- Design
- Population-wide matched cohort study, administrative data (observational)
- Population
- 113,081 adults after a first TIA, mean age 70, Ontario 2002–2022
- Primary outcome
- Incident dementia at 1, 5 and 10 years
- Effect
- Dementia in 19.3%; HR 1.75 at 1 year, 1.34 overall vs controls
A population-wide Ontario cohort followed 113,081 people after a first TIA, matched to controls and to people with a first stroke, over a mean of about seven years.
Dementia was diagnosed in 19.3% after TIA, more often than in matched controls (2.71 vs 2.03 per 100 person-years). The excess risk was greatest in the first year (hazard ratio 1.75) and persisted for two decades (overall 1.34). Against stroke, the dementia risk after TIA was lower early (one-year hazard ratio 0.67) but converged to a similar level by five years, and dementia occurred far more often than recurrent stroke.
The message is to treat TIA as a long-term cognitive event, not only a warning of future stroke. Cognitive follow-up and aggressive vascular risk-factor control belong in the care plan, and a memory complaint after TIA deserves to be taken seriously rather than dismissed.
- Nearly one in five people developed dementia over about seven years after a TIA.
- Dementia risk was highest in the first year and stayed raised for two decades.
- By five years the dementia risk approached that seen after a full stroke.
- Build cognitive follow-up and vascular risk-factor control into post-TIA care.
Why it matters
It reframes TIA from a transient event to a marker of sustained cognitive risk that outlasts the stroke it warns of.
Don't overread it
This is observational: TIA and dementia share vascular risk factors, so the association does not prove the TIA itself caused the later cognitive decline.
The statistics, in plain English
A hazard ratio of 1.34 overall with tight intervals is a reliable association across a very large cohort, but matching and adjustment cannot remove every shared cause, so this is risk marking rather than proof of a causal chain.
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