Among individuals with severe mental illnesses (SMI) such as schizophrenia and bipolar disorder, rates of comorbid medical conditions are higher than those found in the general population.1 The estimated prevalence of type 2 diabetes (T2D) in this patient group is 10% to 20%, and the onset of T2D occurs approximately 10 to 20 years earlier compared with patients with T2D without SMI.1

The risk for premature death is 3 to 4 times higher among patients with SMI and T2D compared with individuals with neither disease, and worse clinical outcomes have been observed in patients with T2D and SMI compared with those without SMI.1 In a 2011 study, for example, the risk for hospitalization for hypoglycemia or hyperglycemia was 74% higher among patients with T2D with vs without schizophrenia (hazard ratio, 1.74; 95% CI, 1.42-2.12).2

“The association between SMI and [T2D] is multifactorial, including lifestyle factors, possible side effects of antipsychotic medications, genetics, and the biological effects of SMI,” wrote the authors of a systematic review published in 2018 in Primary Care Diabetes.1

Several studies have demonstrated that patients with SMI receive suboptimal treatment for physical conditions such as diabetes.1 Experts have expressed concern that some aspects of the self-management model for T2D may not be practical for patients with SMI, who often face substantial challenges in terms of their living situation and available resources.

Food insecurity is one such issue that influences diabetes management. “If someone is food insecure, they often are unable to purchase foods that are healthy, and this impacts their management of diabetes,” explained Christina Mangurian, MD, MAS, a professor of clinical psychiatry at the University of California, San Francisco, in the School of Medicine. One of the aims of her National Institutes of Health-funded research program is to improve diabetes screening in patients with SMI. “Also, social isolation and lack of safe living environments might influence patients’ capacity to exercise — again, influencing their diabetes care,” she told Endocrinology Advisor.

Despite the clear need for improved management of T2D in patients with SMI, there is scant evidence regarding effective treatment strategies for this group. In a 2018 systematic review of studies regarding interventions to improve diabetes care in this population, only 7 of 1544 publications met inclusion criteria.1 The interventions examined included nutrition and exercise counseling, psychosocial treatment, diabetes education, and behavior modeling.

Collectively, these strategies were associated with minor improvements in several parameters, including glycated hemoglobin (HbA1c) levels (although nonsignificant), weight, fasting plasma glucose level, and diabetes knowledge. Common limitations of these studies included small sample sizes and lack of a similar control group.1

The authors of a 2017 meta-analysis also reported inadequate trial design as well as significant heterogeneity across studies on this topic.3 They examined 48 randomized controlled trials involving measurement of fasting blood glucose or HbA1c in patients with SMI (n = 4052) with or without diabetes, and found that pharmacologic and behavioral approaches reduced fasting glucose but not HbA1c. Subgroup analyses showed that use of metformin and antipsychotic switching strategies led to improvement in HbA1c, and the behavioral approaches with the greatest effect on fasting glucose were those that had a longer duration and included regular physical activity.

“While I definitely believe lifestyle approaches should be encouraged for people with SMI, I think that clinicians should treat these patients with evidence-based pharmacologic treatments such as metformin,” said Dr Mangurian. “Clinicians should also refer patients to locations where they can purchase low-cost healthy food options — and make sure they have the facilities to prepare these foods in their homes.”

Regarding diabetes self-management programs for patients with SMI, a 2016 Cochrane review found insufficient evidence on the topic.4 Only 1 controlled trial was identified, in which participants showed significant improvements in diabetes knowledge and body mass index, but not HbA1c, after participation in the 24-week Diabetes Awareness and Rehabilitation Training program.

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As described in a 2018 paper published in the Canadian Journal of Diabetes, Yuliya Knyahnytska, MD, MSc, MSW, PhD, and colleagues at the University of Toronto conducted a critical ethnography to explore the personal experiences of people with co-occurring diabetes and SMI.5 The researchers noted the need for a “shift toward social and contextual understandings of the lived realities of patients,” which may ultimately inform the development of patient-oriented practices and public health strategies.

To explore the topic in depth, Endocrinology Advisor interviewed Dr Knyahnytska as well as Najma Siddiqi, MBChB, MRCP, MRCPsych, PhD, clinical senior lecturer in psychiatry and coauthor of the 2017 meta-analysis mentioned above.3