Re-evaluating the Incidence of Idiopathic Intracranial Hypertension in an Era of Increasing Obesity.

Purpose: To re-evaluate the population-based incidence of idiopathic intracranial hypertension (IIH) and to determine if it mirrors the rise in obesity.

Design: Retrospective, population-based cohort.

Participants: All residents of Olmsted County, Minnesota, diagnosed with IIH between January 1, 1990, and December 31, 2014.

Methods: All cases of IIH were identified using the Rochester Epidemiology Project, which is a record-linkage system of medical records for all patient-physician encounters among Olmsted County, Minnesota, residents. All medical records were reviewed to confirm a diagnosis of IIH. The incidence rates of IIH were compared against the incidence of obesity in Minnesota over the same period.

Main Outcome Measures: Incidence of IIH, lumbar puncture opening pressures, and body mass index.

Results: There were 63 new cases of IIH, yielding an overall age- and gender-adjusted annual incidence of 1.8 per 100 000 (95% confidence interval, 1.3-2.2) between 1990 and 2014. It increased from 1.0 per 100 000 (1990-2001) to 2.4 per 100 000 (2002-2014; P = 0.007). The incidence of IIH was 3.3 per 100 000 in women and 0.3 per 100 000 in men (P ≤ 0.001). In obese women 15 to 44 years of age, the incidence was 22.0 per 100 000 compared with 6.8 per 100 000 among all women in the same age group. A strong correlation was observed between IIH incidence rates and obesity rates in Minnesota (R = 0.70, P = 0.008).

Conclusions: The incidence of IIH has increased since 1990, which is highly correlated with the rise in obesity during the same period.