An association between Raynaud's phenomenon and hearing loss in forestry workers

Forestry workers using chain saws run the risk of both vibration disease and noise-induced hearing loss. It was reported that people with Raynaud's phenomenon of occupational origin had more severe hearing loss than those without it. A possibility of confounding due to age and duration of noise exposure from the tools remained unsolved, however. A matched pair case-control study was conducted to eliminate such confounding. Forestry workers operating chain saws, bush cleaners and/or winches were investigated. For 37 men with Raynaud's phenomenon a control was chosen from those unaffected whose age and operating hours for the tools were almost equal to those of the cases. Good matching was achieved for age and for total hours of work with the tools. The cases had higher median hearing threshold than the controls at every frequency. The difference was significant (p less than 0.05) at 4 and 8 kHz and almost significant at 2 kHz (p not equal to 0.06). According to our classification of the audiogram, the cases had more advanced types of noise-induced hearing loss than did the controls. Thus, an association between Raynaud's phenomenon and hearing impairment in forestry workers handling chain saws and/or other tools was found to persist even after the effect of age and exposure time was eliminated.