Analyses of the relationship between work absenteeism and influenza in NorwayArchived

Estimating influenza-related sick leave in Norway: Was work absenteeism higher during the 2009 A(H1N1) pandemic compared to seasonal epidemics de Blasio BF, Xue Y, Iversen B,et al. Euro Surveill. 2012;17(33):pii=20246. This innovative study by the Public Health Institute in Norway documents the impact of influenza on work absenteeism using data firstly from a national registry of general practitioner authorised sick leave and secondly a national company Norway Post AS, with more than 14 000 employees, to explore sickness absence patterns from 2005/06 through 2009/10 in Norway.    The authors found that the number of GP-certified sick leaves with an influenza diagnoses was on average around 47 000 in the seasons from 2005/06 through 2008/09, representing a sick leave rate of 1 950 (range: 1 600–2 610) per 100 000 persons employed. In the pandemic season, over 84 000 GP-certified sick leaves with influenza were registered. Overall sick leave increased by 50% in the pandemic season with an increase of nearly 80% in influenza diagnosed sick leaves compared with the mean level in the previous seasons.

The total number of working days at Norway Post AS, i.e. the number of person-days after deduction of leaves (except sick leaves) and holidays, declined by 15% from 3.41 million in the 2005/06 season to 2.91 million in the 2009/10 season. In the study period of the pandemic, self-certified and GP-certified work loss comprised 1.3% and 8.0%, respectively, of the total working days in the company. The overall work absence to care for sick children comprised 0.27% of potential working days, and the figure was comparable among women (0.26%) and men (0.29%). Overall, the work absence rate rose by a factor of 1.4 in the pandemic season, from around 10 300 (95% CI: 4 340–24 300) working days lost in the 2008/09 season to 14 750 (95% CI: 6 050–26 950) working days lost in the 2009/10 season. In the pandemic season, self-certified work absence accounted for 25% of influenza-associated work loss, while 65% was GP–certified, and 10% was related to sick children. The corresponding figures for the 2008/09 season were 36%, 61% and 3%, respectively. The authors estimated from the national database that, annually, on average 2.9% (mean 95% confidence interval (CI): 2.4% - 4.8%) of the working population obtained sick leave for influenza, of whom 0.9% (mean 95% CI: 0.5%-1.5%) had diagnoses for other respiratory illnesses but with influenza as underlying cause. In the 2009/10 pandemic season the absence rate increased 1.5-fold, mainly due to a 73% increase in influenza-diagnosed sick leaves.   At Norway Post AS, absence related to seasonal influenza accounted for 0.351% (mean 95% CI: 0.126–0.704%) of total person-days annually (excluding parental care absence), of which 32–43% were estimated to be self-certified. Medically certified sick leave increased 1.3-fold in the pandemic season to 0.458% (95% CI: 0.176–0.856), while self-certified sick leave remained at a level typical for seasonal influenza. There was a statistically significant four-fold increase in work loss to care for sick children, 0.048% (95% CI: 0.031–0.070%) of person-days, compared with 0.012% (95% CI: 0.004–0.028%) in 2008/09. The authors concluded that both GP-certified and parental care work absence were higher in the pandemic season.

ECDC Comment (9 October 2012):

This piece of work shows both that influenza is of economic consequence in being associated with workplace absenteeism and how innovative use can be made of workplace statistics, especially with large national employers such as Norway Post AS. Indeed it is surprising that more use of such information and data is not made routinely in other countries. Some use has been made of detecting outbreaks.[1] However the only other example of this known to ECDC is monitoring of absenteeism through a large national employer in Australia that took place during the 2009 pandemic.