Subsyndromal delirium is associated with poor functional outcome after ischaemic stroke

Background and purpose: Subsyndromal delirium (SSD) refers to patients with delirious symptoms who do not meet the criteria for delirium. The aim was to determine the prognostic significance of SSD in stroke patients.

Methods: In all, 564 patients with ischaemic stroke (median age 71 years, 50.5% female) were included. The Confusion Assessment Method was used to assess symptoms of delirium and the Diagnostic and Statistical Manual of Mental Disorders, 5th edn, criteria were used to diagnose delirium. SSD was defined as one or more core features of delirium without fulfilling diagnostic criteria. Functional outcome was assessed using the modified Rankin Scale at 3 and 12 months after stroke.

Results: Delirium was diagnosed in 23.4% of patients and SSD in 10.3% of patients. SSD was associated with increased risk of poor functional outcome. The adjusted odds ratios (ORs) for unfavourable outcome at 3 and 12 months were 2.88 [95% confidence interval (CI) 1.43-5.79, P < 0.01] and 2.93 (95% CI 1.39-6.22, P < 0.01), respectively. In multivariate analysis, delirium was an independent predictor of poor functional outcome at 3 months (OR 6.41, 95% CI 3.36-12.21, P < 0.01) and 12 months (OR 6.11, 95% CI 3.05-12.27, P < 0.01) after stroke. Delirium was also independently associated with increased risk of death within 3 months (hazard ratio 3.68, 95% CI 1.69-8.02, P < 0.01) and 12 months (hazard ratio 3.76, 95% CI 2.05-6.90, P < 0.01). SSD was not associated with increased risk of death.

Conclusions: In SSD patients the risk of poor functional outcome after stroke is increased and intermediate between patients with and patients without delirium.