Prevalence of narcolepsy in King County, Washington, USA

Longstreth, W.T.; Ton, Thanh G.N.; Koepsell, Thomas; Gersuk, Vivian H.; Hendrickson, Audrey; Velde, Sarah

doi:10.1016/j.sleep.2008.05.009

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Volume 10, Issue 4 , Pages 422-426, April 2009

Prevalence of narcolepsy in King County, Washington, USA☆

W.T. Longstreth Jr.
- Neuroepidemiology Group, University of Washington, Seattle, WA, USA
- Department of Neurology, School of Medicine, University of Washington, Seattle, WA, USA
- Department of Epidemiology, School of Public Health and Community Medicine, University of Washington, Seattle, WA, USA
- Corresponding author. Address: Department of Neurology, Box 359775, Harborview Medical Center, 325 Ninth Avenue, Seattle, WA 98040-2420, USA. Tel.: +1 206 744 3251; fax: +1 206 744 8787.
Thanh G.N. Ton
- Neuroepidemiology Group, University of Washington, Seattle, WA, USA
- Department of Neurology, School of Medicine, University of Washington, Seattle, WA, USA
- Department of Epidemiology, School of Public Health and Community Medicine, University of Washington, Seattle, WA, USA
Thomas Koepsell
- Neuroepidemiology Group, University of Washington, Seattle, WA, USA
- Department of Epidemiology, School of Public Health and Community Medicine, University of Washington, Seattle, WA, USA
- Department of Health Services, School of Public Health and Community Medicine, University of Washington, Seattle, WA, USA
- Department of Medicine, School of Medicine, University of Washington, Seattle, WA, USA
Vivian H. Gersuk
- The Benaroya Research Institute at Virginia Mason, Seattle, WA, USA
Audrey Hendrickson
- Neuroepidemiology Group, University of Washington, Seattle, WA, USA
- Department of Neurology, School of Medicine, University of Washington, Seattle, WA, USA
Sarah Velde
- Neuroepidemiology Group, University of Washington, Seattle, WA, USA
- Department of Neurology, School of Medicine, University of Washington, Seattle, WA, USA

Received 19 September 2007; received in revised form 24 May 2008; accepted 28 May 2008.

Abstract

Background

Relatively few epidemiologic studies have focused on narcolepsy, a disabling sleep disorder with a strong association with HLA-DQB1∗0602.

Methods

We sought to estimate the prevalence of narcolepsy using multiple overlapping techniques to identify residents of King County, WA who were 18 years or older with physician-diagnosed narcolepsy. Patients were entered into a registry and recruited into an epidemiologic study entailing interview and buccal scrapings to determine HLA-DQB1∗0602 status. Missing values were imputed to allow prevalence to be estimated based on all 425 patients entered into the registry between 2001 and 2005, whether they were recruited into the epidemiologic study (n=279) or not (n=146).

Results

As of July 01, 2001, estimated prevalence per 100,000 of physician-diagnosed narcolepsy with cataplexy was 21.8 (95% confidence interval (CI): 18.8–24.8), similar to prior studies. The median age of onset was 14 (interquartile range: 10–18). For narcolepsy with HLA-DQB1∗0602, prevalence was 15.3 (95% CI: 12.8–17.9). Estimated prevalence was higher in women than men and in African-Americans than other racial groups.

Conclusions

These differences could reflect problems in identification and recruitment or may provide etiologic clues about narcolepsy. This study illustrates the challenges in performing population-based studies of narcolepsy.

Keywords: Narcolepsy, Cataplexy, HLA-DQB1∗0602, Epidemiologic studies, Prevalence, Incidence