Background
Recent studies have shown that the prevalence of over-the-counter (OTC) medications and use of dietary supplements in older adults is increasing [
1,
2]. The use of such drugs and products by elderly patients with chronic diseases needs to be particularly considered, because the drug metabolism in these patients is deteriorated due to their age. Nevertheless, concurrent use of nonprescription medications with prescription medications is common according to a study conducted in the United States (U.S.) [
3]. It is difficult for medical practitioners to know the use of nonprescription medications as these are used at the discretion of the patients. In addition, previous reports suggested that many patients taking nonprescription medication do not tend to disclose the use of these drugs to their physician [
4,
5].
A systematic review about self-medication in the elderly population reported that the prevalence of self-medication varied between 4 and 87%, and was associated with female sex, visits to pharmacists, depression, functional dependency, recent hospitalization, oral pain, restriction of activities and physical inactivity [
6]. Another research study conducted in the U.S. reported that factors associated with dietary supplement use in patients taking prescription medication were female sex, Hispanic ethnicity, higher education, lack of medical insurance, and chronic conditions [
7]. While depression was associated with the use of complementary medications in cancer patients [
8], only one study reported the association of depression with the use of multiple nonprescription medications in the elderly population [
9]. Overall, the association of anxiety or depression with the use of nonprescription medications was not well assessed in previous studies in elderly patients with chronic diseases.
Most of the previous studies on the use of nonprescription medications were conducted in a limited amount of countries and with areas mainly in the U.S. or Brazil, and reports from Asian countries are few. The use of nonprescription medications can be different per country and area, as it is dependent on the access to medical care, health system, and cultural differences. However, the use of dietary supplements and OTC medications and the predictors for its use are not well studied in Japanese elderly patients.
In this study, we aimed to describe the use of nonprescription medications including dietary supplements and OTC medications, and additionally identify the predictors for its use in elderly patients who use prescription medications for chronic diseases in Japan. We also hypothesized that depression or anxiety is associated with the use of nonprescription medications.
Discussion
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‐
18], and 20.2–71.4% in the general population [
19‐
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‐
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.
Conclusions
Our results show that the use of nonprescription medications was common in elderly patients with chronic diseases. The type of the nonprescription medications were mainly dietary supplements including vitamins/minerals, aojiru (green juice), and chondroitin-glucosamine. Female sex, higher educational qualifications, and good economic status were associated with the use of nonprescription medications. Concurrent use of nonprescription and prescription medications, even with more than 5 prescription medications, were common in elderly patients, and the disclosure rate of the use of nonprescription medications was low. Therefore, medical practitioners should ask about the use of nonprescription medications and assess the potential drug-drug interaction with prescription medications.