Social Determinants of Health in Idiopathic Intracranial Hypertension

Idiopathic intracranial hypertension (IIH) is a disorder of elevated intracranial pressure that occurs primarily in premenopausal women. Obesity is the primary risk factor for IIH¹, and obesity has been linked to a number of adverse social determinants of health. Specifically, individuals who are overweight or obese are more likely to come from traditionally marginalized racial and ethnic groups, have lower annual income, and live in neighborhoods with limited access to healthy food or outdoor space^2,3. Using data from a single metropolitan academic center, we have previously shown that women with IIH are more likely to be Black or Hispanic and live in neighborhoods with a preponderance of unhealthy food establishments (also known as “food swamps”)⁴. However, social determinants of health in IIH have not been examined on a nationwide scale. In this study, we examined social determinants of health in a nationwide IIH cohort within the National Institutes of Health (NIH) All of Us program.

Methods:

Study Population:

We analyzed cross-sectional data from the NIH All of Us Research program. This program aims to enroll a diverse sample of one million United States (U.S.) residents, collecting a wide range of physical measurements, patient-reported outcomes, electronic health records (EHR), and biospecimens. Participants are recruited through a large nationwide network of community-based healthcare providers, clinical laboratories, pharmacies, and other community organizations. We used version 6 of the controlled tier dataset, which included subjects enrolled between May 1, 2018 and January 1, 2022. The study was approved by the NIH All of Us institutional review board (IRB), and participants provided informed consent prior to enrollment. Secondary analysis of de-identified data was exempted from approval by the University of Pennsylvania IRB.

Using EHR diagnosis codes, we identified All of Us participants with IIH, excluding those with alternative diagnoses such as dural sinus thrombosis, meningitis, hydrocephalus, or central nervous system neoplasm (Supplemental Table 1). Because the vast majority of people with IIH are women, and there is a high prevalence of non-IIH causes of papilledema in men⁵, we restricted both IIH cases and persons without IIH to participants who reported being assigned “female” at birth. We also restricted the sample to individuals aged 18 to 50 to reflect the known epidemiology of IIH.

Statistical Analysis:

Our primary outcomes were social determinants of health related to healthcare access and quality of life, which were self-reported. These included employment status, experiences with delaying healthcare due to financial constraints, lack of transportation, and geographical barriers in accessing care. Covariates included age at enrollment, annual income (categorized as less than $25,000, $25,000 to $50,000, $50,000 to $100,000, or over $100,000) and self-reported race/ethnicity (categorized as non-Hispanic Black, non-Hispanic White, Hispanic, and other). Body mass index (BMI) was calculated using baseline height and weight. We summarized the characteristics of women with and without IIH and used logistic regression to compare the prevalence of each social determinant of health, adjusting for age, race, ethnicity, annual income, and BMI. Statistical analyses were performed on the NIH All of Us Researcher Workbench using R software version 4.1.0, and statistical significance was defined at the p<0.05 level.

Results:

Of 369,483 participants in the NIH All of Us program at the time of analysis, we identified 416 women with IIH and 107,111 women without IIH (Figure 1). The mean age of the cohort was 38 years, and 49.3% identified as non-White. The demographic characteristics of women with and without IIH are summarized in Table 1. Median BMI was higher in women with IIH (38.19 kg/m²) than those without IIH (28.80 kg/m²), consistent with the known epidemiology of IIH. Women with IIH were more likely to identify as non-Hispanic Black or African American (30.3%) than those without IIH (20.4%; OR 1.67, 95% CI: 1.32–2.10). This remained statistically significant after adjusting for age (OR 1.66, 95% CI: 1.32–2.09), but after additionally adjusting for BMI and annual income, the association between race and IIH attenuated and was no longer statistically significant (OR 1.27, 95% CI: 0.96–1.68). There was no difference in the proportion of women with and without IIH who identified as Hispanic or Latino in either unadjusted (OR 0.97, 95% CI: 0.76–1.24) or adjusted (AOR 0.81, 95% CI: 0.60–1.10) analyses.

Figure 1: Study inclusion and exclusion criteria.

Table 1:

Demographic characteristics of women with idiopathic intracranial hypertension and controls in the NIH All of Us program

	IIH (n=416)	No IIH (n=107,111)
Age, mean (years)	39.06 (SD 7.98)	38.15 (SD 9.17)
BMI, median (kg/m2)	38.19 (IQR: 11.57–65.93)	28.80 (IQR: 6.85–52.37)
Race/ethnicity
Non-Hispanic White	180 (45.0%)	49,225 (50.8%)
Non-Hispanic Black	121 (30.3%)	19,826 (20.4%)
Hispanic	99 (24.8%)	27,920 (28.8%)
Education
College or advanced degree	138 (33.7%)	45,754 (43.4%)
1 to 3 years (some college)	156 (38.0%)	29,242 (27.7%)
High School Graduate	86 (21.0%)	20,872 (19.8%)
Less than high school	30 (7.3%)	9,556 (9.1%)
Unemployed	197 (47.4%)	38,588 (36.0%)
Annual income
<25,000	134 (40.9%)	29,984 (34.2%)
25,000–50,000	75 (22.8%)	18,927 (21.6%)
50,000–100,000	75 (22.8%)	19,324 (22.0%)
>100,000	44 (13.4%)	19,431 (22.2%)

SD, standard deviation; IQR, interquartile range

Among those who completed the healthcare access and quality of life questionnaires, women with IIH were more likely to be unemployed (OR: 1.60, 95% CI: 1.32–1.95) and have lower income (OR: 1.97, 95% CI: 1.40–2.78) compared to women without IIH in unadjusted logistic regression models. Women with IIH were also more likely to delay care due to rural residence (OR: 2.34, 95% CI: 1.43–3.81), difficulties accessing transportation (OR: 2.58, 95% CI: 1.83–3.64), and inability to afford copay (OR: 1.62, 95% CI: 1.14–2.30) or the cost of seeing a specialist (OR: 1.59, 95% CI: 1.12–2.27). These remained statistically significant after adjustment (Table 2).

