• New population-based data from a single county in Minnesota have revealed an increased incidence of idiopathic intracranial hypertension (IIH) in the last 2 decades, and is highly correlated with the rise in obesity during the same period.

    Much of the knowledge on the incidence of IIH came from a prior study conducted from 1976 through 1990 by the Rochester Epidemiology Project, which established an incidence of 1.0 per 100,000 persons.

    In this latest study, investigators reevaluated the same population in Minnesota and identified 63 new cases of IIH between 1990 and 2014. They found that that the overall age- and gender-adjusted annual incidence of IIH had increased to 1.8 per 100,000. When they compared the incidence rates of IIH against the incidence of obesity in Minnesota over the same period, they found a strong and significant correlation between the 2 conditions (P=0.008).

    Additionally, there was a significant rise in the incidence of IIH from the first half of the study at 1.0 per 100,000 persons (1990–2001) to 2.4 per 100,000 persons in the second half of the study (2002–2014; P=0.007).

    Consistent with previous findings, the incidence of IIH was significantly higher among women: 3.3 per 100 000 compared with just 0.3 per 100 000 in men. Additionally, incidence rates were 3-fold higher among obese women compared with all included females.

    Some of the limitations of this study include the retrospective design and the racial homogeneity of the study population. Approximately 90% of the study population identified themselves as white, and thus it may be difficult to extrapolate these results to nonwhite populations.

    Key take-home points

    • The estimated overall annual incidence of IIH has increased to 1.8 per 100,000, almost double the 1.0 per 100,000 rate reported between 1976 and 1990.
    • The increased incidence of IIH was strongly correlated with the rise in obesity during the same period.
    • Incidence of IIH was 11-fold higher among women than men, and 3-fold higher among obese women compared with all females.