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New Data on Epilepsy Prevalence — Higher Numbers on Federal and State Levels

Moran, Mark

doi: 10.1097/01.NT.0000525668.20141.73
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ARTICLE IN BRIEF

A new federal analysis found that the number of persons with active epilepsy increased compared with earlier years. The study authors hope that the estimates spur more states to engage in active surveillance of the condition.

Approximately three million US adults and 470, 000 children were living with active epilepsy in 2015, according to new statistics from the Centers for Disease Control and Prevention (CDC) reported in the August 11 Morbidity and Mortality Weekly Report.

State level estimates, based on statistical modelling, suggest a range from 5,900 persons with epilepsy in Wyoming to more than 427,000 in California. However, prevalence rates — based on the statistical modelling accounting for variability in age and income — appear to be roughly equal across the states, according to the CDC report. Observed estimates of prevalence are lacking for all 50 states.

The number of persons with active epilepsy increased compared with earlier years, likely because of population growth.

“This study provides updated national and modeled state-specific numbers of active epilepsy cases,” wrote the co-authors from the Division of Population Health at CDC. “Public health practitioners, health care providers, policy makers, epilepsy researchers, and other epilepsy stakeholders, including family members and people with epilepsy, can use these findings to ensure that evidence-based programs meet the complex needs of adults and children with epilepsy and reduce the disparities resulting from it.”

“This study provides updated national and modeled state-specific numbers of active epilepsy cases,” wrote co-authors Rosemarie Kobau, MPH, and Matthew Zack, MD, in the division of population health at the CDC. “Public health practitioners, health care providers, policy makers, epilepsy researchers, and other epilepsy stakeholders, including family members and people with epilepsy, can use these findings to ensure that evidence-based programs meet the complex needs of adults and children with epilepsy and reduce the disparities resulting from it.”

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STUDY DESIGN

For the survey, CDC used the 2015 National Health Interview Survey (NHIS) for adults (aged ≥18 years), the 2011-2012 National Survey of Children's Health (NSCH), and the 2015 Current Population Survey data, to estimate prevalent cases of active epilepsy, overall and by state.

Importantly, the data sources relied on patient self-reports for adults: Individuals were classified as having active epilepsy if they reported a history of doctor-diagnosed epilepsy and were taking medication to control it, had had one or more seizures in the past year, or both. For children, the NSCH asked parents or guardians if a doctor or health care provider ever told them that their child had epilepsy or seizure disorder, and if so, if their child currently has epilepsy or seizure disorder.

For the state level estimates, the research team used NHIS and NSCH data to calculate the prevalence of active epilepsy for three age groups (0-17 years, 18-64 years, and ≥65 years) stratified by three family income groups (0-99 percent, 100-199 percent, ≥200 percent of poverty thresholds). They obtained data for the three age groups and three family income groups for each state from the US Census's Current Population Survey 2015 Annual Social and Economic Supplement. Multiplying the age- and income-specific active epilepsy prevalence estimates by the population estimates for each of the three age and income groups yielded state-level estimates of active epilepsy, indirectly standardized for age and income.

The data indicate that 1.2 percent of the US population (3.4 million persons, including three million adults and 470,000 children) reported active epilepsy. Among children, the estimated number of cases of current epilepsy ranged from 800 in Wyoming to 59,800 in California.

The number of adults and children estimated to have active epilepsy was less than 14,000 in nine states and the District of Columbia, 14,000-32,799 in 11 states, 32,800-56,799 in nine states, 56,800-92,699 in 10 states, and greater than 92,700 persons in 11 states. The prevalence of epilepsy, or proportion of the population with active disease, was the same for each age group and income group across states, according to the report.

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In an interview with Neurology Today, Kobau and Dr. Zack emphasized that prior to 2010, epilepsy prevalence was surveyed only intermittently: The last US national estimate of epilepsy prevalence was based on 1986-1990 data using one question assessing the occurrence of epilepsy or repeated seizures, convulsions, or blackouts in any household family members.

Especially important and new, they said, are the state-level estimates. “We think it's important for state officials to make sure health and social service providers have an accurate sense of the prevalence of the condition to address gaps in epilepsy care,” Kobau said. “It would be preferable to have observed estimates of prevalence. We hope this [analysis] prompts stakeholders in the field — physicians, health systems and patient advocates — to work with state and federal officials to expand epilepsy surveillance and gather better data.”

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EXPERT COMMENTARY

Nathalie Jette, MD, MSc, FRCPC, chief of neurology research at the Icahn School of Medicine at Mount Sinai, said the report is “a carefully designed study, where the authors used a validated case definition to obtain self-reported estimates of epilepsy across the nation. The CDC is to be congratulated for having undertaken this important study that will help guide public policy and resource allocation for those living with epilepsy nationally.”

But she noted the limitation inherent in using self-reported data and echoed the authors' call for better, observed state level data. “To really appreciate the variability from state to state, one would need to see prevalence estimates for each state adjusted at the very least for age, sex and the overall population,” she said.

W. Allen Hauser, MD, FAAN, special lecturer in the Gertrude H. Sergievsky Center and retired professor of neurology and epidemiology at Columbia University, said the statistics indicate a higher prevalence than that found in a 2012 Institute of Medicine report (which reported a total of 2.2 million adults) and will be useful for state and federal advocacy for treatment and research. From a scientific perspective, Dr. Hauser said, the most important finding is the rough equivalence in prevalence across states.

He too noted the need for observed data at the state level, and said epilepsy can vary markedly across income levels. In a 2014 report in Epilepsy Research, Dr. Hauser and colleagues from The Prevalence of Epilepsy in Rural Kansas Study group used a specialized statistical method (capture-recapture) to estimate a substantially higher prevalence of the condition in two rural, predominantly Caucasian counties in Kansas.

Dr. Zack emphasized the importance of the new 2017 Classification of Seizures by the International League Against Epilepsy, which replaces the traditional classification with more specific criteria based on location in the brain and other specific features of the seizure. He said the new criteria are liable to capture more patients than may have been captured in the CDC study relying on patient self-reports.

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LINK UP FOR MORE INFORMATION:

•. Zack MM, Kobau R. National and state estimates of the numbers of adults and children with active epilepsy — United States, 2015 https://http://www.cdc.gov/mmwr/volumes/66/wr/mm6631a1.htm. MMWR Morb Mortal Wkly Rep 2017;66: 821–825.
© 2017 American Academy of Neurology