Risk of death from motor-vehicle injury in Brazilian steelworkers: a nested case-control study

In a cohort of 21,816 Brazilian steelworkers we found mortality from motor-vehicle injury was twice that in the State population. A nested case-control study was therefore undertaken to investigate possible socio-demographic, medical and occupational risk factors for this increased risk.

Cases were defined as all steelworkers in the cohort who died of motor-vehicle injury during employment in the period 1977-1992. For each case, four controls were selected at random from workers in the cohort who were employed at the time of death of the case, and who were born in the same year as the case. Data on socio-demographic factors, and medical and occupational histories were obtained from personnel, industrial hygiene and medical records, and the relation of these factors to risk of motor-vehicle injury was analysed using conditional logistic regression.

In a multivariate analysis, the risk of death from motor-vehicle injury was independently associated with being unmarried (odds ratio [OR] compared to married = 3.21, 95% confidence interval [CI]: 1.84-5.59), having a hearing defect (OR = 2.28, 95% CI: 1.10-4.74) and exposure to moderate (OR = 1.71, 95% CI: 1.03-2.83) or high (OR = 2.00, 95% CI: 1.18-3.39) levels of noise at work. The risk of fatal motor-vehicle injury increased with intensity of occupational noise exposure (P = 0.004).

The raised risk of motor-vehicle injury death associated with single marital status is likely to relate to selective factors in the types of individual who remain single, and behaviours associated with being unmarried. The raised risks in relation to hearing defects and exposure to occupational noise, factors that do not appear to have been examined previously, imply that occupational noise exposures might be a cause of fatal motor-vehicle accidents outside the workplace. This finding may have widespread public health consequences since high levels of noise in the workplace and occupationally acquired hearing deficits are prevalent in several occupations. Further investigation is needed to confirm the associated and its mechanisms and, if it is causal, to develop preventive strategies.