Current Trends Prevalence of Self-Reported Epilepsy -- United States, 1986-1990

Epilepsy is a chronic neurologic condition characterized by abnormal electrical discharges in the brain manifested as two or more unprovoked seizures (1). Risk factors for epilepsy include vascular disease, head trauma, congenital or perinatal factors, central nervous system infections, and neoplasms; however, the etiology of epilepsy is unknown for approximately three fourths of cases (2). Epilepsy frequently causes impaired physical, psychological, and social functioning, which results in substantial disability, economic loss, and diminished quality of life (3). To examine the burden of epilepsy in the United States, the prevalence of self-reported epilepsy was estimated by using data from 1986 through 1990 from the National Health Interview Survey (NHIS) (4). This report summarizes the results of this analysis.

The NHIS is a nationally representative household survey of the U.S. civilian, noninstitutionalized population conducted annually by CDC. Respondents were asked whether they or any household family member had epilepsy or repeated seizures, convulsions, or blackouts during the preceding 12 months. Self-reported epilepsy was categorized according to the International Classification of Diseases, Ninth Revision, Clinical Modification, codes 345.0-345.9. Age-specific and age-adjusted prevalences for the 12-month period preceding the interview and associated standard errors were estimated; the direct method was used to age-adjust the estimates, using the 1980 U.S. resident population as the standard (5). To increase the stability of the estimates, data were combined for 1986-1990. Confidence intervals (CIs) were based on the standard errors of the estimates, taking into account the survey design.

During 1986-1990, approximately 1.1 million persons in the United States annually reported having epilepsy. The overall prevalence of epilepsy was 4.7 cases per 1000 persons. The prevalence was lowest (3.1) for persons aged greater than or equal to 65 years and highest (5.2) for persons aged 15-64 years Table_1. The prevalence for persons aged less than 15 years was 4.0. The age-adjusted prevalence was similar for women and men (5.1 and 4.2, respectively), and the age-specific pattern was consistent for both sexes. The age- and race-adjusted prevalence of epilepsy was similar among the regions of the country (4.0 in the West, 4.4 in the Northeast, 4.9 in the Midwest, and 5.0 in the South) * .

The age-adjusted prevalence of epilepsy was higher for blacks (6.7 {95% CI=4.9-8.5}) than whites (4.5 {95% CI=3.9-5.1}). ** Compared with whites, prevalence rates among blacks were especially higher for persons aged 35-44 years and 45-54 years (prevalence ratios=3.0 and 2.3, respectively) (Figure_1, page 817). This pattern was similar for both black males and black females. Reported by: Statistics Br, Div of Chronic Disease Control and Community Intervention, National Center for Chronic Disease Prevention and Health Promotion; National Center for Health Statistics, CDC.

Editorial Note

Editorial Note: The findings in this report indicate that epilepsy is a common neurologic condition in the United States. However, the overall age-adjusted prevalence in this report (4.7) is lower than estimates from previous studies (6.0-7.0), which were based on rigorous case ascertainment efforts (i.e., record review or neurologic examination) in more clearly defined local populations (2,6).

Epileptic seizures can be classified by etiology or clinical manifestation. Seizures with a presumptive cause (e.g., head trauma, stroke, or neoplasm) are classified as symptomatic seizures or secondary epilepsy; repeated seizures with no presumed cause are classified as idiopathic epilepsy (7). Symptomatic seizures can be either acute or temporally remote from the triggering event and can be prevented by reducing the prevalence of the predisposing event. However, even if all known risk factors for epilepsy were removed from the population, approximately 70% of cases would still occur (2).

The findings in this report are subject to at least two limitations. First, estimates are based on self-reported data and may be subject to reporting bias. For example, because a social stigma is associated with epilepsy, persons may be reluctant to report the condition (8). Second, epilepsy manifests itself with varying seizure frequency throughout life. Persons whose seizures are controlled with medication or who have not had a recent seizure may not have reported epilepsy as a medical problem in this survey.

