Idiopathic Intracranial Hypertension More Likely With High BMI, Socioeconomic Deprivation

Latif Miah, MBBCH

Data from a recent study suggest that idiopathic intracranial hypertension (IIH) is increasing in prevalence in correspondence to population increases in body mass index (BMI) and socioeconomic deprivation.

Obese individuals were found to have an odds ratio (OR) of 1.14 (95% CI, 1.13-1.14; P <.00001) of developing IIH compared to non-obese people. The least deprived quintile was 0.65 times (95% CI, 0.55-0.76) as likely to develop IIH than the most deprived quintile after adjusting for gender and BMI. 

First author Latif Miah, MBBCH, foundation doctor, Swansea Bay University Health Board, and colleagues wrote that “IIH incidence and prevalence in Wales are increasing considerably, corresponding to population increases in BMI. IIH is associated with increasing deprivation in women even after adjusting for obesity suggesting additional etiological factors associated with deprivation apart from BMI. This effect was not seen in men pointing to sex-specific drivers for IIH.”

Miah and colleagues analyzed 35 million patient years' worth of data. In 2017, there were 1765 cases of IIH, 85% (n = 1500) of which were women. In 2015, 35.9% of people in the most deprived quintile were obese compared to 24.4% in the least deprived quintile.

They found that the prevalence of IIH was 76 out of 100,000 and incidence was 7.8 out of 100,000 per year in 2017. These are significant increases from 2003, which had an IIH prevalence of 12 out of 100,000 and an incidence of 2.3 out of 100,000 (P <.001).

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Obese women had a mean IIH prevalence of 180 per 100,000 and an incidence of 23.5 per 100,000 per year, while women with an ideal BMI had an IIH prevalence of 13.2 per 100,000 and 1.6 per 100,000 per year. Obese men had a mean IIH prevalence of 21.2 per 100,000 and an incidence of 2.6 per 100,000 per year, while men with an ideal BMI had an IIH prevalence of 7.6 per 100,000 and an incidence of 1.6 per 100,000 per year.

Obese men had an OR of 1.10 (1.08-1.12; P <.00001) of developing IIH compared to non-obese men, while obese women had an OR of 1.13 (1.13-1.14; P <.00001) compared to non-obese women. After adjusting for BMI, women in the most deprived quintile were around 1.5 times more likely to develop IIH than those in the least deprived quintile (least deprived OR, 0.65; [95% CI, 0.54-0.77]; P <.00001). In men, IIH was only associated with BMI and not deprivation. Altogether, women were found to be 4 times more likely to develop IIH than men (OR, 3.96; [95% CI, 3.51-4.50; P <.00001).

Miah and colleagues also followed outcomes of patients and found that 13 (0.78%) patients were recorded as being blind at a mean of 858 days after IIH diagnosis while 32 (1.9%) patients were recorded as having at least moderate visual impairment at a mean of 804 days after IIH diagnosis. Cerebrospinal fluid (CSF) diversion procedures were performed on 158 (9%) patients at a mean of 491 days after diagnosis. Of these patients, 70 (44%) went on to have at least 1 revision surgery. At a mean of 5.1 years after diagnosis, BMI increased by 0.48 kgm-2 (95% CI, 0.07-0.89; P = .02) in the 691 patients that BMI follow-up data was available.

Patients in the IIH cohort had 4818 unscheduled hospital visits over 3,262,942 days during the study period, for a mean rate of 0.54 visits per patient per year. The control cohort had 2755 over 9,860,456 days for a mean rate of 0.10 visits per patient per year. The ratio of IIH cohort visits compared to control was 5.28 (95% CI, 5.04-5.54), which corresponds to the 777 unscheduled visits in the IIH cohort compared to control.

Patients with IIH that underwent CSF diversion surgery had 1215 unscheduled hospital visits over 407,751 days for a mean rate of 1.088 visits per patient per year. The rate ratio of visits for these patients compared to IIH patients without CSF shunts was 2.02 (95% CI, 1.89-2.15; P <.01).

“The increasing incidence of IIH, together with the increased healthcare utilization in in individuals with IIH and particularly those who have had CSF shunts have important implications for healthcare professionals and policy makers,” Miah and colleagues concluded.

REFERENCE

Miah L, Strafford H, Fonferko-Shadrach B, et al. Incidence, prevalence and healthcare outcomes in idiopathic intracranial hypertension: A population study. Neurology. Published online January 20, 2021. doi: 10.1212/WNL.0000000000011463