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Show Original Contribution Section Editors: Clare Fraser, MD Susan Mollan, MD Idiopathic Intracranial Hypertension and Socioeconomic Status in the Greater Toronto Area, Canada Arshia Eshtiaghi, BHSc, MD(C), Edward A. Margolin, MD, Jonathan A. Micieli, MD Background: Previous studies have identified an association between obesity and socioeconomic variables such as poverty, minority status, and a low level of education. Because obesity is a major risk factor for the development of idiopathic intracranial hypertension (IIH), this study aims to identify and assess relationships between socioeconomic and geographic variables in patients with IIH in Canada. Methods: A retrospective chart review was performed to identify female patients with IIH presenting to 2 neuroophthalmology clinics in Toronto between 2014 and 2022. Consecutive female patients younger than 50 years who did not have IIH were identified as controls. Patient age, body mass index (BMI), and postal code were obtained from electronic medical records. Patient postal codes were then converted to geographic dissemination areas based on the 2016 Canadian census, and data on socioeconomic outcomes were collected from Statistics Canada. Results: Three hundred twenty-two female patients with IIH (mean age: 32.3 ± 10) and 400 female controls (mean age: 33.9 ± 9) were included. The mean BMI was 35.0 ± 8 for patients with IIH and 26.7 ± 7 for control patients (P , 0.00001). There was a significant difference between dissemination areas resided by patients with IIH and control patients for median income ($34640 vs $36685 CAD, P = 0.02) and rate of postsecondary degree attainment (57.7% vs 60.5%, P = 0.01). There were no significant differences in the percentage of visible minorities, percentage of immigrants, knowledge of official languages, percentage of married individuals, average household size, or unemployment rate. There was a weak but significant inverse relationship between the rate of postsecondary degree attainment in dissemination areas resided by patients with IIH and their BMI (P = 0.01, R2 = 0.02). Conclusion: Patients with IIH reside in geographic areas with lower average levels of income and education than control patients. Patients with lower levels of education may Faculty of Medicine (AE), Department of Ophthalmology and Vision Sciences (EM, JAM), Division of Neurology (EM, JAM), Department of Medicine, University of Toronto, Toronto, Canada; and Kensington Vision and Research Centre (JAM), Toronto, Canada. The authors report no conflicts of interest. Address correspondence to Jonathan A. Micieli, MD, Kensington Vision and Research Centre, 340 College Street, Suite 501, Toronto, ON, Canada, M5T 3A9; E-mail: jonathanmicieli@gmail.com Eshtiaghi et al: J Neuro-Ophthalmol 2023; 43: 197-201 be at higher risk of elevated BMI and therefore disease incidence and progression. Journal of Neuro-Ophthalmology 2023;43:197–201 doi: 10.1097/WNO.0000000000001680 © 2022 by North American Neuro-Ophthalmology Society I diopathic intracranial hypertension (IIH) is a disease of increased intracranial pressure with normal cerebrospinal fluid composition in the absence of a detectable intracranial cause (1). As a result of this condition, patients may experience systemic symptoms such as headache and are at risk for irreversible vision loss due to papilledema (2). IIH has an unknown etiology; however, it occurs predominantly in young women with elevated body mass index (BMI) (2). Despite inconclusive evidence, the risk of obesity tends to increase among those with lower levels of income and education (3,4) and among those of certain racial backgrounds (5). By extrapolation, IIH would be expected to display disparities in these same socioeconomic and demographic factors. In a recent cohort of patients presenting to a neuroophthalmology clinic in Philadelphia, IIH was found to be more common in Black and Hispanic women who were obese, with suggested associations being partly driven by low income and proximity to unhealthy foods (6). Given the globally increasing prevalence of obesity (7), the incidence of IIH is also on the rise. Disease morbidity and mortality have long been linked to socioeconomic status, yet no studies have examined such an association with IIH in Canada. Thus, studying how socioeconomic and demographic factors relate to the incidence of IIH may help us better understand its modifiable risk factors and could aid legislation and social policies in addressing the needs of the community. Such data would facilitate patient risk stratification to improve patient triage, clinical decision making, and to identify patients who would benefit from more frequent monitoring and more aggressive treatment strategies. Therefore, the primary objective of this study was to explore differences in the socioeconomic background of 197 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Original Contribution patients with IIH and controls by analyzing aggregate census data. The secondary objective of this study was to determine whether there is any relationship between BMI and socioeconomic variables among patients with IIH. METHODS Patient Identification A retrospective chart review was performed to identify female patients presenting to 2 neuro-ophthalmology clinics in Toronto between February 2014 and February 2022 who were subsequently diagnosed with IIH. The diagnosis of IIH was made by 