Diabetes mellitus (DM) is a serious and a rapidly growing public health problem that affects millions of people. It usually co-exists with other medical conditions, and its prevalence is increasing year by year reaching epidemic proportions. Currently, 387 million people have DM (1) and are expected to reach 483 million and 592 million by the year 2030 (2) and 2035 (1), respectively, in which type 2 DM is accounting 90% of cases (3). DM is responsible for more than 77% of morbidities and 88% of deaths in developing countries (1, 4).

It is noteworthy mentioning that 15 years later the Arab world in North Africa, the Middle East including Gulf area, is going to have a tremendous increase in the percentage of people having DM compared to other parts of the world (5). According to the International Diabetes Federation, the prevalence of DM in the Middle East and North African region will be the highest compared to other parts of the world (6).

In Palestine, few studies were conducted and the prevalence of DM was higher in urban areas compared to rural areas (7–9). Abu-Rmeileh and colleagues (10) estimated the prevalence of DM in Palestine at 20.8 and 23.4% in 2020 and 2030, respectively. Reports of the Ministry of Health (MoH) revealed that 27,601 have DM in the Gaza Strip with an incidence rate of 15.4/1,000 (11) and is steadily increasing because Gazian people are in a prolonged state of stress from political uncertainty and frequent violation. DM is known to be the disease of elderly; however, it is now more prevalent among younger age below 55 years old. Patients with DM are in an unhealthy class due to lack of knowledge about the disease and prevention of complications. Moreover, the increasing rate of obesity is the major risk factor for DM (12). Complications from DM, including diabetic foot, were previously studied in Gaza and showed to be significantly associated with a low educational level, low income, and primary care physicians’ attitudes (13, 14). DM represents 11.2% of all deaths (11), and half of physicians and nurses do not adhere to Palestinian diabetes guideline because of lack of interest (15) making real challenges to the health care services and proper diabetes management. Diabetic neuropathy is one of the major complications that presents in 12% of type 2 DM patients and is the leading cause of extremity amputations (11).

Achieving glycemic control and preventing early complications are the ultimate targets of diabetes management which depends on patient’s adherence to regimens (16). Adherence to prescribed medications is one of the key dimensions of health care quality, which is defined as the proportion of prescribed doses of medication actually taken by a patient over a specified period of time (17). Adherence to or compliance with medications has significant economic and therapeutic consequences (18), because non-adherence patients are at greater risk of developing complications affecting their health status and overall quality of life (19).

Patients’ adherence to their anti-diabetic medications is a critical and important factor to prevent serious undesirable complications and to reduce the health care resource utilizations. Effective diabetes management mandates good provider–patient relationship, and compliance to therapies is one of the significant aspects of the relation. Poor adherence to therapies is common, especially when comorbidities exist (20), and is believed to be influenced by several factors divided into five categories: patient-centered factors, therapy-related factors, health care system factors, social and economic factors, and disease-related factors (21–23).

Studies on adherence to anti-diabetic medications among type 2 DM patients in Palestine are few (24–26), but unfortunately none of these were carried out in the Gaza Strip. It became necessary and urgently needed to highlight the current status of adherence to diabetic medications among type 2 DM patients in the area of Gaza Strip and show the cultural differences within the same Palestinian population, with Arab-speaking countries and the overseas world. Thus, the aim of this study was to evaluate the adherence to anti-diabetic medications and examine the associated factors among type 2 DM patients attending primary health care clinics in the Gaza Strip. In addition, this study was based on the following hypotheses: –

Adherence to anti-diabetic medication is sub-optimal among primary health care patients with type 2 DM in the Gaza Strip.

Three hundred and sixty-nine patients participated in the study, and their mean age (±SD) was 56.38 ± 10.36. More than half (55.8%) were females and 352 (95.4%) were married. With regard to clinical characteristics, 180 (48.8%) have no comorbidities; 42 (11.4%) have hypertension; 26 (7%) have retinopathy, and 104 (28.2%) presented with nephropathy. A majority of patients (321; 87%) were not previously hospitalized and were under oral hypoglycemic agent (241; 65.3%), while 85 (23%) were under insulin treatment. Mean duration (±SD) of having DM was 10.48 (8.12) and two-third of them have DM for more than 5 years (234; 63.4%). Good glycemic control (≤6.4%) was found in 41 (11.1%) patients.

In our study, we reported 214 (58%), 146 (39.5%), and nine (2.5%) of primary care patients with type 2 DM, under treatment with either oral medications alone or with insulin, had high, medium, and low adherence, respectively. The information on adherence was based on patients’ recall, and therefore the actual and true prevalence of compliance could be lesser than the presented findings in this study. In addition, patients might have difficulties in remembering their habits and medications taking practices, but this was diminished by asking patients to memorize within a period of 2 weeks only. The reported adherence to this study was suboptimal and lower than previous findings reported from Iran (74.8%) (35), and Nigeria (72.5%) (36). However, Ahmad et al. (37) reported a lower rate of adherence than our finding (47%). The differences in adherence level could be attributed to factors related to the health care settings, and/or socio-economic status, and/or metrics used for adherence assessment. Another possible explanation could be the context of Gaza Strip, in which the treatments are only available for few days from the beginning of each month, and therefore if patients did not get their treatments on time, they have to buy them from own pockets, which overburden the financial and economical responsibility of patients to afford the necessary medications. However, treatments could be available for free in other contexts.

