Epilepsy and dementia have a bidirectional relationship. Dementia can increase the risk of seizures and epilepsy, while late-onset epilepsy is associated in population studies with an increased later risk of cognitive decline and dementia.
The relationship runs in both directions
Systematic reviews and longitudinal studies consistently find that people with dementia have a higher risk of developing seizures or epilepsy than people without dementia.
Conversely, people with epilepsy—particularly unexplained late-onset epilepsy—have higher rates of later dementia than comparable populations without epilepsy. These associations do not prove that one condition always causes the other.
Alzheimer’s disease and network hyperexcitability
Alzheimer’s disease is increasingly understood to involve abnormal network excitability as well as progressive neurodegeneration.
Amyloid and tau pathology, interneuron dysfunction and hippocampal network changes may contribute to epileptiform activity in some people.
Seizures can be subtle
Seizures in dementia are often focal and can present as brief staring, speech arrest, amnesia, sensory symptoms or behavioural arrest rather than convulsions.
These events can be mistaken for fluctuations in cognition, delirium, syncope or progression of the dementia itself.
EEG may need to go beyond a routine recording
Epileptiform abnormalities in Alzheimer’s disease can be intermittent and may be more common during sleep.
A normal short routine EEG therefore does not exclude epilepsy. Longer or sleep-containing recordings can sometimes be useful when suspicion remains high.
Early-onset Alzheimer’s carries particular seizure risk
Research suggests that seizure risk is particularly increased in younger-onset Alzheimer’s disease and in more advanced disease.
The exact prevalence varies substantially between studies because definitions and methods differ.
Treatment must protect cognition as well as control seizures
Older adults and people with dementia can be more vulnerable to sedation, imbalance, behavioural effects and drug interactions.
Antiseizure medication choice therefore needs to account for cognition, mood, falls, kidney and liver function, other medicines and the seizure type.
Late-onset epilepsy can be a clue, not a diagnosis of dementia
New epilepsy in later life should prompt assessment for common causes such as stroke, tumour and neurodegenerative disease, but most people with late-onset epilepsy should not be told that dementia is inevitable.
The relationship is probabilistic and heterogeneous.
An active research frontier
Researchers are studying whether treating subclinical epileptiform activity could alter cognitive trajectories in selected people with Alzheimer’s disease.
At present, this remains an evolving research area rather than established dementia treatment.
Related reading
Sources and further reading
- Epilepsy and dementia systematic review and meta-analysis, 2024
- Bidirectional associations of epilepsy with dementia and Alzheimer’s disease
- Epilepsy and epileptiform activity in late-onset Alzheimer disease, 2024 review
- Bidirectional relationship between epilepsy and Alzheimer’s disease, 2025
Evidence checked: September 2026.