Prevalence of Severe Mental Illness and Its Associations With Health Outcomes in Patients With CKD: A Swedish Nationwide Study

Abstract

Rationale & Objective

Patients with chronic kidney disease (CKD) often face mental health problems, but the burden of severe mental illness (SMI) in this population is unclear. We estimated the prevalence of SMIs among people with CKD and their associations with health outcomes.

Study Design

Nationwide cross-sectional and cohort study.

Setting & Participants

Using the Swedish Renal Registry, we identified 32,943 patients with incident CKD G3b-5 or kidney replacement therapy (KRT) between 2008 and 2020 for estimation of the prevalence of SMIs. Data about the 30,103 patients not receiving KRT were used to examine associations between SMIs and subsequent health outcomes.

Exposure

Occurrence of SMIs (ie, schizophrenia, bipolar disorder, and major depressive disorder) before the date of first registration into the registry (index date), using diagnoses from inpatient or specialist outpatient care.

Outcome

30% decline in eGFR, initiation of KRT, and all-cause mortality.

Analytical Approach

Prevalence of SMIs was estimated in patients with CKD and compared with the general population using standardization with ratios adjusted for age, sex, and calendar year. Associations between SMIs and health outcomes were examined using Cox proportional hazards models.

Results

The overall prevalence of SMI was 7.3% in patients with CKD, which was 56% higher than the general population. The prevalences for schizophrenia, bipolar disorder, and major depressive disorder were 0.5%, 2.1%, and 5.6%, respectively. All 3 SMIs were associated with a higher mortality rate. Schizophrenia was not associated with 30% decline in eGFR (HR, 0.92 [95% CI, 0.65-1.29]), but it was associated with a lower rate of initiating KRT (HR, 0.56 [95% CI, 0.39-0.80]). Bipolar disorder was associated with a higher rate of 30% decline in eGFR (HR, 1.47 [95% CI, 1.29-1.67]) but a lower rate of initiating KRT (HR, 0.79 [95% CI, 0.67-0.94]). Major depressive disorder was not associated with 30% decline in eGFR or initiation of KRT.

Limitations

Lack of primary care data and exclusion of individuals with CKD G1-3a.

Conclusions

Patients with CKD had a higher prevalence of SMI compared with the general population. In patients with CKD, each SMI was associated with higher mortality, and bipolar disorder was associated with a faster eGFR decline. Patients with CKD and pre-existing schizophrenia or bipolar disorder experienced a lower rate of initiating KRT.

Plain-Language Summary

Patients with chronic kidney disease (CKD) frequently experience mental health problems, yet the prevalence and impact of severe mental illness (SMI) in this population remain uncertain. This Swedish nationwide study revealed that the prevalence of any SMI was 7.3% among patients with CKD (0.5% for schizophrenia, 2.1% for bipolar disorder, and 5.6% for major depressive disorder), representing a 56% higher prevalence than experienced by the Swedish general population. All 3 SMIs were associated with a higher mortality rate in patients with CKD, and bipolar disorder was also associated with a faster eGFR decline. Moreover, patients with CKD and schizophrenia or bipolar disorder exhibited a lower rate of initiating kidney replacement therapy. These findings highlight the need for improved recognition and management of SMI among people with kidney disease.