Introduction
The use of medicinal plants is common among the elderly. Many elderly patients take medicinal plants arbitrarily under the assumption that they are without risks and side effects. On one hand, elderly patients are at higher risk of serious drug interactions. On the other hand, the effects of non-adherence to medication in this group are more worrying compared to other age groups. The question is whether the use of medicinal plants have an effect on the medication adherence of chronic patients. So far, no study has been conducted in Iran with the aim of investigating the relationship between the history of using medicinal plants and the level of medication adherence in the elderly with chronic diseases. Therefore, this study aims to determine this relationship.
Methods
This is a descriptive cross-sectional study that was conducted in 2020 at Shahid Modares Hospital in Saveh, Iran. Participants were 358 older patients with coronary artery disease, high blood pressure, type 2 diabetes mellitus, and chronic respiratory diseases who were selected by a convenience sampling method. The inclusion criteria were age over 60 years, suffering from coronary artery diseases, high blood pressure, diabetes mellitus type 2 or chronic respiratory diseases, taking at least one medicine for the disease for at least 1 year, not having hearing problems and dementia, the patient’s own responsibility in taking the medication, and the ability to take the medication without the help of others. Exit criteria were unwillingness to continue participation, and incomplete completion of the questionnaire.
The data collection tool was a three-part questionnaire, the first part was a demographic from, the second part was about the history of using medicinal plants in the last 12 months, and the third part of the Morisky medication adherence scale (MMAS) which was developed by Morisky et al. in 2008 and has 8 items. The total score ranges from 0 to 8; score 8 indicates high adherence, score 6-7 shows moderate adherence, and a score < 6 shows poor adherence. In this study, its content validity was confirmed and a Cronbach’s alpha of 0.76 was obtained for its reliability which was acceptable. For the patients who were unable to read and complete the questionnaire, the questionnaire was completed by the researchers on behalf of them.
Results
The mean age of the participants was 69.44 ± 8.13 years. Most of them were female (52.23%), married (87.68%), with junior high school education (71.64%).Regarding the type of disease, according to the patients’ self-report, 169 had a history of coronary artery disease, 292 had a history of high blood pressure, 192 had a history of type 2 diabetes mellitus, and 112 had a history of chronic respiratory diseases. Considering that some patients had a history of more than one disease, the total number is more than 358. The overall mean score of MMAS in the elderly with chronic diseases was 5.48 (poor adherence). Only about 35% had high medication adherence. Moreover, 246 patients (68.7%) had used medicinal plants during the last year, of whom 108 (43.9%) had used at least one medicinal plant during the last week (Table 1).


The results of one-way analysis of variance showed that the relationship between the history of using medicinal plants and medication adherence was significant (P=0.001). For pairwise comparison, Scheffe’s post hoc method was used and the results showed that the mean score of MMAS in those who did not use herbal medicine was significantly different from the other two groups (used with and without the doctor’s prescription) (P<0.05). Therefore, both groups of patients who had a history of using medicinal plants had less medication adherence compared to the group with no history of using medicinal plants. However, there was no statistically significant difference in the mean MMAS score between the two groups of using medicinal plants with and without the doctor’s prescription (P>0.05).
In order to control the effect of demographic variables on the relationship between the history of herbal medicine consumption and medication adherence, logistic regression analysis was used. The results showed that the non-adherence rate increases with the use of medicinal plants, the longer duration of chronic disease, the increase in the number (type) of medicinal plants used in the past week, and the increase in the frequency of using medicinal plants in the past week. For example, the rate of non-adherence to medication in patients who had a history of using medicinal plants without the doctor’s prescription was about 2.09 times higher in patients with no history of using herbal medicine (P<0.001, OR=2.092). 
Discussion
The medication adherence in the elderly with chronic diseases using medicinal plants is poor. Most of them do not inform their doctor about the use of medicinal plants. Necessary education should be provided to the elderly with chronic diseases regarding adherence to medication, the correct way of using medicinal plants, their side effects, herb-drug interactions, and the need to inform the physician about the use of medicinal plants. Obviously, in this way, establishing a reliable relationship and easy communication between the elderly and the treatment team is helpful; it can make it possible for the patients to express their opinions about the disease and the treatments used, including medicinal plants, in a stress-free environment.

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the ethics committee of Saveh University of Medical Sciences (Code: IR.SAVEHUMS.REC1396.08).

Funding
The current research was carried out with the financial support of Saveh Faculty of Medical Sciences and Health Services.

Authors' contributions
All authors contributed equally in preparing all parts of the research.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
Respected officials of Saveh Faculty of Medical Sciences and all the participants in the study are gratefully acknowledged.

References