Elsevier

Epilepsy Research

Volume 107, Issue 3, December 2013, Pages 306-310
Epilepsy Research

Racial and ethnic differences in epilepsy classification among probands in the Epilepsy Phenome/Genome Project (EPGP)

https://doi.org/10.1016/j.eplepsyres.2013.09.007Get rights and content

Highlights

  • Friedman; racial and ethnic differences in epilepsy classification among probands in the Epilepsy Genome/Phenome Project (EPGP).

  • We examined racial/ethnic groups in subjects with non-acquired epilepsy enriched for a genetic cause.

  • The majority (77.2%) of subjects were exclusively Caucasian/white.

  • Generalized epilepsies were more common among Caucasians than among those with African ancestry.

  • Subjects with African ancestry were more likely to have unclassifiable syndromes.

  • This was most often due to incomplete or conflicting diagnostic tests.

Summary

Little is known about the ethnic and racial differences in the prevalence of generalized and focal epilepsy among patients with non-acquired epilepsies. In this study, we examined epilepsy classification and race/ethnicity in 813 probands from sibling or parent–child pairs with epilepsy enrolled in the Epilepsy Genome/Phenome Project (EPGP). Subjects were classified as generalized epilepsy (GE), non-acquired focal epilepsy (NAFE), mixed epilepsy syndrome (both generalized and focal), and unclassifiable, based on consensus review of semiology and available clinical, electrophysiology, and neuroimaging data. In this cohort, 628 (77.2%) subjects identified exclusively as Caucasian/white and 65 (8.0%) subjects reported African ancestry, including subjects of mixed-race. Of the Caucasian/white subjects, 357 (56.8%) had GE, 207 (33.0%) had NAFE, 32 (5.1%) had a mixed syndrome, and 32 (5.1%) were unclassifiable. Among subjects of African ancestry, 28 (43.1%) had GE, 27 (41.5%) had NAFE, 2 (3.1%) had a mixed syndrome, and 8 (12.3%) were unclassifiable. There was a higher proportion of subjects with GE compared to other syndromes among Caucasians/whites compared to subjects with African ancestry (OR 1.74, 95% CI: 1.04–2.92, two-tailed Fisher's exact test, p = 0.036). There was no difference in the rate of GE among subjects reporting Hispanic ethnicity (7.6% of total) when adjusted for race (Caucasian/white vs non-Caucasian/white; OR 0.65, 95% CI: 0.40–1.06, p > 0.05). The proportion of participants with unclassifiable epilepsy was significantly greater in those of African-American descent. In a group of patients with epilepsy of unknown etiology and an affected first degree relative, GE is more common among Caucasian/white subjects than among those with African ancestry. These findings suggest there may be geographical differences in the distribution of epilepsy susceptibility genes and an effect of genetic background on epilepsy phenotype. However, the results should be interpreted with caution because of the low numbers of African-Americans in this cohort and more limited diagnostic data available for epilepsy classification in these subjects compared to Caucasians/whites.

Introduction

Little is known about the distribution of epilepsy susceptibility genes and epilepsy syndromes among racial and ethnic groups. The photo-paroxysmal response (PPR), an electroencephalographic finding associated with idiopathic generalized epilepsy (GE), is more common among people of European ancestry than among those of African ancestry (Adamolekun et al., 1998, de Graaf et al., 1995) suggesting there may be variability in the prevalence of epilepsy syndromes among people of different ancestries. We examined the relationship between self-reported race and ethnicity and epilepsy type in a large cohort of individuals with epilepsy of unknown cause. Based on the distribution of the PPR, we hypothesized that GEs would be less common in subjects of African ancestry than Caucasians/whites.

Section snippets

Subjects

We examined epilepsy classification and race/ethnicity in 813 probands from sibling or parent–child pairs with epilepsy enrolled in the Epilepsy Phenome/Genome Project (EPGP), a multi-center, collaborative effort to collect detailed phenotypic and genetic data on a 3750 patients with epilepsy (Nesbitt et al., 2013, The EPGP Collaborative, 2013). Subjects were enrolled at 27 sites, all but four (Argentina, Australia, Canada and New Zealand) of which were in the United States. Subjects were

Results

The distribution of ILAE epilepsy syndromes among the 813 probands is shown in Table 1. Because the low frequency of many specific syndromes among the probands precluded analysis of racial and ethnic differences within them, further analysis was restricted to the broad classification categories of GE, NAFE, mixed syndrome and unknown. The racial and ethnic categories of the subjects along with their epilepsy syndrome classification are shown in Table 2. Of the 813 probands, 628 (77.2%)

Discussion

In this cohort of patients, enriched for genetic contributions to their epilepsy by virtue of having a family history of first-degree relatives with non-acquired epilepsy, GE was more common in whites than in those with self-reported African ancestry, suggesting there may be racial differences in the prevalence of epilepsy syndromes. These results should be interpreted with caution due to the low number of subjects with African ancestry in this cohort and the higher proportion of unclassified

Disclosures

Dr. Friedman receives salary support from The Epilepsy Study Consortium, a non-profit organization dedicated to improving the lives of epilepsy patients, and devotes 15% of his time to work done for the Consortium. The Consortium receives payments from a large number of pharmaceutical companies for consulting activities. All payments are made to The Consortium and not to Dr. Friedman directly. Several companies also support the Consortium's biennial Antiepileptic Drug Trials Symposium. Since

Acknowledgments

Supported by NINDS U01 NS 053998. We would like to acknowledge the recruitment contributions of the EPGP Community Referral Network (CRN). The CRN consists of healthcare professionals not paid by the EPGP grant who refer eligible families to EPGP. A list of individual contributors can be found at www.epgp.org. In addition, we would like to acknowledge the efforts of the clinical coordinators, the site principal investigators, neurologists, and support staff at our EPGP clinical centers who have

References (12)

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