PREDICTING EPILEPSY AND SEIZURES FROM VASCULAR RISK FACTORS AMONG ELDERLY PATIENTS [P09.061]

Amir M. Arain, Pradumna Singh, Yanna Song, Lily Wang, Van Cain, Zahid Samad, Baqar Husaini, Nashville, TN

Epidemiologic studies have demonstrated that the incidence of new-onset epilepsy or other seizure disorders increases markedly in the elderly. There are many causes, but stroke accounts for 30% to 40% of all cases.^1-3 Healthy subjects without a history of stroke, head injury, or dementia appear to have a lower risk of epilepsy.⁴ Although cerebrovascular disease is known to cause seizures in many older patients, there is little information about how the presence of vascular disease risk factors in seizure-free elderly individuals predicts the subsequent development of seizures.

It would be important to understand these risk factors and their development in order to possibly modify them and prevent the development of epilepsy. In this poster, Arain et al examined the effects of depression and several vascular risk factors in seizure-free elderly subjects on the subsequent incidence of epilepsy over a 6-year period. The investigators identified elderly individuals from a large database of physician Medicare reimbursement records, and screened out those who had seizures at baseline. Beginning in 1996, the investigators identified 5 baseline patient cohorts: 65 to 69 years old (n = 190 585), 70 to 74 years old (n = 170 548), 75 to 79 years old (n = 122 614), 80 to 84 years old (n = 80 494), and 85 years old or older (n = 60 556). The incidence of new seizure diagnoses was examined for each cohort over the 6-year period from 1997 to 2002. In addition, the investigators calculated the odds ratio for developing a seizure disorder as a function of baseline values of 7 risk factors in 1996 at baseline: diabetes, hypercholesterolemia, hypertension, myocardial infarction, heart failure, stroke, and depression.

Over the 6-year study period, patients who were older at baseline were more likely to develop new-onset seizure disorders. For example, seizures occurred in 2.79% of patients who were 65 to 69 years of age at baseline, compared with 4.13% for patients who were 80 to 84 years old, or 3.58% for patients over the age of 85. The rates of several seizure risk factors also increased with age, especially diabetes, hypertension, congestive heart failure, depression, and stroke. Examination of seizure risk factors for the different age cohorts revealed that stroke in 1996 was associated with a significantly elevated risk of seizures between 1997 and 2002 for all 5 age cohorts. The odds ratio of developing seizures for individuals with stroke at baseline was highest for the youngest cohort (2.35) and decreased with age (to 1.50 for patients who were 80 to 84 years old at baseline and 1.29 for patients over 85). Depression and hypercholesterolemia were significant predictors of seizures for patients between the ages of 65 and 84, but not for the oldest patients; and diabetes and congestive heart failure were significant predictors of seizures for patients between the ages of 65 and 79. Hypertension was significantly associated with seizure risk only in patients over the age of 85, and myocardial infarction was predictive of future seizures only in those between ages 75 and 79 at baseline.

The presenters concluded that although several important vascular risk factors increase the risk of seizures among elderly patients, many of these risk factors are potentially modifiable. Interventions to prevent or manage stroke, hypertension, diabetes, and congestive heart failure may be especially important for reducing seizure risk among older patients. Depression is a predictor of future seizures among the elderly, but may also be caused by seizure disorders. In either case, the presenters emphasized the importance of treating depression in elderly patients to improve overall quality of life.

References
1. Cloyd J, Hauser W, Towne A, et al.Epidemiological and medical aspects of epilepsy in the elderly. Epilepsy Res. 2006;68(Suppl 1):S39-S48.
2. Leppik IE. Epilepsy in the elderly: scope of the problem. Int Rev Neurobiol. 2007;81:1-14.
3. De Reuck J, Goethals M, Vonck K, Van Maele G. Clinical predictors of late-onset seizures and epilepsy in patients with cerebrovascular disease. Eur Neurol. 2005;54:68-72.
4. Hussain SA, Haut SR, Lipton RB, Derby C, Markowitz SY, Shinnar S. Incidence of epilepsy in a racially diverse, community-dwelling, elderly cohort: results from the Einstein aging study. Epilepsy Res. 2006;71:195-205.