Objective To investigate whether poststroke dementia (PSD) diagnosed after ischaemic stroke predicts recurrent ischaemic stroke in long-term follow-up.

Methods We included 486 consecutive patients with ischaemic stroke (388 with first-ever stroke) admitted to Helsinki University Central Hospital who were followed-up for 12 years. Dementia was diagnosed in 115 patients using the Diagnostic and Statistical Manual of Mental Disorders, 3rd edition (DSM-III) criteria. The effects of risk factors and  PSD on survival free of recurrent stroke were estimated using Kaplan–Meier log-rank analyses, and the HRs for stroke recurrence were calculated using Cox proportional hazards models.

Results In the entire cohort, patients with PSD had a shorter mean time to recurrent stroke (7.13 years, 95% CI 6.20 to 8.06) than patients without dementia (9.41 years, 8.89 to 9.92; log rank p<0.001). This finding was replicated in patients with first-ever stroke (6.89 years, 5.85 to 7.93 vs 9.68 years, 9.12 to 10.24; p<0.001). In Cox univariate analysis, PSD was associated with increased risk for recurrent stroke both in the entire cohort (HR 2.02; 95% CI 1.47 to 2.77) and in those with first-ever stroke (2.40; 1.68 to 3.42). After adjustment for the significant covariates of age, atrial fibrillation, peripheral arterial disease and hypertension, PSD was associated with increased risk for recurrent stroke both in the entire cohort (1.84; 1.34 to 2.54) and in those with first-ever stroke (2.16; 1.51 to 3.10).

Conclusions Poststroke dementia predicts recurrence of ischaemic stroke in long-term follow-up and should be considered when estimating prognosis.