loss is common. Several studies did not measure cumulative solvent dose, personal noise exposure, or confounders such as smoking.
The easy way to misread this
Do not conclude that solvents caused the hearing loss. The studies were cross-sectional and often did not measure cumulative exposure, personal noise levels, age effects, smoking, or a solvent-only comparison, so they cannot separate the effect of solvents from noise.