Comparisons of the clinical outcomes between early- and adult-onset bipolar disorders: A prospective cohort analysis

Abstract

Background: This study aimed to explore the impact of age-at-onset on clinical outcomes in bipolar-spectrum disorders, including the development of alcohol or substance use disorder, suicidality, and psychiatric hospitalization.

Methods: This population-based study enrolled newly-diagnosed bipolar-spectrum patients, including 4,367 patients with early-onset bipolar disorder (EOBD), 64,787 patients with adult-onset bipolar disorder (AOBD), and the same number of age-controlled comparison subjects without bipolar disorder, from Taiwan's National Health Insurance Research Database. Time-dependent covariate Cox regression models were used to estimate the effect of age-at-onset on clinical outcomes with adjustment for pre-existing psychiatric comorbid conditions and pharmacological treatment patterns. Sensitivity analyses using different definitions of study sample and age cutoffs were conducted.

Results: The average follow-up duration was 5.7 years. After adjustment with time-dependent covariates and chronological age, there were no significant differences in the risks for developing new-onset alcohol or substance use disorders and psychiatric hospitalization between EOBD and AOBD patients. Although EOBD patients had a higher risk of hospitalization for suicide and self-harm than did AOBD patients in primary analysis, this finding did not replicated in the sensitivity analyses.

Limitations: The symptom profile and severity of bipolar disorder was not available in the NHIRD; therefore, surrogate indicators of clinical outcome might not be sensitive enough to detect the subtle differences.

Conclusions: EOBD and AOBD patients had similar risks for developing alcohol or substance use disorders. Their risk of psychiatric hospitalization was similar. Whether EOBD patients might have a higher risk of hospitalization for suicide and self-harm warrants further investigations.

Keywords: Clinical outcomes; Early-onset bipolar disorders; Hospitalization; Self-harm; Substance use disorder.