Plasma Insulin Level Correlation to Metabolic Parameter Shifts in Hospitalized Psychiatric Patients

Objective To identify potential correlations between baseline plasma insulin level and shifts in metabolic status in psychiatric inpatients. Methods A population of 75 patients was identified for this single-center, retrospective study conducted at a state psychiatric hospital in Kansas City, Missouri. Patients were selected on the basis of presence of a baseline fasting plasma insulin level drawn at admission; duration of stay ≥ 12 weeks between August 1, 2013, and December 31, 2015; and presence of metabolic laboratory and weight measurements at baseline and 3 months. Total initial plasma insulin level (≥ 19 µIU/mL or < 19 µIU/mL) was compared to shifts in metabolic laboratory measurements and weight. A secondary analysis was performed to detect association between the numerical values of assessed parameters and the numerical values for plasma insulin measurements. Results The primary analysis found no correlation between plasma insulin level and changes in any metabolic parameter category at 3 (n = 75) or 6 months (n = 30) after admission. Secondary analysis found significant correlations between the numerical values of baseline total plasma insulin level and fasting plasma glucose level at baseline (r = 0.492, P < .001), 3 months (r = 0.247, P = .035), and 6 months (r = 0.723, P < .001). Secondary analysis demonstrated a significant correlation between baseline total plasma insulin level and hemoglobin A1c values at baseline (r = 0.329, P = .004), 3 months (r = 0.455, P < .001), and 6 months (r = 0.517, P = .003). Conclusions Baseline total plasma insulin levels were strongly correlated with parameters affected directly by alterations in glucose up to 6 months after admission but were weakly correlated or not correlated with other metabolic parameters. The results do not support routine use of plasma insulin as a predictor for shifts in metabolic parameters in patients receiving antipsychotic medications.