Trends in adverse events over time: why are we not improving?

With widespread interest and investments in patient safety in the 13 years following the US Institute of Medicine report To Err is Human,1 the question has under-standably arisen: have we decreased medical harm? One widely cited study showed no significant reductions in either the overall rate of harm or the rate of preventable harm in 10 US hospitals chosen on the basis of patient safety activities.2 A second US study,3 though not focused on temporal trends, reported that one third of patients suffered harm from their medical care at three tertiary care hospitals recognised for their efforts in improving patient safety. Given that previous major studies reported adverse event rates in the range of 3–16%,4–10 progress seems sorely lacking. Adding to this distressing picture, Baines et al11 report in this issue of the journal that the adverse event rate among hospitalised patients in the Netherlands increased from 4.1 % in 2004 to 6.2 % in 2008. Somewhat reassuringly, preventable adverse rate did not change. The increase in non-preventable adverse rates may reflect better documentation in medical records as a result of interest in patient safety, with the stable rate of preventable events suggesting that safety has not actu-ally worsened. Nonetheless, the main message of this study11 and the two pre-vious ones2 3 remains: sustained attention to patient safety has failed to produce widespread reductions in rates of harm medical care.