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Placing the risk of diabetes in context: based on an interview with Leslie Citrome, MD, MPH.

Article Excerpt
As of 2005, an estimated 20.8 million people in the United States, or 7% of the population, have diabetes; one-third (6.2 million people) are undiagnosed. In 2005, 1.5 million new cases of diabetes were diagnosed in people aged 20 years or older. By 2030, more than 30 million people in the US are expected to have diabetes. (1,2)

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This is becoming a major issue in the mental healthcare community, since studies have suggested that patients treated with antipsychotic medications have a higher risk of diabetes than the general population. Yet as Leslie Citrome, MD, MPH, a professor of psychiatry at the New York University School of Medicine, explains below, the data on the possible connection between schizophrenia, antipsychotic selection, and diabetes are not clear-cut.

Seven percent of the American population has diabetes. (3) Research shows that patients with schizophrenia are at a higher risk of developing diabetes. Rates of type 2 diabetes mellitus in patients with schizophrenia are two to four times that in the general population. (4-7) In a recent report on the New York State Office of Mental Health psychiatric hospital system, the prevalence of patients with diabetes doubled from 6.9% of 10,091 patients in 1997 to 14.5% of 7,420 patients in 2004 irrespective of antipsychotic use. (8)

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Theories About the Schizophrenia-Diabetes Link

Several theories have been suggested to account for the apparent connection between diabetes and schizophrenia. One is the potential genetic link between the heritability of diabetes and the heritability of schizophrenia. Patients with schizophrenia have a higher rate of family history of diabetes than the general population. Studies have reported that 17 to 50% of people with schizophrenia have a family history of type 2 diabetes, (9,10) and a positive family history of diabetes may increase the risk of developing diabetes in individuals with schizophrenia and other serious and persistent mental illnesses up to threefold. (11)

We have known, even before the availability of antipsychotics, that patients with schizophrenia were prone to develop hyperglycemia. A link between schizophrenia and diabetes was postulated in the 1920s, (12) and a temporal association between first-generation antipsychotic drug treatment and hyperglycemia was first reported in the 1950s. (13)

Patients with schizophrenia often are disadvantaged economically, so they may not be able to afford healthier eating habits. These patients also may not be aware of the risks for diabetes or have access to adequate primary care services.

Large-scale epidemiologic studies (14,15) have spawned an increased interest in an association between second-generation antipsychotics and diabetes. Clinicians have begun to be more concerned about diabetes in patients with schizophrenia, because it has been suggested that the second-generation antipsychotics we are using today are putting our patients at a higher risk for developing diabetes.

Insulin resistance can take more than a decade to manifest as diabetes. Someone destined to become diabetic often has alterations in his or her ability to handle glucose that have existed for years--alterations that may remain asymptomatic in patients who remain unaware of having this problem until they eventually have their blood sugar levels checked. Thus, a patient with schizophrenia may have diabetes or prediabetes even before treatment with antipsychotics. Because of this and many other factors, the potential contribution of antipsychotic treatment toward the risk for developing diabetes mellitus is unclear. (14,15)

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