Table 2:

Association between idiopathic intracranial hypertension and social determinants of health

	IIH (n=416)	No IIH (n=107,111)	Unadjusted OR (95% CI)	Adjusted OR1 (95% CI)
Unemployed	197 (47.4%)	38,588 (36.0%)	1.60 (1.32–1.95)	1.40 (1.14–1.71)
Delay care: Rural residence	N/A	N/A	2.34 (1.43–3.81)	2.08 (1.25–3.47)
Delay care: Transportation difficulty	43/180(23.9%)	4,689/43,213 (11.1%)	2.58 (1.83–3.64)	2.23 (1.55–3.20)
Delay care: Can’t afford copay	41/177(23.2%)	6,530/41,603 (15.7%)	1.62 (1.14–2.30)	1.47 (1.02–2.10)
Delay care: Can’t afford out-of-pocket costs	56/175 (32.0%)	10,685/41,419 (25.8%)	1.35 (0.98–1.86)	1.51 (1.09–2.09)
Delay care: Can’t afford specialist	40/177 (22.6%)	6,486/41,840 (15.5%)	1.59 (1.12–2.27)	1.52 (1.06–2.18)
One or more reason for delaying care	83/158(52.5%)	11,111/29,286 (37.9%)	1.81 (1.32–2.48)	1.64 (1.19–2.25)

¹Adjusted for age, race/ethnicity, and BMI

Counts and frequencies for delayed care due to rural residence are not shown due to NIH All of Us cell suppression requirements. IIH, idiopathic intracranial hypertension; OR, odds ratio; CI, confidence interval.

Conclusions:

In this study, we aimed to investigate the impact of social determinants of health in patients with IIH in the U.S. We found that women with IIH were more likely to report lower income and employment and greater barriers to healthcare access compared to those without IIH. Women with IIH were also more likely to be Black or Hispanic, but this association attenuated after adjusting for confounders such as BMI and annual household income. These findings highlight the importance of social determinants of health in IIH.

First, we found that women with IIH were more likely to report multiple indicators of low socioeconomic status, including lower annual income and employment rates, than women without IIH. Some of this relationship may reflect the known associations between socioeconomic status and obesity, the primary risk factor for IIH. However, these associations remained significant even after adjusting for BMI and other confounders, which suggests that social determinants of health may contribute to IIH through other mechanisms besides obesity alone. Women with IIH were also more likely to report being unable to afford copays, out-of-pocket costs, and specialist visits. Because IIH requires prompt diagnosis and treatment in order to prevent irreversible vision loss, delays in accessing care have significant consequences for this population. Delays in care are not unique to IIH and are known to occur in other vulnerable disease populations. In the All of Us research program, for example, the proportion of patients with diabetic retinopathy who delayed care due to transportation limitations is similar to what we observed in IIH⁶. Transportation limitations are also more frequently reported in individuals with chronic neurologic diseases such as epilepsy⁷. Of note, employment status encompasses both voluntary participation or non-participation in the workforce and unemployment due to unintended loss of employment. In this context, the prevalence of unemployment in our non-IIH population was similar to nationwide estimates from the American Community Survey⁸.

In our unadjusted analyses, women with IIH were more likely to report Black ancestry compared to those without IIH, consistent with large academic center and nationwide hospitalization data^4,9,10. However, after adjusting for BMI and annual household income, Black women were no more likely to be diagnosed with IIH than White women. This suggests that racial and ethnic disparities in the prevalence of IIH are driven by socioeconomic risk factors for obesity rather than any actual biological differences. A number of social determinants of health have been tied to racial disparities in obesity prevalence, including geographic proximity to unhealthy food establishments and a lack of access to health foods^2,3.

An unexpected finding was that women with IIH were more likely to report delays in care associated with living in a rural area. This suggests that a larger proportion of the IIH population lives in rural communities than previously thought. Because most neuro-ophthalmologists are located within large metropolitan areas¹¹, limited access to specialized resources in rural communities may impede the timely diagnosis, treatment, and management of IIH.

Several limitations should be considered when interpreting the results of our study. First, social determinants of health were self-reported and completed by a subset of participants, which may be subject to recall and selection bias, respectively. Second, the potential for misdiagnosis in the electronic health record should be acknowledged, as IIH is a diagnosis of exclusion, and previous studies have suggested that it is overdiagnosed in clinical practice¹². Previous studies have shown that the positive predictive value of a single ICD-9 code for IIH increases from 55–65% to 90% when medication information is included but this as well as other data such as MRI and lumbar puncture were not available in this study¹³. Finally, the lack of longitudinal information about IIH severity and outcomes limits our understanding of the long-term impact of social determinants of health. Future research should examine the effect social determinants of health on visual outcomes, healthcare utilization, and weight loss in IIH.