Till Örebro universitet

Hand-arm vibration (HAV) is a common occupational exposure in Sweden and worldwide that causes both acute transient effects and persistent hand-arm symptoms. The health effects include vibration-induced Raynaud’s phenomenon, neuropathic symptoms, carpal tunnel syndrome (CTS), and musculoskeletal disorders. The overall aim of this thesis was to investigate vascular and neurological effects in the hands of workers exposed to hand-arm vibrations.

Methods: In study 1, the aim was to investigate the risk of CTS from hand-arm vibration. This study was conducted as a register study using the National Outpatient Register and a job exposure matrix to estimate HAV exposure. Study 2 aimed to investigate the acute effects of HAV on the nerve functions of the hands and the impact of grip force. Nerve function was evaluated before and after vibration exposure. In study 3, the aim was to identify low molecular organic biomarkers in blood samples from vibration-exposed workers using a novel metabolomics approach. HAV-exposed workers underwent medical examination and blood samples were collected and analysed before and after a work shift. In study 4, the aim was to investigate if arterial abnormalities in the hands could be identified in patients with VWF which also had a positive Allen’s test. In this case series, Doppler ultrasound and magnetic resonance angiography (MRA) investigations were performed to investigate the arterial status in the hands. 

Results: Study 1 showed that the risk of CTS for HAV exposed individuals increased with an OR of 1.61 (95% CI 1.46-1.77) for the whole population. The risk was highest in HAV exposed younger males. Study 2 showed that HAV exposure with high grip force affect nerve function different than with low grip force. In study 3, workers with VWF had metabolic profiles different from participants without VWF, both before and after vibration exposure. In study 4, ultrasound and MRA identified vascular abnormalities in all participants; these abnormalities were a predominantly missing or not complete superficial arch. 

Conclusion: The overall finding is that HAV exposure, even at levels under legislated values, can give negative health effects. These results add new knowledge about CTS, HAV exposure and gender. Both metabolomics and studies of acute effects of HAV could be further studied to find a level of exposure where no health effects appear. With the findings on MRA, there is the possibility that a subgroup of VWF can be subject for treatment.