A detailed analysis of risk factors for the development of sensorineural hearing loss (SNHL) was carried out in 199 forest workers. The hearing threshold of both ears at 4000 Hz was measured, and the effect of age, exposure to noise, blood pressure, presence of vibration induced white finger (VWF), tobacco smoking, plasma LDL-cholesterol concentration, and consumption of drugs were evaluated by multiple linear regression analysis. Aging was the major risk factor, followed by exposure to occupational noise and the presence of VWF. Plasma LDL-cholesterol concentration and the use of antihypertensive drugs also correlated significantly with SNHL. These main factors were able to explain about 28% of the SNHL variance. Additional factors in the analysis, including smoking, systolic and diastolic blood pressure, and consumption of salicylates did not significantly contribute to the genesis of SNHL.

A longitudinal study on vibration syndrome among professional forest workers was carried out in Finland from 1972 to 1990. In the course of the follow-up the weighted vibration acceleration of chain saws decreased from about 14 to 2 m/s2. The prevalence of vibration-induced white finger (VWF) decreased gradually from 40% to 5%. Numbness occurred mainly at night, and its prevalence decreased from 78% to 28%. During part of the follow-up period (1975-1990) the complaints of hand muscle weakness decreased from 19% to 9%. Disorders of the musculoskeletal system were considered to cause more disability than VWF. The decreased vibration acceleration and the lighter weight of chain saws were considered the main reasons for the decrease in the prevalence of vibration-induced symptoms.

The presence of carpal tunnel syndrome (CTS) in 125 forestry workers with exposure to vibration was examined clinically by electromyography and by determining vibration detection thresholds. Numbness of the hands was present in 43%, history of diminished hand muscle force in 15%, and Raynaud's phenomenon in 27%. The muscle weakness correlated significantly with motor nerve conduction velocity in the median nerve in both hands. In 25 forestry workers CTS was diagnosed. The condition was bilateral in 48%; otherwise it was more common on the right side. Fifteen patients were referred for surgery but because of spontaneous recovery or refusal by the patients only five underwent surgery; of these four improved. The motor conduction velocity of the ulnar nerve was decreased among patients with CTS supporting the idea that entrapment neuropathies in the hands may be due to tissue swelling caused by vibration at work. Total exposure time to vibration correlated with the decrease in motor conduction velocity in the ulnar nerve.Prolonged exposure to hand-arm vibration may cause peripheral neuropathy'2 with symptoms such as numbness and pain in the hands, nocturnal paresthesia, and muscle weakness.34 The vibration induced symptoms in the peripheral nerves may arise from vascular insufficiency of the minute nerve terminals,56 by damage to the non-specific myelin sheath,' by intraneural oedema leading to secondary nerve degeneration,7 or by isolated nerve damage due to entrapment.8

No abstract

The presence of carpal tunnel syndrome (CTS) in 125 forestry workers with exposure to vibration was examined clinically by electromyography and by determining vibration detection thresholds. Numbness of the hands was present in 43%, history of diminished hand muscle force in 15%, and Raynaud's phenomenon in 27%. The muscle weakness correlated significantly with motor nerve conduction velocity in the median nerve in both hands. In 25 forestry workers CTS was diagnosed. The condition was bilateral in 48%; otherwise it was more common on the right side. Fifteen patients were referred for surgery but because of spontaneous recovery or refusal by the patients only five underwent surgery; of these four improved. The motor conduction velocity of the ulnar nerve was decreased among patients with CTS supporting the idea that entrapment neuropathies in the hands may be due to tissue swelling caused by vibration at work. Total exposure time to vibration correlated with the decrease in motor conduction velocity in the ulnar nerve.Prolonged exposure to hand-arm vibration may cause peripheral neuropathy'2 with symptoms such as numbness and pain in the hands, nocturnal paresthesia, and muscle weakness.34 The vibration induced symptoms in the peripheral nerves may arise from vascular insufficiency of the minute nerve terminals,56 by damage to the non-specific myelin sheath,' by intraneural oedema leading to secondary nerve degeneration,7 or by isolated nerve damage due to entrapment.8