Psychiatric Multimorbidity and Risk of Dementia: A 23-Year Cohort Study Using Akrivia Health Secondary Mental Healthcare Data

OBJECTIVES: Psychiatric disorders in adulthood have been found to independently increase the risk of dementia in later life. However, the impact of psychiatric multimorbidity (the co-occurrence of two or more disorders) on dementia risk remains unclear. This study aims to investigate whether patients with psychiatric multimorbidity are at higher risk of dementia compared to those diagnosed with a single disorder of anxiety, major depressive disorder (MDD), schizophrenia or bipolar disorder.

METHODS: Using Akrivia Health’s secondary mental healthcare database, which holds electronic health records for 4.6 million patients in the UK, we analysed 118,271 patients diagnosed with psychiatric disorders, including MDD, bipolar disorder, schizophrenia, and anxiety disorders. Patients were included if they had a recorded diagnosis from 2000 to 2024, were aged 40 or over at their first recording of psychiatric diagnosis and remained dementia-free for two years post-diagnosis. Patients were grouped based on their diagnosis, with anxiety disorders used as the reference group, and those with more than one diagnosis classified into a separate 'multimorbidity' group. Cox proportional hazards regression models were used to estimate hazard ratios (HR) for the associations between patient groups and dementia incidence, adjusted for age, gender, and ethnicity.

RESULTS: A total of 12,628 individuals developed dementia during follow-up. Psychiatric multimorbidity was significantly associated with the highest risk of dementia (HR=2.81, 95% confidence interval [CI] 2.62−3.01), followed by MDD (HR=1.25, 95% CI 1.17−1.33), schizophrenia (HR=1.28, 95% CI 1.18−1.38) and bipolar disorder (HR=1.17, 95% CI 1.07−1.27), when compared to the anxiety disorders group.

CONCLUSIONS: This study showed that psychiatric multimorbidity significantly increases a person's risk for developing dementia beyond that associated with having a single psychiatric disorder alone. This suggests that early identification of individuals at risk of accumulating multimorbidity, and tailored interventions to prevent or delay the onset of such multimorbidity, might mitigate dementia risk.