Patients with diabetes are at risk for a wide range of complications and comorbidities that can affect their ability to care for themselves by following the proper diet, exercising, taking medication, and monitoring blood glucose levels.
According to a 2005 fact sheet from the Centers for Disease Control and Prevention1
* diabetes was the sixth leading cause of death in the United States, being listed as the underlying cause on 73,249 death certificates and as a contributing factor in at least 224,092 deaths.
* heart disease and stroke accounted for 65% of deaths in people with diabetes, in whom the risk of stroke is two to four times greater than in the general population.
* diabetic retinopathy was responsible for 12,000 to 24,000 new cases of blindness.
* 153,730 people had end-stage renal disease related to diabetes (requiring kidney transplantation or dialysis).
* between 60% and 70% of people with diabetes had some form of neuropathy, such as sensory impairment or pain in the feet or hands.
* about 82,000 lower-limb amputations were performed in one year on people with diabetes.
* the costs of medical care and indirect costs such as disability and premature death related to diabetes and associated complications totaled $132 billion.
Most adults with diabetes have one comorbid condition,2 and as many as 40% have at least three comorbid conditions.3 As patients with diabetes grow older, they are at risk for acquiring chronic diseases associated with aging, such as osteoarthritis, dementia, and heart failure. Other chronic conditions, such as thyroid disease, other autoimmune diseases, and any form of cancer can also complicate the medical management of diabetes. For example, hyperthyroidism alters glucose metabolism and leads to hyperglycemia, whereas hypothyroidism leads to hypoglycemia.4
REVIEW OF THE LITERATURE
Although some research lends support to the theory that complications and comorbidities can affect diabetes patients' ability to manage their self-care, a literature review did not find any systematic, randomized, quasi-experimental, or comparative studies to confirm this theory. It is extremely difficult to conduct randomized, controlled trials of diabetes education and self-care, and it is almost impossible to do a blinded study with a control group. For example, a study would be unlikely to have experimental and control groups with identical complications of diabetes and comorbidities. Therefore, most studies have been observational, descriptive, correlational, or qualitative in design. No research has directly addressed the question of whether complications and comorbidities affect the ability to perform diabetes self-care.
With the specific objective of evaluating quality of life in relation to demographics, medical history, and self-management characteristics, Glasgow and colleagues conducted a survey of more than 2,000 people with diabetes.5 They found that those patients with fewer complications or fewer comorbid diseases and those who had not been hospitalized in the past year had a higher quality of life. The self-reported amount of exercise was the only significant self-management behavior to predict quality of life. This study did not determine whether a higher quality of life leads to better self-care.
Thomas and colleagues evaluated physical activity in a diabetes clinic population.6 Among the 406 questionnaires returned, 20% cited serious illness as the reason for not participating in physical activity. One limitation of this study was the definition of physical activity as any exercise or sport performed in the prior two weeks. This definition of physical activity is less than the recommended 150 minutes per week.7
Pain is a frequent result of diabetes complications and comorbidities. Krein and colleagues conducted a cross-sectional study on the effect of pain on the ability of 993 patients with diabetes to self-manage.8 In this well-designed study, 60% of the respondents reported chronic pain. Patients with chronic pain had poorer overall diabetes self-management and more difficulty following recommended exercise and dietary plans. Patients with severe or very severe pain reported significantly poorer diabetes self-management than those with mild or moderate pain, including more difficulty taking medications and exercising.
Zgibor and Simmons evaluated barriers to self-testing of blood glucose levels in 323 patients without complications of diabetes.9 They found that comorbid conditions and adverse effects of medications did not influence the performance of blood glucose self-monitoring. The most significant barriers to glucose monitoring were related to finances and access to care.
Although it seems logical that low vision would affect the ability to perform diabetes self-care, no studies have specifically evaluated the effect of low vision or loss of vision on diabetes self-care behaviors. Studying 199 patients with macular degeneration (rather than diabetes), Stevenson and colleagues found that those with the lowest vision were least able to provide care for themselves and others.10
In a cross-sectional correlational study of 309 patients with type 2 diabetes, Aljasem and colleagues included complications as one of the many variables related to self-care.11 The only complication-related correlation noted was that patients with complications (which were not specified) were more likely to skip medication. Complications did not affect other self-care behaviors, including eating, exercising, testing blood glucose levels, and adjusting insulin doses. The study did not examine whether skipping medication contributed to the development of complications or whether the complications caused patients to miss medication doses.
