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 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." We determined the survey items based on focus group discussions and the 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. Factors contributing to polypharmacy were studied in both groups. 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 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.
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). We instructed those who responded that the results were unexpected to further assess the expectations for part of the survey from Study 1; namely, the results from the questions, "Do you feel that the prescribed medications were necessary? Do you understand the reasons why the medications were prescribed? Would you be worried if your medications were deprescribed? Is it difficult to ask your doctor to deprescribe your medications?" The health professionals' answer options were: "more than expected," "as expected," or "less than expected." (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.