The use of dietary supplements and OTC drugs was common in elderly patients with chronic diseases, and its use is associated with female sex, higher education, and good economic status. Concurrent use of nonprescription medications with more than 5 prescription medications was not uncommon, but the disclosure rate to the physician was low.
This study showed that 32.5% of Japanese elderly patients with prescription medications for chronic diseases concurrently used nonprescription medication. Previous studies have reported that the use of nonprescription medications is 16.6–66% in the elderly population [15,16,17,18], and 20.2–71.4% in the general population [19,20,21]. The percentage of patients using nonprescription medication in the present study is consistent with previous reports. However, the percentage in our study may be higher than in the general elderly population as all the participants in the present study have chronic diseases with prescription medications.
The present study also demonstrated that dietary supplements are the most commonly used nonprescription medications. Among dietary supplements, vitamins and minerals were the most frequently used, followed by aojiru (green juice) and chondroitin-glucosamine. One study conducted in a hospital in Tokyo reported that health foods including dietary supplements and herbal medicine were commonly used as complementary and alternative medicine (CAM) [22]. Compared to a U.S. report, non-vitamin dietary supplements were different in our study. Echinacea, Ginseng, Ginkgo biloba, and St John’s wort were reported to be popular in the U.S. [7], but such products were not commonly used in the present study. Vitamins and minerals are universally common supplements but other supplements can vary per country and region, thereby reflecting the differences in health system, OTC medications approval, and culture. Aojiru (Green juice), a juice of mixed green vegetables, is very popular in Japan. It is usually not harmful for healthy adults, but it can be risky for patients with chronic kidney disease, as it is enriched with potassium. Chondroitin-glucosamine is one of the most popular supplements in the world, as many elderly patients have orthopedic problems. In this study, use of OTC medications and herbal medicine was less frequent than previously reported in Japan. The reason for this may be that the clinic provides mainly conventional medicines and the patients who prefer to use OTC medications or herbal medicines do not come to the clinic.
Predictors for the use of nonprescription medications were consistent with previous studies. Female sex [2, 7, 15, 19, 21, 23], younger age [2, 16], higher educational qualifications [7, 15, 23], lower income [24], higher income [16], absence of smoking habits [15], living alone [15, 18], retirement [15], and chronic conditions [7] have been reported to be associated with the use of dietary supplements or OTC medications. Contrary to our hypothesis, anxiety, depression, and polypharmacy were not associated with the use of nonprescription medications.
Concurrent use of nonprescription medications with more than 5 prescription medications was frequent in as much as 12.2% of participants. Previous studies also demonstrated high numbers of patients on concurrent use of nonprescription and prescription medications [3, 25, 26]. Elderly patients with chronic diseases are at high risk of drug-drug interaction due to the concurrent use of medications. Research from the U.S. reported the potential interaction between some nonprescription and prescription medications, especially with anticoagulant and antiplatelet therapies [3, 27]. However, one study reported that the actual potential for harm by interaction between prescription medications and dietary supplements was low [28]. In Japan, the risks of interaction between nonprescription medications and prescription medications may be different from other countries because St John’s wort, ginseng, ginkgo, or garlic, which can interact with anticoagulant and antiplatelet therapies, were rarely used in this study.
The percentage of patients given disclosure about their use of nonprescription medications to the physician was low. According to previous studies, 33% to 48.6% of patients taking dietary supplements disclosed this to a healthcare provider [15, 29]. Non-disclosure rates of CAM including dietary supplements were 29% to 77% according to one review [30], recent studies also supported the previous results and questions about the use by a medical practitioner was a major predictor of disclosure [31,32,33]. It is important to collect all information about nonprescription medications considering the potential risk of drug-drug interactions. Medical practitioners should recognize the potential use of dietary supplements and try to ask patients whether they use nonprescription medications. Education for both medical practitioners and patients would be important to increase the disclosure rate. In addition, patients that use dietary supplements should know the potential harm and need to ask doctors if they can take the product, especially elderly patients with chronic diseases who use prescribed drugs.
There are some limitations in the present study. First, this study was conducted at a single facility, so selection bias could have happened. The use of nonprescription medications may be higher in Tokyo than other areas, because the average income in Tokyo is higher than in other areas in Japan. Secondly, there is a possibility of underreporting the use of nonprescription medications, as this study was conducted using a self-administered questionnaire. The rate of reporting the use of supplements through a self-administered questionnaire was demonstrated to be very low [34], but previous studies were also mainly conducted by questionnaires and our data is therefore comparable with others.
As a result, we reported the use and details of nonprescription medications in elderly patients with chronic diseases and its predictors, which are relatively new findings for Asian countries. Further research is needed to examine the relationship between the use of nonprescription medications and actual harm by interactions caused by concurrent use of nonprescription medications and prescription medications.