Schizophrenia Patients at Risk for Developing Diabetes

A new meta analysis reported that patients with schizophrenia were at higher risk for developing type 2 diabetes, even when the study authors eliminated the effects of antipsychotic drugs, diet, and exercise.

Researchers searched three major databases for studies measuring glucose homeostasis in patients who had never before been treated with anti psychotic medications to examine whether individuals experiencing their first episode of schizophrenia already showed changes in their glucose levels when compared to control subjects.

The investigators ultimately discovered 14 case control studies which included 1,345 total participants and focused on fasting plasma glucose levels, plasma glucose levels after an oral glucose tolerance test, fasting plasma insulin levels, insulin resistance, and hemoglobin A1c levels in patients experiencing their first schizophrenic episode.

The researchers said that previous studies have established the idea that people with schizophrenia have their life expectancies shortened by between 15 and 30 years predominantly due to cardiovascular issues. However, type 2 diabetes was also estimated to be about 10 to 15% higher in schizophrenia patients than in the healthy population. The researchers attributed antipsychotic use to this association, but said that a relationship between schizophrenia and diabetes had already been observed as early as the 19^th century — before the introduction of antipsychotics.

The patients with schizophrenia demonstrated a higher risk for developing type 2 diabetes compared to the control subjects: they had higher levels of fasting blood glucose. Researchers added that the higher the glucose levels are in the blood, the higher odds the patient had diabetes.

Interestingly, the team noted that the patients who experienced their first schizophrenic episode had higher levels of insulin and increased levels of insulin resistance compared to the healthy controls.

The findings remained significant even after the researchers limited the studies to those where the patients and controls matched their diets, amount of regular exercise they received, and their ethnicities. By categorizing the results, the researchers were able to determine that the lifestyle factors or ethnicity could be ruled out as a predictor for diabetes, and could potentially highlight the ability of schizophrenia to have a direct link to increasing the risk of diabetes.

However, the investigators did note there were still risk factors that could increase the risk for developing both diseases — such as genetic risk and shared developmental risk factors like premature birth and low birth weight.

“Given that some antipsychotic drugs may increase the risk of diabetes further, clinicians have a responsibility to select an appropriate antipsychotic at an appropriate dose,” the study’s first author Toby Pillinger, MA, BA, BCh, MRCP said in a press release. “Our results also suggest that patients should be given better education regarding diet and physical exercise, monitoring, and, where appropriate, early lifestyle changes and treatments to combat the risk of diabetes.”

The study, titled “Impaired Glucose Homeostasis in First Episode Schizophrenia: A Systematic Review and Meta-analysis” was published in JAMA Psychiatry.

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