Barriers to insulin treatment in patients with type 2 diabetes mellitus

KEYWORDS:

• Type 2 diabetes mellitus
• insulin
• adherence
• hypoglycemia
• psychological insulin resistance

Due to the progressive deterioration of beta-cell function during the course of type 2 diabetes mellitus (T2DM), many patients with long-standing T2DM will eventually require insulin treatment [1]. However, several studies showed considerable delays in the initiation of insulin, even in the presence of T2DM-related complications [2,3]. It has been reported that after 5 years of failure of oral antidiabetic therapy, half of patients with T2DM will not have started treatment with insulin [3]. In a more recent study, the mean glycated hemoglobin (HbA_1c) levels at initiation of insulin were 9.6% [4].

Several factors, both patient- and physician-related, contribute to these delays in the initiation of insulin treatment. Approximately 28–50% of patients who are recommended to start insulin are unwilling to accept this treatment [5,6]. In addition, 70% of patients with T2DM consider it unlikely that they will require insulin treatment in the future [5]. Fear of hypoglycemia appears to represent the strongest barrier to insulin treatment [5–10]. Reduced flexibility, beliefs of insulin therapy permanence, and feelings of failure also represent obstacles for accepting insulin treatment [5,6,10]. The majority of patients also regards insulin as a sign of T2DM deterioration and is preoccupied by the notion that their family or friends will be more concerned about them when they start insulin [5]. An interesting study also reported a fear of addiction to insulin treatment and a perception that glycemic control was not inadequate enough to necessitate insulin administration [9]. Poor general health and depression are additional risk factors for psychological resistance to insulin treatment [5]. Female gender and non-white ethnicity are also associated with greater reluctance in using insulin [6,7]. On the other hand, better perceived interaction with health care providers was associated with lower level of resistance to insulin treatment [7]. Stronger belief in the value of tight glucose control also predicts less reluctance to use insulin [7]. However, and despite the established glucose-lowering efficacy of insulin, most patients rate its effectiveness as low [11]. On the other hand, poor perceived glycemic control and presence of T2DM-related complications and distress are associated with higher odds of perceiving insulin as efficacious [11]. It should also be emphasized that patients associate insulin use rather than hyperglycemia with diabetic complications. This is partly because patients with T2DM have multiple relatives with this disease and note that soon after insulin initiation, complications such as renal failure or amputation occurred. Moreover, cultural characteristics pose different barriers in the acceptance of insulin treatment. Indeed, more Mexican Americans than non-Hispanic whites believe that insulin causes blindness, whereas the belief that insulin causes erectile dysfunction appears to be more widespread among African-Americans [12].

Regarding the physician-related barriers to the timely initiation of insulin treatment, the fear of hypoglycemia is also an important obstacle [9,10]. In addition, patients with T2DM who require insulin treatment are often elderly and have impaired renal function, which further increase the risk of hypoglycemia [13–15]. Beliefs about patients’ fear of injections, concern about pain associated with both injections and glucose self-monitoring hardship in using insulin are also considered barriers to insulin treatment [9,16,17]. However, it should be emphasized that these perceptions appear to be infrequent among patients with T2DM and do not appear to substantially affect their willingness to initiate insulin treatment [5,7,9]. Concerns that adherence to insulin treatment will be less optimal than to oral glucose-lowering agents are also prevalent among physicians and might affect their decision to administer insulin [9,17]. On the other hand, physicians who believe that their patients are adherent to treatment are more likely to initiate insulin [11]. Interestingly, many physicians believe that insulin should be prescribed only after oral antidiabetic treatment has failed [17]. In addition, a substantial proportion of physicians appear to have doubts regarding the effects of insulin treatment on cardiovascular events [17]. On the other hand, several studies showed that specialists are more likely to initiate insulin in response to elevated HbA_1c levels than primary care physicians [11,18]. Moreover, physicians who exhibit greater inertia in uptitrating or adding additional oral antidiabetic agents are also more likely to delay the initiation of insulin treatment [11]. On the other hand, physicians who consider insulin to be more effective are more likely to initiate this treatment [11]. Importantly, the additional time needed to educate patients on the use of insulin and physicians’ experience with the use of insulin does not appear to represent major barriers to prescribing insulin [16,17]. The risk of weight gain also does not appear to make physicians more reluctant to recommend insulin treatment [9,17].

Given the multitude of factors contributing to resistance to insulin treatment, a comprehensive approach is essential for overcoming these barriers. First, it is important to discuss in detail with the patient her/his concerns regarding insulin and to dispel common misconceptions [19]. It is important to inform the patient that initiation of insulin treatment not only improves glycemic control but was also shown to improve the quality of life, mostly due to improved glycemic control [20,21]. Patients starting insulin also appear to be more satisfied with insulin than with oral antidiabetic treatment and to be more willing to recommend this treatment to other patients [9,22]. Moreover, timely use of insulin reduces the risk of T2DM-related complications [23]. Education of the physicians, particularly the non-specialists, regarding the efficacy, safety, and cardiovascular benefits of insulin is also essential for the implementation of this treatment in the appropriate patients with T2DM.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

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Funding

This paper was not funded