Epidemiological diagnosis of occupational fatigue in a fly-in fly-out operation of the mineral industry

OBJECTIVE: A prospective epidemiological study was conducted at a fly-in-fly-out mining operation in Australia to assess the dynamics of occupational fatigue and its potential risk factors. METHODS: Performance and perceived fatigue were measured at the start/finish of each 12-h shift throughout the 28-day roster (10 days day shift work on-site, 5 days rest off-site, 8 days night shift work on-site and 5 days rest off-site) using the Mackworth Clock Vigilance test and the Swedish Occupational Fatigue Inventory, respectively. Additionally, major predisposing/reinforcing factors of fatigue were measured including a detailed sleep diary (length/quality of sleep, wake patterns), a diary on alcohol consumption and a general health/fitness questionnaire. RESULTS: Of 55 production staff at the site 52 (95%) participated in the study. Significantly increased occupational fatigue was observed at concerning levels at the finish of night shifts 1-3 and from day shift 8 onwards. At the measured level, total hours of sleep (average 6.8 h per night) and number of standard drinks (average 1.5) were not significantly correlated with fatigue measurements. CONCLUSIONS: A disturbed diurnal rhythm at the beginning of night shift and a roster of more than eight consecutive days were identified as the primary contributing factors to occupational fatigue in this setting. The observed magnitude of effects suggests adverse implications for safety as the effects on performance were beyond what would be expected at blood alcohol concentrations of 0.05%. The results of this study have been used to generate highly specific strategies to reduce fatigue in the workplace.