Study finds bidirectional relationship between diabetes complications and mental illness

A new study from Michigan Medicine and the University of Michigan School of Public Health further sheds light on the relationship between diabetes complications and mental illness, with results suggesting the relationship runs in both directions.¹

“We wanted to know whether chronic diabetes complications lead to psychiatric illness or whether psychiatric illness leads to diabetic complications, and we found that both associations are true,” said senior investigator Brian Callahan, MD, MSc, and Eva L. Feldman, MD, professor of neurology at the University of Michigan Medicine.² “The findings highlight the need for clinicians to proactively screen for mental health problems in their diabetic patients, in addition to screening for chronic complications, which is recommended as standard of care for people with diabetes.”

Citing interest in further exploring the relationship between mental illness and chronic diabetes complications, Callaghan and colleagues designed the current study as an analysis of insurance claims data from the Optum Clinformatics Data Mart Database from 2001 to 2018. The researchers used ICD-9 and -10 codes to identify 44,735 individuals with type 1 diabetes and 152,187 individuals with type 2 diabetes for inclusion in the study. They used common reference group propensity scoring to match individuals with type 1 diabetes to individuals with type 2 diabetes and individuals without diabetes. Matching was stratified by age group, and propensity scores were calculated using age at study entry, sex, race/ethnicity, geographic region, education level, net worth, insurance plan type, high-deductible health plan status, modified Charlson comorbidity index, year of enrollment, and follow-up period.¹

In total, 356,630 patients without diabetes were identified for the study. The researchers noted that personal characteristics were closely matched across the three groups. They also noted that the proportions of female participants were 47.5%, 46.0%, and 51.8% in the type 1, type 2, and non-diabetic groups, respectively, and the majority in each group were white, 74.1%, 76.5%, and 76.7%, respectively.¹

For their analysis, the researchers fitted time-varying Cox proportional hazards models of diagnoses of chronic diabetic complications or psychiatric disorders to examine their association with the development of psychiatric disorders or chronic diabetic complications, respectively. Psychiatric disorders included in this study included anxiety and depression. Chronic diabetic complications included in this study included neuropathy, retinopathy, nephropathy or diabetic kidney disease, stroke, myocardial infarction, peripheral vascular disease, and amputation.¹

The analysis showed that having chronic diabetes complications almost doubled or more the risk of developing mental disorders, with the highest risk observed in the oldest old age groups.¹

• Age 0-19 years: HR, 2.1; 95% CI, 1.4-3.2
• Age 20-39 years: HR, 1.9; 95% CI, 1.6-2.4
• 40-59 years: HR, 2.1, 95% CI, 1.8-2.5
• Age 60 years or older: HR 2.9; 95% CI, 2.4–3.4

When assessing risk of chronic diabetes and psychiatric comorbidities, risk was significantly increased in all groups, but the magnitude of the effect decreased from age 0 to 19 years (HR, 2.5; 95% CI, 1.7 to 3.7) to age 20 to 39 years (HR, 1.5; 95% CI, 1.2 to 2.9) but remained relatively stable up to age 40 to 59 years (HR, 1.4; 95% CI, 1.2 to 1.7) and age 60 years or older (HR, 1.6; 95% CI, 1.3 to 1.8).¹

Further analysis revealed that, among those under age 60, people with type 1 diabetes were more likely to have chronic diabetic complications and people with type 2 diabetes were more likely to have mental illness. However, the researchers noted that the relationship between chronic diabetic complications and mental illness was not affected by type of diabetes in either direction (P > .05 for interaction effect).¹

“It's likely a combination of direct and indirect effects and shared risk factors that are driving the associations we're seeing,” said lead researcher Maya Watanabe, MD, PhD, a biostatistician at the Harvard School of Public Health and a former graduate research assistant at the University of Michigan.² “By offering interventions to treat these common risk factors, diabetes care providers may be able to prevent the risk of multiple complications simultaneously.”

References:

1. Watanabe M, Reynolds EL, Banerjee M, et al. “Bidirectional associations between psychiatric disorders and chronic diabetic complications in patients with type 1 or type 2 diabetes.” Diabetes CarePublished online July 15, 2024. doi:10.2337/dc24-0818
2. Michigan Medicine. Study finds mental health and chronic diabetes complications strongly linked in both directions. Michigan Medicine. August 22, 2024. Accessed August 26, 2024. https://www.michiganmedicine.org/health-lab/mental-health-and-chronic-diabetes-complications-strongly-linked-both-ways-study-finds.