title: [Cox regression model of hearing loss in workers exposed to noise and metalworking fluids or welding fumes].
abstract: BACKGROUND
  Works on labour-related hearing loss have traditionally been centred on the study of noise as the principal cause. The presence of physical and chemical pollutants is very common in the metalworking branch. This article analyses both, together with certain personal habits, with the aim of determining their joint influence on labour-related hearing loss.
  
  
  METHODS
  A sample of 558 workers was analysed using Cox regression with an explicative aim. The character of the cause-effect relations existing between the variables considered is defined with respect to three situations: healthy/altered; recoverable/non-recoverable; with falls in conversational abilities/without falls in conversational abilities.
  
  
  RESULTS
  The analysis reflects the fact that metalworking fluids, in the presence of noise, delay the acquisition of different degrees of auditory alteration; an effect contrary to that produced by welding fumes, which accelerate such states. The habit of smoking is recognised as having an influence on the acquisition of an initial acoustic trauma; exposure to noise outside the workplace influences the acquisition of an advanced acoustic trauma; and, on the other hand, the auditory protective equipment provides protection against noise.
  
  
  CONCLUSIONS
  The antagonistic effect of metalworking fluids and the synergic effect of welding fumes in the face of noise are made evident in relation to these environments, explaining the temporal variation in the evolution of auditory alteration; the influence of tobacco and noise outside the workplace in the acquisition of acoustic trauma are confirmed.
authors.affiliation: Departamento de Microbiología, Medicina Preventiva y Salud Pública, Universidad de Zaragoza, Spain. jcconte@unizar.es
authors.forename: J C Conte
authors.initials: JC
authors.lastname: Solano
authors.forename: A I Domínguez
authors.initials: AI
authors.lastname: Gracia
authors.forename: A I García
authors.initials: AI
authors.lastname: Felipe
authors.forename: E Rubio
authors.initials: ER
authors.lastname: Calvo
authors.forename: A Pérez
authors.initials: AP
authors.lastname: Prados
mesh_terms: D034381:Hearing Loss / Q000139:chemically induced / Q000453:epidemiology* / Q000209:etiology*; D006317:Hearing Loss, Noise-Induced / Q000453:epidemiology; D006801:Humans; D009623:Noise, Occupational / Q000009:adverse effects*; D009784:Occupational Diseases / Q000453:epidemiology* / Q000209:etiology*; D016273:Occupational Exposure / Q000009:adverse effects*; D016016:Proportional Hazards Models; D012044:Regression Analysis; D014896:Welding