2 fellowship-trained neuroophthalmologists (J.A.M and E.M) based on the modified Dandy criteria. Another chart review was performed to identify consecutive patients referred to the neuroophthalmology clinics who were not diagnosed with IIH to act as controls. Given that IIH is a disease that predominantly occurs in young women, control patients were restricted to women younger than 50 years. Patients with missing addresses on their electronic medical records were excluded. Prospective institutional ethics board approval from the University of Toronto was obtained before initiation of this study. Data Collection Standardized data collection forms were used to obtain the following data from patients’ electronic medical records: age, sex, postal code, and BMI (when available). Census data from 2016 (the most recently available data at the time of this study) were obtained from the Statistics Canada website, the official government source for verified census information (8). Patient postal codes were converted to dissemination areas, which are the smallest geographic units of analysis provided by Statistics Canada. For each patient’s dissemination area, the following data were obtained: median total income among recipients, rate of postsecondary degree attainment, percentage of visible minorities, percentage of immigrants, knowledge of official languages, percentage of married individuals, average household size, and unemployment rate. Data Analysis Descriptive statistics were reported as means and standard deviations for continuous outcomes (e.g., age and BMI). The primary outcome was the difference in means of socioeconomic variables between patients with IIH and control patients. A 2-tailed t test assuming unequal variance was performed to compare the means of outcomes in the IIH and control groups. The secondary outcome was the association of BMI with socioeconomic variables. Linear regression analysis was subsequently performed to deter198 mine the relationship between BMI and any significant outcome from the previous analysis for patients with IIH. A P value of 0.05 or less was considered to be statistically significant. RESULTS A total of 322 female patients with IIH and 400 female controls were included in the study. The mean age was 32.3 ± 10 years for patients with IIH and 33.9 ± 9 years for control patients (P = 0.03). The mean BMI was 35.0 ± 8 for patients with IIH and 26.7 ± 7 for control patients (P , 0.00001). Dissemination areas had a mean population of 1,525 ± 1801 residents. There was a significant difference in median income between dissemination areas resided by patients with IIH and control patients ($34640 vs $36685 CAD, P = 0.02). Assuming a purchasing power parity of $1.207 CAD per $1.000 USD in 2016 (9), this is equivalent to a difference of $28699 USD vs $30394 USD. There was also a significant difference in the rate of postsecondary degree attainment between IIH and control dissemination areas (57.7% vs 60.5%, P = 0.01). Both outcomes remained significant after adjusting for age (P = 0.04 and P = 0.01, respectively). There were no significant differences in the percentage of visible minorities (P = 0.48), percentage of immigrants (P = 0.86), knowledge of official languages (English or French) (P = 0.30), percentage of married individuals (P = 0.50), average household size (P = 0.62), or unemployment rate (P = 0.18). A summary of these outcomes is provided in Table 1. Linear regression analysis demonstrated no significant relationship between the median income in dissemination areas resided by patients with IIH and their BMI (P = 0.17, R2 = 0.008, Fig. 1). There was a weak but significant inverse relationship between the rate of postsecondary degree attainment in dissemination areas resided by patients with IIH and their BMI (P = 0.01, R2 = 0.02, Fig. 2). DISCUSSION Through our retrospective chart review of 322 patients with IIH and 400 controls, we found that patients with IIH resided in geographic areas with lower average levels of income (P = 0.02) and education (P = 0.01) than control patients. However, the mean difference was small with a $2045 CAD ($1694 USD) difference in income and a 2.8% difference in rates of postsecondary degree attainment. We also found no significant difference in outcomes related to minority status. Our findings contrast those from a recent and similar study by Brahma et al in Philadelphia, USA. (6). Their study found that women with IIH were significantly more likely to be Black or Hispanic than White. Their study also found a much higher effect size for income, with the rate of residence in low-income census tracts being 20% higher in Eshtiaghi et al: J Neuro-Ophthalmol 2023; 43: 197-201 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Original Contribution TABLE 1. Comparison of baseline demographics and socioeconomic variables of patients with IIH and control patients Variable Baseline demographics of patients Age (years) BMI Socioeconomic variables across dissemination areas Median income (CAD) Postsecondary degree attainment (%) Visible minorities (%) Immigrants (%) No knowledge of official languages (%) Married individuals (%) Average household size (no. of persons) Unemployment rate (%) Patients with IIH (n = 322) Control Patients (n = 400) 32.3 ± 10 35.0 ± 8 33.9 ± 9, *P = 0.03 26.7 ± 7, *P , 0.00001 $34640 ± 11,153 57.7 ± 14 43.1 ± 28 39.2 ± 17 3.3 ± 3 45.4 ± 14 2.7 ± 0.7 7.9 ± 4 $36685 ± 12,225, *P = 0.02 60.5 ± 15, *P = 