The term brittle diabetes was coined in 1934 by Woodyatt to describe individuals with unexplained large changes in blood glucose concentration. In 1977, Tattersall added to the concept, "any patient whose life is constantly being disrupted by episodes of hypo- or hyperglycaemia, whatever their cause." Despite decades of awareness about this condition, there is no specific definition or criteria for the diagnosis, and there are no guidelines to manage it. In fact, the existence of the diagnosis and its etiology and mechanisms are still being debated. Most patients with brittle diabetes are females in the second and third decade of life, but recent studies suggest that there is a second peak of prevalence at 60 to 70 years of age (Benbow et al., 2001). There is a paucity of published information on brittle diabetes in the elderly. This article will review brittle diabetes as seen in the general population and highlight issues for geriatric patients.

Recent studies have increased our understanding of the characteristics of brittle diabetes. A British study identified 414 brittle diabetics (all ages) by sending a questionnaire to diabetes clinics in the United Kingdom (Gill et al., 1996). The mean age of these patients was 26 years (

standard deviation [SD] of 15 years) with a small peak at 60 to 70 years of age. Most patients were female (66%), and overall prevalence was 1.2/1000 patients with diabetes. The most common form of brittleness seen was recurrent ketoacidosis in 59% of patients, with hypoglycemia in 17% and mixed instability in 24%. Over half of the physicians responsible for the care of these patients offered causes for the brittleness; 93% considered psychosocial factors as the most likely cause. Organic conditions, such as lack of hypoglycemic warnings and alcohol abuse, were also mentioned. Compared with young patients with ketoacidosis, older patients are more likely to have mixed-type brittle diabetes or recurrent hypoglycemia (Gill and Lucas, 1999).

A similar questionnaire circulated to adult diabetes clinics in the U.K. explored the characteristics of brittle diabetes in the elderly (Benbow et al., 2001). Fifty-five patients were identified as experiencing life-disrupting glycemic instability associated with admissions to the hospital. The mean age was 74 years, again with a female majority (71%). Mean duration of diabetes was 24 years, and mean duration of brittleness was nine years. In contrast to the previous survey of brittle diabetics of all ages, elderly patients with brittle diabetes were more commonly of a mixed unstable type (44%). Twenty-nine percent had recurrent ketoacidosis and 27%, recurrent hypoglycemia. In only four cases was deliberate manipulation of therapy considered a possibility. Two-thirds of cases were felt to have multiple origins. Single causes included medical disease in 14% and hypoglycemic unawareness in 6%. Memory or behavioral problems were seen only in 8% of cases but may have a role in other multiple causes of brittleness. This difference in characteristics between brittle diabetics as a whole and the elderly brittle diabetic subset likely indicates differing etiologies of brittleness.

In 1985, Schade and colleagues reported on their findings in 30 patients referred to University of New Mexico for evaluation and treatment of brittle diabetes requiring multiple hospitalizations despite extensive training and diagnostic testing (Schade et al., 1985a, 1985b). These were patients who had previously failed intensive insulin management programs. The results yielded a diagnostic algorithm that successfully established an etiology for diabetic brittleness in 29 of these 30 difficult patients (Schade et al., 1985b). In these case studies, surprisingly, half of the patients were found to have factitious disease or malingering. Another 25% of the patients were felt to have a learning disorder evident on psycholinguistic testing that affected their ability to manage diabetic instability. Insulin resistance and gastroparesis with resultant delayed absorption of food in relation to peak insulin activity were identified as other causes of brittleness (Schade et al., 1985a).

The 30 patients in the Schade et al. case studies had characteristics similar to those identified in the Gill et al. 1996 survey of 414 brittle diabetics: young females with predominantly hyperglycemic instability, and the majority of cases of brittleness were due to psychosocial factors. However, the results of the Schade et al. study are less compatible with the patient characteristics seen in the Benbow et al. 2001 survey of 55 brittle diabetics over the age of 60. In this patient group, a much lower percentage of patients were felt to be deliberately manipulating their brittleness. Instead, the cause of brittleness was deemed multifactorial in two-thirds of the cases. Dementia and behavioral problems were felt to be possible contributing causes in approximately 20% of cases.

