Participants and Setting
The study was conducted on patients aged 20 years or older who consulted Minamihama clinic, general outpatient department in July 2016 for regular drug prescriptions. Minamihama clinic is in a city that is approximately 20 minutes from Tokyo, with a population of roughly 600,000. The clinic is run by five doctors and provides primary care services, including outpatient consultations, dialysis, and home visits.
In an awareness survey on polypharmacy, the participants answered a self-administered questionnaire during their regular visits at the clinic. The questionnaire was given to all eligible patients in the study period. Eligible patients received a questionnaire from the medical office at the reception desk and completed it while waiting. After filling it out, they submitted it to the collection box. Questionnaires were given to consecutive patients.
The exclusion criteria were: patients who were under 20 years of age, institutionalized, or receiving care via specialized outpatient consultations, dialysis, or in-home visits. In addition, we considered questionnaires incomplete and excluded them if respondents had failed to answer one or more of their items.
There were 7 questionnaire items (supplementary 1). The questions asked: the patient's age, gender, number of medical institutions regularly consulted, whether the patient felt a need for prescription drugs, whether they understood the reason for the prescriptions, whether deprescribing medications made them anxious, and whether the patient had difficulty with asking their physicians to deprescribe their medications. All questions, except those about age, gender, and the number of medical institutions regularly consulted, had two answer options, "yes" or "no." If patients answered yes to whether they felt a need for prescription drugs, it was interpreted that all drugs are necessary, and if patients answered yes to whether they understood the reason for the prescriptions, it was interpreted that patients understood the reason for taking all drugs. We determined the survey items based on focus group discussions and the previously validated Patients' Attitudes Towards Deprescribing (PATD) questionnaire, which gauges how patients feel about their prescription drugs  (Y.H, K.S, Y.O, S.M, M.C, T.H). The questionnaire used in our study was developed for this study.
We followed an observational study design, and we conducted it in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. In Japan, taking 6 or more oral medications has been reported to increase the frequency of adverse drug events . In our study, polypharmacy was defined as taking 6 or more oral medications. Therefore, patients taking 6 or more oral medications were assigned to a polypharmacy group, and those taking 5 or less oral medications were assigned to a non-polypharmacy group. The number of oral medications taken by each patient was confirmed by a researcher (YH) who used electronic health records. We performed univariate and binomial logistic regression analyses, using a t-test and a chi-square test, to examine factors contributing to polypharmacy. The statistical power was set to 80%, the level of significance was set to 0.05, and a sample size of 134 people was necessary to demonstrate a significant difference.
All analyses were performed using the SPSS Statistics for Windows 26.0 software package (IBM, Armonk, USA).
Participants and Setting
The study was conducted among patients aged 20 years or older who regularly visited the Minamihama clinic during one month prior to and one month after we sent feedback to health professionals in August 2016. There were no staff changes during the above-mentioned periods.
We provided feedback to all 12 healthcare professionals (5 doctors, 4 nurses, 2 pharmacists, and 1 social worker) working at the clinic. For 15 minutes, we disclosed the results of the questionnaire survey from Study 1. Feedback was given face-to-face as a group.
Immediately after providing the results, we presented the 12 health professionals with 3 questions. We asked them: were the survey results useful for understanding the current state of polypharmacy patients, would there be changes in the medical care they provided now that they knew the survey results; and were the survey results unexpected (Table 1). For those who responded "Yes" to the question, "Were the survey results unexpected?", the health professionals' answer "more than expected," "as expected," or "less than expected." as the next item. Items were the results obtained from Study1 regarding percentage of polypharmacy, and the questionnaire items ("Do you feel that prescriptions are necessary?", "Do you understand the reason for prescription?", "Do you have anxiety about reducing medicine?", and "Do you feel difficulty talking about reducing medicine?") (Table 1).
Outcome and Measures
As primary outcomes, the number of polypharmacy patients and the number of prescribed medications were measured in adult patients who visited Minamihama clinic regularly during a one-month period before and after we gave feedback (April and October 2016). To determine the number of prescribed medications, medical receipt data was surveyed, and participants taking 6 or more oral medications were considered polypharmacy patients.
We followed a before-after comparative study design. We surveyed the percentage of polypharmacy patients and the number of oral medications before and after feedback, and we performed analyses using a t-test and a chi-square test. The statistical power was set to 80%, the level of significance was set to 0.05, and a sample size of 113 individuals was necessary in each measurement in order to demonstrate significant differences.
All analyses were performed using the SPSS Statistics for Windows 26.0 software package (IBM, Armonk, USA). With the α error estimated at 0.05 and β error at 0.2 (with the power of detection at 0.8), the minimum sample size necessary to compare the difference between the pre-intervention and post-intervention group data was 150 participants for this study.