In the eastern region of Bhutan, with an overall mean score of more than 6, adherence to anti-diabetic treatment was at the intermediate level. Close to 60% of patients have either a high or an intermediate level of adherence. Similar to the global adherence rate of below 50% [6], [7], [13], the studies conducted in the U.K. and the U.S.A. reported poorer adherence rates [4], [8]. A study in China reported an adherence rate of only 47% of patients taking prescribed oral drugs [14]. However, in India, the prevalence of good medication adherence was reported as 74.5% [15], the highest adherence rates reported so far. These studies were, nonetheless, conducted on patients taking an oral anti-diabetic drug.
Comparatively, the study noted that Samdrup Jongkhar district scored the lowest adherence score whereas Trashi Yangtse scored the highest. Although the proportion of participants in these two districts was not comparable, the low health literacy rate [4] in the population may be a risk factor. Study in rural India, Kerala, reported a high prevalence of poor adherence of 74% [16]. In agreement, this study also demonstrated that the lowest level of adherence was in the remote district of Bhutan, where health literacy is poor. Further supporting this argument, another study also stated that the level of education had a positive influence [9] on the improvement of medication adherence [7], [9]. The difference in adherence level between hospitals may also be due to differences in accessibility and management approach of DM. However, in this study, there is no significant difference among groups taking different travel times to reach the nearest health facilities.
Further, this study also found that few risk factors had a statistically significant association with the level of adherence. As reported by other studies [7], [10], patients prescribed on two or more different types of anti-diabetic drugs reported poor medication adherence compared to those who were prescribed on only one type of drug. Advising several drugs together, the treatment regimen becomes complex and forgetful. As demonstrated by several studies [17], [18], it is clear that a fixed-dose combination with fewer numbers of drugs can reduce the rate of non-adherence. Bhutan as the least developed country with a free healthcare system, it is yet to make a change from multiple drugs to a single-dose or fixed-dose combination system. This study demonstrated that participants experiencing adverse drug reactions had poorer adherence. Other studies have also shown a causal relationship between adverse drug reactions and the level of medication adherence [19].
The study has few strengths. This study was conducted in a unique setting where healthcare service is free of cost. We also included participants taking both oral and injection forms of anti-diabetic drugs. Addition to this, the data has also been sourced from six eastern districts and one regional hospital. However, the authors also admit a few limitations to this study. The analysis of the association between risk factors and the means of adherence scores was done without adjusting co-founders. We opted for univariate analysis of risk factors of interest as it was not our primary research question.
Though it is premature to draw any conclusion with just one study in the eastern region of Bhutan, the study recommends the need for further studies on risk factors affecting the level of medication adherence of DM throughout Bhutan.