Nationwide prevalence and geographic variation of idiopathic intracranial hypertension among women in the United States

Muhammad A Fraz; B Michelle Kim; John J Chen; Flora Lum; Jinbo Chen; Grant T Liu; Ali G Hamedani; SOURCE Consortium

doi:10.1016/j.ophtha.2024.10.031

Nationwide prevalence and geographic variation of idiopathic intracranial hypertension among women in the United States

Ophthalmology. 2024 Nov 5:S0161-6420(24)00686-9. doi: 10.1016/j.ophtha.2024.10.031. Online ahead of print.

Authors

Muhammad A Fraz¹, B Michelle Kim², John J Chen³, Flora Lum⁴, Jinbo Chen⁵, Grant T Liu⁶, Ali G Hamedani⁷; SOURCE Consortium

Affiliations

¹ Departments of Neurology and Ophthalmology, Perelman School of Medicine, University of Pennsylvania.
² Mayo Clinic School of Medicine, Rochester, MN.
³ Departments of Neurology and Ophthalmology, Mayo Clinic, Rochester, MN.
⁴ American Academy of Ophthalmology, San Francisco, CA.
⁵ Department of Biostatistics, Epidemiology, and Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.
⁶ Departments of Neurology and Ophthalmology, Perelman School of Medicine, University of Pennsylvania; Division of Ophthalmology, Children's Hospital of Philadelphia, Philadelphia, PA.
⁷ Departments of Neurology and Ophthalmology, Perelman School of Medicine, University of Pennsylvania; Department of Biostatistics, Epidemiology, and Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA. Electronic address: [email protected].

PMID: 39510331
DOI: 10.1016/j.ophtha.2024.10.031

Abstract

Objective: The prevalence of idiopathic intracranial hypertension (IIH) is increasing, but this has not been examined on a nationwide scale. Our objective was to determine the nationwide prevalence and geographic distribution of IIH among women in the U.S.

Design: Retrospective cross-sectional study using Medicaid claims and electronic health record data from the IRIS® Registry (Intelligent Research in Sight) and Sight Outcomes Research Collaborative (SOURCE).

Participants: Female Medicaid beneficiaries aged 18-55 with IIH diagnoses and prescriptions for acetazolamide or methazolamide in 2018, excluding those with other causes of intracranial hypertension. We also calculated the proportion of female IIH patients in the U.S. who were insured by Medicaid by combining analyses from the IRIS® Registry and SOURCE.

Methods: To calculate the total number of IIH patients in the U.S. and by state, we divided the number of Medicaid beneficiaries with IIH by the proportion of IIH patients insured by Medicaid. We then used census data from the 2018 American Community Survey to calculate prevalence.

Main outcome measures: We compared the geographic distribution of IIH to obesity prevalence data from the 2018 Behavioral Risk Factor Surveillance System, using the Moran's I statistic to test for spatial variation. In a validation study, we compared the calculated prevalence of IIH in Minnesota to similar data from the Rochester Epidemiology Project.

Results: Of 13,959 female Medicaid beneficiaries with IIH, 6,828 had a prescription for acetazolamide or methazolamide. In the IRIS® Registry and SOURCE, 25% of IIH patients were insured by Medicaid (95 % CI: 16-33%), suggesting that there were 27,312 women aged 18-55 with IIH taking acetazolamide or methazolamide in 2018 (6,828 / 0.25 = 27,312). Prevalence was 3.44 per 10,000 (95% CI: 2.61-5.39), and there was significant geographic variation (Moran's I statistic 0.20, P = 0.03) with higher prevalence in states where obesity was more common. The calculated prevalence of IIH in Minnesota was statistically equivalent to Rochester Epidemiology Project data (P < 0.05 for equivalence test).

Conclusions: IIH affects 3.44 per 10,000 women aged 18-55 in the U.S., and there is significant geographic variation, some of which is explained by variation in obesity prevalence.