[Fatigue and workability in twelve-hour fixed shifts]

To analyze the variables associated with fatigue perception and workability on workers working 12-hour fixed night and day shifts.

A cross-sectional study was carried out. Forty-three workers, working 12-hour fixednight and day shifts in a textile factory, filled out questionnaires about fatigue, workability index, individual characteristics, life style and working conditions. A univariate linear regression analysis was performed.

Fatigue-related factors are associated to the workers' life style (physical activities is a protection factor), and sleep difficulties, with may increase fatigue perception. Workability-related factors are associated to longevity on job and working night shifts - workability index decreases as job longevity increases. Working night shifts showed a higher workability index. The 12-hour shifts may cause a considerably higher workload, influencing worker's perception of fatigue and workability index and sleep disturbances.

The results indicate that night shifts may not always be translated a health problem. However, this was a cross-sectional study with a small population sample and selection bias is not excluded. Since the workability index reduces while job longevity increases, there is a need for further longitudinal studies with larger population samples.