Introduction
Diabetes is one of the leading causes of morbidity and mortality worldwide. According to the International Diabetes Federation (IDF), 463 million people aged 20-79 years worldwide have diabetes of whom 80% live in low-and middle-income countries (LMICs). This number is projected to increase to 700 million by 2045, and most of the rising burden will occur in LMICs. It is estimated that about half of diabetes cases in LMICs are undiagnosed or poorly treated1. Diabetes is associated with an increased risk for a number of serious and sometimes life-threatening vascular complications, including cardiovascular diseases (CVDs), diabetic neuropathy, nephropathy and retinopathy. In fact, CVDs are the most prevalent causes of morbidity and mortality in people with diabetes.
Achieving diabetes control is the ultimate target to prevent or delay early complications of diabetes, which depends on adherence to medications. The World Health Organization (WHO) defines the concept of adherence to medications as the accomplishment of some behaviour, such as taking prescribed medications at the right doses and times in the specified manner as per the recommendation provided by healthcare providers, followed by a lifestyle modification; otherwise, non-adherence exists. For people with diabetes, persistent and compliance with anti-diabetic medication is key to achieving ideal blood glucose levels. Additionally, suboptimal blood glucose control is associated with poor adherence or non-adherence to anti-diabetic medications2,3. However, in many developed and developing countries, non-adherence to prescribed anti-diabetic medications remains a serious problem4. Rates of non-adherence to prescribed anti-diabetic regimens among individuals with diabetes reportedly ranged from 9% to ˃80%5. The non-adherence practice may be particularly higher in LMICs where there is poor accessibility to medicines and healthcare services as well as low level of awareness about the chronic nature of the disease. Indeed, non-adherence to medication contributes to substantial worsening of disease, mortality and increased healthcare cost3. Hence, monitoring of medication adherence is of great importance to achieve optimal blood glucose control.
Globally, several screening tools are available for use to assess medication adherence in individual with diabetes, such as Morisky Medication Adherence Scale (MMAS-8), Medication Adherence Rating Scale (MARS), Brief Medication Questionnaire (BMQ), Self-Efficacy for Appropriate Medication Use Scale (SEAMS) and Hill-Bone Compliance Scale (HBCS). However only few scales are designed to assess medication adherence for people with diabetes in LMICs6. Furthermore, studies on adherence to diabetes medication are being carried out extensively in developed countries and are scarce in LMICs. The available evidence in LMICs come from single-center studies using various measures of adherence. It became necessary and urgently needed to conduct a systematic review and meta-meta-analysis to understand the burden of and factors of non-adherence to anti-diabetic medication among individuals living with diabetes in LMICs, which is crucial in guiding policy-makers to tailor effective strategies to improve adherence to anti-diabetic medication, and consequently blood glucose control. This study, therefore, aimed to summarize available findings of primary studies to determine the level of anti-diabetic medication non-adherence and associated factors reported in LMICs.