We also found that the level of adherence to medications was associated with patients’ belief about the severity of disease, which reflects the feelings concerning the seriousness of contracting an illness or leaving it untreated. This is enough explained on health psychology model presented in HBM and the Theory of Planned Behaviors (30, 38). The majority of our primary care patients sensitized the severity of DM on their health in future, and therefore 94.6% stated that they are in need for diabetes treatments. Negative beliefs about medications and disease are a potent barrier factors to proper adherence (39, 40). It is necessary to address patients’ belief about the severity of disease, the benefit of treatments, and possible challenging factors, through health education, that contribute to preventing patients from adherence to their therapies. Many studies, from Europe, Africa, and the USA, ensured the importance of having diabetes health education to improve patients’ adherence to their medications (41–43). There is a need to raise patients’ awareness and sensitization about disease and management plan. Possible ways to achieve it could be through the self-management education of diabetes, meeting with a diabetes educator on a regular basis, use of educational materials, establish a community campaign, improve communication between patients and health care providers, and patients’ self-management of diabetes (44).

Females were more likely than males to be adherent to their therapies which is consistent with a research conducted among patients suffering from tuberculosis in Thailand (45). The gender’s effect on adherence rate is contradictory, in which previous studies have shown non-adherence was associated with female (46, 47). A possible explanation for our findings, but remains a source of speculations, is that women are more proactive than men toward following preventive care and seeking medical care to obtain treatments for medical conditions. Moreover, adherence to anti-diabetic medications is challenged with complex regimens especially when comorbidities exist, and so men forget to take their therapies as they are exhausted with work. In addition, a possible higher rate of medications’ side effect could be a reason behind low adherence among men. Also, some studies did not find possible relations between gender and adherence to medications (48, 49).

Old age (≥60 years) was a predictor of good adherence, but the finding was not statistically significant. A recent systematic review conducted by Krueger et al. (50) reported similar findings regarding the relationship between older age (>60 years) and adherence to medications among patients with congestive heart failure. Other studies of patients with heart problems were also in line with our finding (51, 52). Common cause for non-adherence among younger ones could be attributed to new diagnosis (53), limited knowledge of the disease (54), fear of side effect, and burden of regimens (55, 56). Older patients with longer duration of having the disease receive proper support for diabetes management and are more aware of the importance of glycemic control to prevent potential complications and so survive with better quality of life (55). Furthermore, social support given by families in Gaza to be in charge of elderly could be one of the contributing factors to adherence to medications.

Duration of DM was predicted to be an important factor related to adherence to medications but was not statistically significant. The longer the patients have diabetes history, the more likely they will be adherent to the prescribed regimens. This finding is consistent with previous publications (57). A possible explanation is that patients during the early years of disease are not aware of the risk of disease and its serious complications. But when complications start and suffering from disease begins, the attitude toward the disease and related therapies may change leading to a better adherence to medications and providers’ instructions. Furthermore, patients with longer duration of disease are more likely to interact better with their health care providers, understand their treatment plans, and become more aware of their diseases. However, Giemens et al. (58) and Arifulla et al. (59) found a negative relationship between the duration of diabetes and patients’ adherence to medications. Sweileh et al. (60) found no significant relation between the duration of DM disease and adherence to treatments. In view of controversies, we recommend further prospective studies to improve future management and to find out the possible contribution of adherence to medications to patients’ survival.

This study has many limitations: first, the use of self-report method and the simplest and inexpensive method, to evaluate patients’ adherence to anti-diabetic medications. Second, self-report methods usually over-estimate patients’ adherence level. However, Goerge et al. (61) stated that using a valid scale such as the MMAS, the measured adherence level is accurate since the sensitivity and specificity are more than 70%. Third, there was a lack of information about the history of joining educational sessions about diabetes, and the level of education. Fourth, selection bias could happen among primary care patients since those who seek health care are only who care about their health and best. Fifth, reasons for non-adherence were not addressed in this study. The strengths of this study are: first, the randomization applied when selecting PHC and patients; second, gender representativeness in the study sample; and third, the sample size was relatively large and enough to evaluate adherence and factors associated.

This study showed that patients’ adherence to anti-diabetic medication was suboptimal and variations were found between high adherent and intermediate adherent with regard to, but not limited to, age, gender, duration of DM, health literacy, health belief, and the absence of co-morbidities. The longer duration of having the disease, old age, female gender, and patient’s self-perception and belief about the severity of DM are factors associated with adherence to medications. Enhancing patients’ knowledge and recognition with diabetes, through diabetes educator, is necessary to improve self-management of DM and increase the rate of adherence. Increasing interactions and have a partner relationship with patients are keys to improve patients’ adherence to medications.

This study received the ethical approval from Palestinian Ethical Research Committee (No: PHRC/HC/118/16 on 06/Jun/2016). This is an independent regional body that comprises members of government and external professionals and researchers. A permission was also obtained from Ministry of Health to visit the selected primary health care centers and conduct the study. Patients were informed about their right to withdraw from the study at anytime without any harmful consequences. Moreover, we verbally stressed on the voluntary participation in the study, giving the right to withdraw at any time without any consequences. The study was conducted over a period of 3 months starting from October 2016.

AE, MR, and HS developed the conception and design of this study; AA analyzed and interpreted the analyzed data; AE drafted the manuscript; AE, MR, AA, and HS revised the manuscript, provided final approval of the manuscript, and approved this manuscript.

The authors declare that there is no conflict of interests regarding the publication of this paper.