Focused history and examination. Evaluation of a patient with brittle diabetes begins with a careful history. Points to highlight include age at which diabetes was diagnosed; past medical regimens and diabetic educational programs; type of brittleness (predominantly hyperglycemic, hypoglycemic or mixed); circumstances surrounding extreme glucose fluctuations; concurrent illnesses; and social history, including drug and alcohol use. In surveys involving all age groups, psychosocial factors were felt to be a major cause of brittle diabetes (Gill et al., 1996). The burden of monitoring blood glucose at home and the impact of these fluctuations on the patients' lives can be tremendous, particularly in the elderly (Modawal and Rudawsky, 2001). Practitioners should appreciate the impact of life stressors and resultant anxiety and depression on the ability of patients to manage their disease. In addition, a high degree of suspicion for factitious disease and malingering must be maintained -- particularly in the young.

Functional assessment. Attention should also be paid to patients' functional abilities. In older patients with diabetes especially, factors such as poor vision, arthritis, dementia, and inability to obtain medications and supplies may limit their ability to manage diabetes. If functional limitations are suspected, specific interventions to overcome them should be explored. When dementia limits a patient's ability to manage their diabetes, educating caregivers to assume control of diabetic management or facilitating a patient's move to a living situation with a higher level of care may be necessary.

Other complications. Additional conditions to suspect in cases of recurrent ketoacidosis are occult infections (e.g., sinusitis, osteomyelitis or urinary tract infection) and drug or alcohol withdrawal. Focused history with a review of drug effects and interactions (e.g., ß-blockers may blunt hypoglycemia) should be considered. Gastroparesis, hypoglycemic unawareness and other endocrine disorders should be excluded in cases of recurrent hypoglycemia. Gastric emptying studies and therapy with metoclopramide (Reglan) may be helpful in cases of gastroparesis (Schade et al., 1985b). However, expectation of improvement in metabolic control should be tempered, as this has not been conclusively shown to result from therapy with other prokinetic agents (Stacher et al., 1999). An evaluation for hypothyroidism and adrenal insufficiency can also reveal treatable causes of recurrent hypoglycemia.

Diabetic education. Trained diabetic educators can evaluate the patient's understanding of diabetes management, exercise and dietary compliance and can directly observe the patient's ability to perform glucose monitoring and insulin injections. In 1995, Schade and Burge found learning disorders were a major cause of brittleness in a significant number of patients, and a significant number of these patients benefited from specific treatment.

Goals of treatment. Management of brittle diabetes will vary depending on the underlying etiology and age of the patient. Tight glucose control is generally not a realistic goal for patients with brittle diabetes due to risk of hypoglycemia. Therapy should be aimed at avoiding excessive hyperglycemia and hypoglycemia and keeping patients as asymptomatic as possible. This is especially relevant when treating older adults, where minimizing long-term complications is less of a priority than avoiding extremes in serum glucose. Older adults have a shorter life expectancy in which to develop long-term complications and have a significantly higher mortality in cases of ketoacidosis (Gale et al., 1981).

Insulin therapy. Treatment generally involves multiple daily injections of regular or lispro insulin titrated to glucose determinations. In addition, intermediate-acting insulin, either as a separate injection or as a premix with morning and evening injections of regular insulin, is frequently used twice daily for continuous insulinization. Changes to both short- and intermediate-acting insulin doses should be made in small increments. Insulin continuous infusion pumps may be beneficial in selected cases, although patients must be carefully selected. Insulin pumps can create problems in the older patient due to the complicated mechanism of insulin delivery and, therefore, are seldom used. (See related article -- Ed.) The role of insulin analog or insulin glargine for 24-hour basal glucose control remains to be clarified for brittle diabetes.

A small number of patients with diabetes mellitus have brittle disease. These patients can be difficult to manage and may require multiple hospitalizations. The majority of brittle diabetics are young women, but a smaller peak is seen among elderly patients. While the exact prevalence of brittle diabetes in the older population is not known, this condition will be encountered more often in the future due to changes in population demographics and use of insulin. The etiology so far points toward psychosocial factors in the young. In contrast, elderly patients with brittle diabetes may be more likely to have multiple causes with mixed hypo- and hyperglycemic episodes, rather than recurrent episodes of ketoacidosis. A thorough history with observation of a patient's self-management skills and a high suspicion of psychosocial factors impacting brittleness are key components to evaluation. Treatment is aimed at avoiding excessive hyper- and hypoglycemia and alleviating symptoms, as tight control is not often possible.

Dr. Haine is a fellow in geriatric medicine at University of Cincinnati Medical Center.

Dr. Modawal is a geriatrician and assistant professor of family medicine at University of Cincinnati Medical Center.

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Brittle Diabetes Mellitus in the Elderly