How much time do patients with diabetes invest in self-care? This is the question that Safford and colleagues asked in a survey of 1,482 people with diabetes enrolled in three managed care plans.12 On average they spent 48 minutes per day on diabetes self-care. Patients with severe neuropathy were more than twice as likely to spend time caring for their feet as those without symptoms, but one in four of them reported spending no time on foot care.
Depression affects the performance of self-care13 (see "Psychosocial Issues and Self-Care," page 34). The effects of other chronic conditions on diabetes self-care have not been studied formally.
As a clinician, I have observed that diseases such as cancer, severe heart failure, and chronic obstructive pulmonary disease and their treatment not only make it difficult for patients to engage in self-care but also make control of blood glucose levels extremely difficult. For example, heart failure alters tissue perfusion and therefore requires adjustment of medication doses or insulin, based on overall fluid load. Many patients undergoing treatment for cancer have difficulty eating, leading to low blood glucose levels; but the steroids given before chemotherapy raise blood glucose levels.
How do the patient and the provider determine priorities of care when other serious chronic diseases are also present? Piette and Kerr have suggested a conceptual model that can aid in answering this question.14 These researchers maintain that tallying the number of complications or focusing on individual complications may oversimplify the effect of chronic complications or comorbidities on diabetes self-care.
Piette and Kerr have proposed a framework for understanding how comorbid chronic conditions may influence medical care, self-management, and outcomes in patients with diabetes (see Figure 1, page 56).14 The model suggests intervention points where systems of care for patients with diabetes and comorbid diseases can be improved, using strategies such as increasing patients' resources for self-management. One way to do this would be to make follow-up telephone calls between office visits. The model also helps clinicians identify important priorities during patient visits, including those related to both management of diabetes and management of comorbidities. This framework may guide both researchers and health care systems as they investigate and develop more effective models for improving care. The model may also clarify why diabetes-specific health care changes could have no effect on the patient's overall functioning, health status, or use of health care services.
Various comorbidities may have different effects on the way patients manage their diabetes or the way providers approach treatment recommendations. Piette and Kerr have proposed categories of comorbid chronic conditions to clarify this point (see Table 1, page 57).14 The model suggests that some comorbid conditions are so serious that they overshadow all other diseases, including diabetes. Examples of such clinically dominant comorbid diseases include stage 4 lung cancer and New York Heart Association class IV heart failure, both of which can shorten life expectancy. Concordant conditions, such as hypertension and diabetes, have the same overall risk profile and represent different aspects of the same pathology. Discordant conditions are those that are not directly related to diabetes, in either pathology or management. The final category of comorbid chronic conditions is symptomatic versus asymptomatic.
DIRECTIONS FOR FUTURE RESEARCH
There are many unanswered questions about the effect of complications and comorbidities on diabetes self-care. For example, how does a patient prioritize self-care behaviors in relation to self-care of complications or comorbid diseases? Patients and providers alike need guidance on prioritizing treatment goals and selecting the most important self-care behaviors. Research is needed to more clearly identify barriers to self-care and to develop ways to assist patients with diabetes and comorbidities to improve their health and quality of life.
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6. Thomas N, et al. Barriers to physical activity in patients with diabetes. Postgrad Med J
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8. Krein SL, et al. The effect of chronic pain on diabetes patients' self-management. Diabetes Care
9. Zgibor JC, Simmons D. Barriers to blood glucose monitoring in a multiethnic community. Diabetes Care
10. Stevenson MR, et al. Reduced vision in older adults with age related macular degeneration interferes with ability to care for self and impairs role as carer. Br J Ophthalmol
11. Aljasem LI, et al. The impact of barriers and self-efficacy on self-care behaviors in type 2 diabetes. Diabetes Educ
12. Safford MM, et al. How much time do patients with diabetes spend on self-care? J Am Board Fam Pract
13. Ciechanowski PS, et al. Depression and diabetes: impact of depressive symptoms on adherence, function, and costs. Arch Intern Med
14. Piette JD, Kerr EA. The impact of comorbid chronic conditions on diabetes care. Diabetes Care