The JADE study used the same methodology as that described by Bates et al in 19954
. The incidence of ADEs in the present study was 17.0 per 1,000 patient-days, which was fairly similar to the 11.5 that reported by Bates et al. However, the rate per admission differed substantially between the present study and that of 1995 Bates study--29 vs. 6 ADEs per 100 admissions. This gap was primarily due to the large difference in the mean length of hospital stay between Japan and the U.S., which was 17 vs. 5 days, respectively. However, our results were consistent with another recent epidemiological report on inpatients from the U.S. which found an incidence of 15 ADEs per 100 admissions14
. Hospitals can be dangerous places, and shortening stays in Japanese hospitals could potentially reduce the frequency of ADEs. The reasons for the differences in length of stay are largely cultural and relate in part to patient expectations15,16
. Physicians and even patients, can determine the timing of discharge more freely in Japan compared to the U.S16,17
. In addition, the reimbursement from government-run health insurance is generally based on the length of hospital stay, and because of shortages of ambulatory care, the physicians, patients, and their families are all inclined to keep patients in hospital longer17
. Thus, the findings that longer hospital stay is substantially associated with ADEs represents one incentive to shorten the length of hospital stay, though many factors are clearly involved.
We found many common epidemiological characteristics of ADEs and medication errors between Japan and the U.S., including the severity and drug class of ADEs, ward type, stage of medication errors, and proportion of interception of potential ADEs. For example, nearly half of all medication errors occurred at the ordering stage (66% in Japan and 49% in the U.S.), followed by the administration or monitoring stages. Both studies also found that almost half of potential ADEs were intercepted before the drugs reached patients. These findings support the notion that ADEs and medication errors may represent similar processes despite major differences in medical systems and cultures, although the situation might also be quite different especially in settings such as developing countries.
We assessed the frequency of ADEs and medication errors in daily practice in hospitals in Japan and found that they occur often and cause substantial harm. Based on these data, healthcare professionals, policy makers, patients, and even the general population should be aware of the risk of medical care and drugs. Because the epidemiology and characteristics of ADEs and medication errors were quite similar despite differences in healthcare systems, extrapolation from state-of-art solutions in the U.S. such as computerized physician order entry, bar-coding, and having pharmacists round with teams in the intensive care units should be evaluated in Japan and perhaps other developed countries, with public support and investment18,19
In addition, we identified several specific factors that were associated with ADEs in Japan. Older patients, those in ICUs, those transferred from other wards, and those with a history of allergy as well as those cared for by resident physicians were all at higher risk for ADEs. Thus, solutions targeting these groups could be especially effective locally in Japan. Transition from other wards was considered a particularly high risk for any kind of harm from medical care and a top priority of patient safety in developed countries13
. Although regulating work hours in the U.S. does not apparently reduce ADEs20
, other interventions for workplace and education for resident physicians could also be a focus of research.
Our study has several limitations. First, we analyzed data generated by the random sampling of wards from only three urban tertiary care hospitals. Therefore, our results might not be representative of Japanese inpatients in general. Also, healthcare providers might have been aware of this prospective cohort study, but a Hawthorne effect if present would suggest that our estimates are if anything conservative. Similarly, some ADEs may not have been noted in the charts and may thus have been missed, which would also make our estimates a lower bound. In addition, data collection was conducted in 2004, so that the current situation might be different. The main outcomes of our study were ADEs and medication errors, which required implicit judgment. However, the interrater reliability levels were reasonable and more robust alternatives to measure ADEs and medication errors have not yet been developed1
, so that the approach we used is the standard one.
In conclusion, we showed that ADEs and medication errors were quite frequent in Japanese acute care hospitals, and that they were of a similar nature to those arising in the Western countries. The proportion of preventable ADEs and of potential ADEs with medication errors among all incidents was significant, and most of the errors occurred at the ordering, administration and monitoring stages. Interventions to support healthcare providers during ordering and administering to patients may improve drug safety among hospital inpatients, as could reducing length of stay. Future studies should assess the epidemiology in other settings in other countries, and the effectiveness of interventions that have been successful in the Western countries, such as the updating of information technologies, should be tested in other nations.