Neuropsychiatric Symptoms of Epilepsy

14 Dementia
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investigations that noted a significantly higher incidence of seizures in Alzheimer’s
disease patients than in elderly controls without dementia [ 13 , 14 ]. The incidence of
unprovoked seizures is clearly higher in sporadic AD than in the reference population,
and the increase appears to be independent of disease stage [ 16 , 39 ].
In patients with Alzheimer’s disease, approximately 10–22 % had at least one
unprovoked seizure [ 40 ]. Relative risk estimates vary considerably between studies,
ranging from a sixfold higher risk in one study [ 15 ] to a tenfold higher risk in
another study [ 13 ], depending on whether patients with AD were recruited from a
special care facility or from a population-based setting. Also there is considerable
variability in the reported lifetime prevalence rates of 1.5–64 % [ 41 ].
Interestingly, Scarmeas et al. [ 17 ] even reported that unprovoked seizures are not
common in AD, as only about 1.5 % of patients with AD developed seizures over
the course of a mean of 3.7 years of follow-up; still seizures do occur more frequently
than in the general population.
The associations between seizures and the age of onset/stage/severity of AD are
also the matter of controversy.
Advanced Alzheimer’s disease is often considered a risk factor for new-onset
generalized tonic–clonic seizures in older adults; it is associated with a 10 % prevalence
of seizures, particularly late in the illness [ 14 ]. Indeed, the increasing age is a
common and well-established risk factor for both epilepsy and AD [ 42 ]. Mendez
and Lim also noted that seizures usually occur in later stages of Alzheimer’s disease,
on average ≥6 years of the disease [ 40 ]. In the huge follow-up study with a
nested case–control analysis using the United Kingdom–based General Practice
Research Database (GPRD), Imfeld et al. demonstrated that the patients with longer
standing (more than 3 years) AD had a higher risk of developing seizures or epilepsy
than those with a shorter duration of disease, although this difference was not
statistically significant [ 43 ].
However, a number of studies reported higher incidence of seizures in early AD
[ 44 ]. In these studies, the highest risk was detected among younger persons with
early-onset dementia (50–60 years), an age when their general incidence in the population
remains low. It was demonstrated that the relative risk of unprovoked seizures
markedly increases in patients with early-onset AD, reaching 3-, 20-, and
87-fold with dementia onset when aged 70–79, 60–69, or 50–59 years, respectively
[ 16 ]. Also it has been noted that more than 80 % pedigrees of patients with very
early onset of dementia (