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Sickness absence is widely used as health indicator in occupational health research. Although several studies investigated the effect of irregular working hours on sickness absence, the association remains unclear due to contradictory findings.
Apart from being involved in irregular working hours, flight crew have to deal with the crossing of time zones and the subsequent circadian disturbances. It has been shown that these conditions can cause fatigue, reduced sleep quantity, quality, and jet lag. Until now however, it remains unclear which aspects of work schedules of flight crew are related to sickness absence. The aim of this study is to determine which aspects determine sickness absence.
Methods
A five-year historic cohort was composed out of medical and human resource records of flight crew of a European airline company. In total, data from the period January 2005 to January 2010 of 8228 employees was included for analyses. The number of sickness absence days and number of absence spells during 2009 were the dependent variables. Independent variables were; the sum of night flights, sum of hours spent abroad, and the total of time zones crossed, calculated for the period 2005 until 2008. Linear regression techniques were used to analyze the data, including confounder correction.
Results
Work schedule aspects were significantly associated with both the amount of sickness absence days and number of absence spells. After adjusting for confounders (personal characteristics, contract size, and sickness absence during exposure), two of the three associations remained significant. For the night flights flown, and hours spent abroad, the found associations with sickness absence were b=-0.06 days [-0.11 -0.02] and b=-0.003 days [-0.007 0.001], respectively.
Discussion
Results revealed negative associations between several aspects of work schedules and sickness absence. However, because the found values were very small, it can be argued if these results are relevant.