The higher reported prevalence of epilepsy for blacks than for whites is consistent with previous reports (6,9). Among blacks, the higher prevalences in middle-aged groups (i.e., 35-44 years and 45- 54 years) may reflect differences in the epidemiology of epilepsy in middle life (e.g., trauma and cerebrovascular disease). Because most previous studies have reported a higher prevalence of epilepsy among males, the detection of similar prevalences for men and women in this report warrants further assessment (9).

Prompt detection and early medical intervention can greatly improve seizure control and enhance the quality of life for persons with epilepsy; however, epilepsy remains undiagnosed or inadequately treated in many persons. To address these issues, CDC is collaborating with professional and voluntary organizations to design provider and consumer education materials to improve awareness, detection, and appropriate treatment of persons with epilepsy.

November is National Epilepsy Month. For additional information about epilepsy management or referral to local resources, contact the Epilepsy Foundation of America, telephone (800) 332-1000 or (301) 459-3700.

References

1. Adams RD, Victor M. Principles of neurology. 4th ed. New York: McGraw-Hill, 1989.

2. Hauser WA, Kurland LT. The epidemiology of epilepsy in Rochester, Minnesota, 1935 through 1967. Epilepsia 1975;16:1-66.

3. Hartshorn JC, Byers VL. Impact of epilepsy on quality of life. J Neurosci Nurs 1992;24:24-9.

4. NCHS. Current estimates from the National Health Interview Survey: data from the national health survey, 1989. Hyattsville, Maryland: US Department of Health and Human Services, Public Health Service, CDC, 1990; DHHS publication no. (PHS)90-1504. (Vital and health statistics; series 10, no. 176).

5. Fleiss JL. Statistical methods for rates and proportions. 2nd ed. New York: John Wiley & Sons, 1981.

6. Haerer AF, Anderson DW, Schoenberg BS. Prevalence and clinical features of epilepsy in a biracial United States population. Epilepsia 1986;27:66-75.

7. Commission on Classification and Terminology, International League Against Epilepsy. Proposal for revised clinical and electroencephalographic classification of epileptic seizures. Epilepsia 1981;22:489-501.

8. Jacoby A. Felt versus enacted stigma: a concept revisited -- evidence from a study of people with epilepsy in remission. Soc Sci Med 1994;38:269-74.

9. Hauser WA, Hesdorffer DC. Epilepsy: frequency, causes and consequences. New York: Epilepsy Foundation of America, 1990.

* Northeast=Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, and Vermont; Midwest=Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, and Wisconsin; South=Alabama, Arkansas, Delaware, District of Columbia, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia, and West Virginia; West=Alaska, Arizona, California, Colorado, Hawaii, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming. 

** Numbers for races other than black and white were too small for meaningful analysis.

TABLE 1. Frequency and prevalence of self-reported epilepsy, by sex and age group
-- United States, 1986-1990
===================================================================================
                                         Age group (yrs)
                          ----------------------------------------
Sex                        0-14         15-64           >65            Total
-----------------------------------------------------------------------------------
Male
  No. *                    492           1854           132             2478
  Prevalence +             3.6            4.8           2.2              4.2
  (95% CI &)            (2.2-5.0)      (3.8-6.8)     (0.6-3.8)        (3.4-5.0)

Female
  No.                      566           2280           306             3152
  Prevalence               4.4            5.6           3.7              5.1
  (95% CI)              (3.0-5.8)      (4.6-6.6)     (1.9-5.5)        (4.3-5.9)

Total @
  No.                     1058           4134           438             5630
  Prevalence               4.0            5.2           3.1              4.7
  (95% CI)              (3.0-5.0)      (4.4-6.0)     (1.9-4.3)        (4.1-5.3)
-----------------------------------------------------------------------------------
* In thousands.
+ Per 1000 civilian, noninstitutionalized persons in the United States.
& Confidence interval.
@ Age-adjusted to the 1980 U.S. population.
===================================================================================

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