Clinical Geriatrics

This article is the first in a continuing series on diabetes in the elderly. The series will discuss such topics as quality improvement efforts, the role of exercise and dietary supplements in the management of diabetes, treatment of diabetes with oral and parenteral agents, as well as microvascular and macrovascular complications of diabetes. The second article in the series, “Quality Improvement in the Diagnosis and Management of Diabetes Mellitus in Older Adults,” will be published in the next issue of the Journal.

Diabetes in the elderly is unique. The pathophysiology of this condition is different in the elderly, and, as a consequence, the therapeutic approach should be different.¹

There are a number of reasons why the incidence and prevalence of diabetes increases with age. There is clearly a genetic predisposition to this disease.² If you have a family history of diabetes, you are much more likely to develop diabetes as you age, although the specific genes responsible have not been identified. Diabetes is clearly more common in older people from certain ethnic groups than others, which further supports a genetic predisposition.³

There are also a number of age-related changes in carbohydrate metabolism that allow a genetic predisposition for diabetes to become manifest in older people. These include progressive detriments in glucose-induced insulin secretion (which may be due, in part, to a decreased beta cell response to the incretin hormones GIP and GLP-1) and resistance to insulin-mediated glucose disposal.^4-6

It is abundantly clear that various environmental and lifestyle factors can also increase the likelihood that a genetically susceptible individual will develop diabetes in old age.^1,7 Many older people have co-existing illnesses and take multiple drugs that can adversely impact glucose metabolism. There is an age-related increase in obesity, particularly central obesity, and a reduction in physical activity, both of which can be associated with abnormal glucose metabolism. It is clear that diabetes is more likely to develop in older people who have a diet that is high in saturated fats and simple sugars and low in complex carbohydrates. Moderate alcohol consumption appears to be protective against diabetes, at least in women, whereas greater intake of dietary iron may be associated with an increased risk of diabetes in the elderly. It has been suggested that deficiencies of trace elements such as zinc and chromium and vitamins such as C and E may contribute to the development of diabetes in the elderly, but the data in this regard are unclear. The above information suggests that lifestyle modifications might be of value in the diabetes prevention in older people. In fact, the Diabetes Prevention Program found that modifications of diet and activity were more effective in older people than in younger patients in preventing the development of diabetes.⁸

The presence of inflammation, as evidenced by increased levels of proinflammatory cytokines such as C-reactive protein and tumor necrosis factor-alpha, is associated with an increased incidence of diabetes in the elderly.⁹ On the other hand, higher levels of adiponectin (an adipocytokine that increases insulin sensitivity) are associated with a reduced incidence of diabetes. Lower testosterone levels in men and higher testosterone levels in women also appear to be associated with an increased incidence of diabetes.

Metabolic Alterations
The metabolic abnormalities in middle-aged patients with type 2 diabetes have been extensively studied.^2,10 In both lean and obese subjects, there is an increase in fasting hepatic glucose production, a reduction in glucose-induced insulin release, and a marked impairment in insulin-mediated glucose disposal.