Long-Term Risk of Dementia After TIA: A Population-Wide Matched Cohort Study.
Long-term risk of dementia after TIA remains poorly characterized, despite a known impact on cognition. We aimed to quantify the rate, relative risk, and time course of incident dementia after TIA compared with a matched reference population (controls) and individuals with stroke.
We conducted a population-wide cohort study using linked administrative health data for the province of Ontario, Canada (2002-2022). Adults with a first TIA were identified from emergency department visits or hospital admissions and followed from 90 days after the index event. Individuals with prior dementia, prior stroke, early death, or long-term care admission were excluded. Patients with TIA were matched to population controls on age, sex, neighborhood-level deprivation, rurality, and vascular comorbidities. Patients with TIA were also matched to those with first stroke. Incident dementia was ascertained using a validated algorithm based on hospital diagnoses, physician claims, and dementia-specific medications. Cause-specific and subdistribution hazard models accounting for competing risk of death were used for 1-, 5-, and 10-year risk of dementia, with time-varying analyses.
Among 113,081 matched patients with TIA (mean age 70 years; 50% female), dementia was diagnosed in 19.3% over a mean follow-up of 7.11 years (SD 5.16). Dementia rates after TIA were consistently higher than in matched controls across all time horizons (overall rate 2.71 vs 2.03 per 100 person-years). The hazard ratio for dementia after TIA was highest within the first year (hazard ratio [HR] 1.75, 95% CI 1.66-1.85) and remained elevated over 20 years of follow-up (overall HR 1.34, 95% CI 1.31-1.36). Compared with stroke, the hazard of dementia was lower after TIA early on (1-year HR 0.67, 95% CI 0.64-0.70) but converged and became similar after 5 years of follow-up. Dementia incidence substantially exceeded stroke incidence, and adjustment for incident stroke minimally attenuated results.
TIA is associated with a large and sustained increase in dementia risk, approaching that observed after stroke over long-term follow-up. Dementia occurs far more frequently than incident stroke after TIA, highlighting cognitive decline as a major long-term complication and a target for prevention with new strategies that include and extend beyond stroke prevention.
We conducted a population-wide cohort study using linked administrative health data for the province of Ontario, Canada (2002-2022). Adults with a first TIA were identified from emergency department visits or hospital admissions and followed from 90 days after the index event. Individuals with prior dementia, prior stroke, early death, or long-term care admission were excluded. Patients with TIA were matched to population controls on age, sex, neighborhood-level deprivation, rurality, and vascular comorbidities. Patients with TIA were also matched to those with first stroke. Incident dementia was ascertained using a validated algorithm based on hospital diagnoses, physician claims, and dementia-specific medications. Cause-specific and subdistribution hazard models accounting for competing risk of death were used for 1-, 5-, and 10-year risk of dementia, with time-varying analyses.
Among 113,081 matched patients with TIA (mean age 70 years; 50% female), dementia was diagnosed in 19.3% over a mean follow-up of 7.11 years (SD 5.16). Dementia rates after TIA were consistently higher than in matched controls across all time horizons (overall rate 2.71 vs 2.03 per 100 person-years). The hazard ratio for dementia after TIA was highest within the first year (hazard ratio [HR] 1.75, 95% CI 1.66-1.85) and remained elevated over 20 years of follow-up (overall HR 1.34, 95% CI 1.31-1.36). Compared with stroke, the hazard of dementia was lower after TIA early on (1-year HR 0.67, 95% CI 0.64-0.70) but converged and became similar after 5 years of follow-up. Dementia incidence substantially exceeded stroke incidence, and adjustment for incident stroke minimally attenuated results.
TIA is associated with a large and sustained increase in dementia risk, approaching that observed after stroke over long-term follow-up. Dementia occurs far more frequently than incident stroke after TIA, highlighting cognitive decline as a major long-term complication and a target for prevention with new strategies that include and extend beyond stroke prevention.
Authors
Joundi Joundi, Fang Fang, Austin Austin, Smith Smith, Yu Yu, Hachinski Hachinski, Sposato Sposato, Ganesh Ganesh, Sharma Sharma, Kapral Kapral
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