Increased use of anti-bacterials is associated with anti-bacterial resistance. In Norway, the total use of anti-bacterials is on the rise. Most of the anti-bacterials are prescribed by general practicians (GPs), mainly for respiratory tract infections (RTIs).
Based on data collected from GPs in Norway, we explored the hypothesis that there is an increased likelihood of getting an anti-bacterial for RTIs on Fridays; that there is an increased likelihood of getting broader-spectrum anti-bacterials on Fridays; finally, that certain subgroups of patients or GPs, are more associated with Friday effects than others. Multivariate logistic regression analysis was performed. Factors that have proven to affect the odds of getting an anti-bacterial in the same data material in a previous report were included to avoid confounding.
There was less than 10 percent variation across the days of the week in the odds of getting an anti-bacterial for RTIs. Friday s odds were not statistically different from the odds of Monday through Wednesday, but about 10 percent higher than Thursday s looking at the entire data material. Mondays had the highest odds looking at GPs with an even workload-distribution through the week. The week did not affect the likelihood of getting broader-spectrum anti-bacterials. There were no convincing Friday effects associated with specific age-groups of patients, or with specific subgroups of GPs.
The day of the week is a weak predictor of getting an anti-bacterial for RTIs. In particular, we found no convincing Friday effect. Instead, there is a tendency that Mondays carry the highest odds looking at GPs with even workload-distribution through that week. This could suggest that the odds of getting an anti-bacterial increases with the length of the illness.