Objectives To assess whether, compared with previous years, hospital care became safer in 2011/2012, expressing itself in a fall in preventable adverse event (AE) rates alongside patient safety initiatives.

Design Retrospective patient record review at three points in time.

Setting In three national AE studies, patient records of 2004, 2008 and 2011/2012 were reviewed in, respectively, 21 hospitals in 2004, 20 hospitals in 2008 and 20 hospitals in 2011/2012. In each hospital, 400, 200 and 200 patient records were sampled, respectively.

Participants In total, 15 997 patient admissions were included in the study, 7926 patient admissions from 2004, 4023 from 2008 and 4048 from 2011/2012.

Interventions The main patient safety initiatives in hospital care at a national level between 2004 and 2012 have been small as well as large-scale multifaceted programmes.

Main outcome measures Rates of both AEs and preventable AEs.

Results Uncorrected crude overall AE rates showed no change in 2011/2012 in comparison with 2008, whereas preventable AE rates showed a reduction of 45%. After multilevel corrections, the decrease in preventable AE rate in 2011/2012 was still clearly visible with a decrease of 30% in comparison to 2008 (p=0.10). In 2011/2012, fewer preventable AEs were found in older age groups, or related to the surgical process, in comparison with 2008.

Conclusions Our study shows some improvements in preventable AEs in the areas that were addressed during the comprehensive national safety programme. There are signs that such a programme has a positive impact on patient safety.