Occupational noise exposure, social class, and risk of ischemic heart disease and all-cause mortality--a 16-year follow-up in the Copenhagen Male Study.

OBJECTIVE: Long-term exposure to occupational noise may be associated with an increased risk of ischemic heart disease (IHD) and all-cause mortality. However, the issue remains unsettled. Only a small number of longitudinal studies have been carried out, and control for potential confounders including a strong correlate of noise exposure namely social class may have been insufficient.
METHODS: We carried out a 16-year follow-up of 2998 men aged 53-75 years without overt cardiovascular disease. RESULT: Overall, 197 men (6.6%) died due to IHD and 1192 (39.8%) from all-causes. Of the 2998 men, 1008 (33.6%) reported exposure to occupational noise for ≥5 years [mean 25.4, standard deviation (SD) 12.5 years]; among these men, 47.3% reported hearing impairment versus only 24.8% among unexposed men (63.0%). Referencing unexposed men, the hazard ratio (HR) for IHD mortality was 0.97 [95% confidence interval (95% CI) 0.71-1.33], and the HR for all-cause mortality was 1.01 (95% CI 0.89-1.15) when adjusting for potential confounders: age, hearing impairment, blood pressure, diabetes, fasting serum triglycerides and high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, glucosuria, cancer, body mass index, alcohol, tobacco, leisure-time physical activity, and social class. Stratified analyses of high and low social classes confirmed the overall results.
CONCLUSION: Cumulative occupational exposure to noise was strongly associated with hearing impairment, but not with death from either IHD or all-cause mortality in a long-term follow-up adjusting for established cardiovascular risk factors including low social class.