Validation of the new whole-body vibration evaluation methods on the basis of the data of the previous epidemiological study "whole-body vibration" (wbv), Project part A

Status:

completed 01/2009

Aims:

- Use of the extensive data from the WBV study on vibration exposure and on the medical evaluation of the spine, in order to compare and evaluate current methods of vibration assessment
- Examination of the significance of the force-related characteristic values of vibration assessed in project part B

Activities/Methods:

- Recalculation of the exposure data from the WBV study based on K-rated acceleration values with the aid of current evaluation methods
- Statistical analyses of the relationships between exposure data and medical data
- Statistical analysis of the correlation between force-related characteristic values of vibration, age and medical findings

Results:

Significant statistical correlations between the maximum exposure during work life (determined from the activity period with the highest exposure) and the diagnosis lumbar syndrome were shown for the complete sample of the WBV study (n = 388 exposed workers) and particularly for the 315 subjects without any lumbar disorders up to the start of exposure. Similar results appeared for the sub-diagnosis local lumbar syndrome, but they did not appear for the local radicular syndrome.

In a regression analysis, age turns out to be the strongest predictor of lumbar syndrome, but the maximum daily exposure A(8) also contributes significantly. Referring to a stepwise increase of 0.1 m/s², the risk rises by 15% (OR = 1.15; Cl95%: 1.06/1.24). Furthermore, the same regression model allows for a surprisingly accurate prediction of a lumbar syndrome due to the strain in the y-direction, if the assessment acceleration awy(8) is used as characteristic value (OR = 1.23; Cl95%: 1.09/1.40).

The significance of the threshold value and the length of exposure with regard to health hazards are also subjected to a regression analysis. By carrying out logistic regressions with each participant´s maximum daily exposure A(8) as a single predictor and the target variable lumbar syndrome, one can deduce hints for the best fitting threshold value of the daily exposure. The importance of the threshold criterion for estimating the degree of risk is also shown in calculating different cumulative doses of vibration exposure during work life. Basically, a clear increase in risk results with an increasing cumulated dosis of vibration exposure during working life.

The evaluation of the x-ray results shows mainly a strong influence of age with regard to the large number of observed degenerative changes of the lumbar spine. However, there is no convincing evidence for a relation between the different parameters of vibrational exposure and the x-ray diagnoses. The most important result has been that the disc height in the segment L5/S1 seems to depend on the vibration exposure (assessment acceleration awz(8)) with an OR of 1,17 (CI95%: 1,02/1,34).

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