0.01 41.6 ± 27, P = 0.48 39.0 ± 17, P = 0.86 3.6 ± 4, P = 0.30 46.1 ± 14, P = 0.50 2.7 ± 0.7, P = 0.62 7.5 ± 4, P = 0.18 *p-value , 0.05. BMI, body mass index; IIH, idiopathic intracranial hypertension. patients with IIH compared with controls. They also found that 20.6% of patients with IIH relied on Medicaid for health insurance, which was more than double the rate in controls (9.8%). In both studies, patients with IIH had a significantly higher BMI than control patients, in keeping with obesity being the major risk factor for the development of IIH. Brahma et al attributed at least some of the increased prevalence of obesity in IIH to lower income levels and the consumption of cheap, calorie-dense meals in food swamps (6). However, in our study, we found no association between average income levels and BMI in patients with IIH. An epidemiological study performed by Toronto Public Health in 2014 also found no signif- icant differences in obesity rates by income level among residents living in the city (10). These results may be unique to the universal health care system and greater accessibility of healthy food options (as determined by the modified Retail Food Environment Index) in Toronto, Canada (11,12). On the contrary, a study conducted by the Centers for Disease Control and Prevention in the United States maintained that obesity is linked to lower income levels among women (3). Our study found a weak but significant relationship between higher rates of postsecondary degree attainment in dissemination areas and lower mean BMI in patients with IIH (P = 0.01). It is possible that patients with higher levels of education may be more health conscious and motivated FIG. 1. Scatter plot demonstrating the relationship between the median income in dissemination areas resided by patients with IIH and their BMI. BMI, body mass index; IIH, idiopathic intracranial hypertension. Eshtiaghi et al: J Neuro-Ophthalmol 2023; 43: 197-201 199 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Original Contribution FIG. 2. Scatter plot demonstrating the relationship between the rate of postsecondary degree attainment in dissemination areas resided by patients with IIH and their BMI. BMI, body mass index; IIH, idiopathic intracranial hypertension. to maintain a healthy weight. Conversely, patients with lower levels of education may be at higher risk of elevated BMI and therefore disease incidence and progression. However, this conclusion should be approached with caution because a previous study by Toronto Public Health did not demonstrate a significant difference in obesity rates by education level in the city (10). Regardless, it is still essential to educate every patient with newly diagnosed IIH on the importance of losing weight because weight gain over the course of follow-up has been shown to predict poor visual outcomes (13). Given that the authors of our study are among the few neuro-ophthalmologists serving most of the Greater Toronto Area, strengths of our study include a large IIH patient database and standardization in IIH diagnoses across patients. Limitations of our study include the lack of individual patient-level data. Mean aggregate data from dissemination areas were used as surrogate markers for patients’ socioeconomic status. Although these dissemination areas were small with an average population of 1,525 in each geographic region, variability within these areas may not be reflected accurately by aggregate data. This is especially true for variables such as racial status, where the aggregate racial makeup may not reflect the actual race of patients with IIH. This limitation may explain why our study did not find a relationship between visible minority status and IIH, whereas the study by Brahma et al did (6). We also did not routinely collect data on the racial backgrounds of our patients and therefore did not include this individual-level data. In our study, the postal codes in patients’ electronic medical records were obtained near the time of IIH diagnosis, when most patients have just begun to experience symptoms. Thus, our results do not reflect the accumulated lifetime morbidity of patients living with chronic IIH. These patients with chronic 200 IIH may experience greater income loss and social struggles secondary to vision loss and symptom burden. Finally, future studies can explore other patient factors other than income and food availability that place patients at higher risk of obesity and consequently IIH incidence and progression. These factors may include but are not limited to psychological barriers (e.g., depression and motivation to exercise), genetic predispositions, and other medical conditions (e.g., hypothyroidism or polycystic ovarian syndrome) (14). STATEMENT OF AUTHORSHIP Conception and design: J. A. Micieli, A. Eshtiaghi, E. Margolin; Acquisition of data: A. Eshtiaghi; Analysis and interpretation of data: J. A. Micieli, A. Eshtiaghi, E. Margolin; Drafting the manuscript: J. A. Micieli, A. Eshtiaghi, E. Margolin; Revising the manuscript for intellectual content: J. A. Micieli, A. Eshtiaghi, E. Margolin; Final approval of the completed manuscript: J. A. Micieli, A. Eshtiaghi, E. Margolin. REFERENCES 1. Boyter E. Idiopathic intracranial hypertension. J Am Acad Physician Assist. 2019;32:30–35. 2. Ghaffari-Rafi A, Mehdizadeh R, Ko AWK, Ghaffari-Rafi S, LeonRojas J. Idiopathic intracranial hypertension in the United States: demographic and socioeconomic disparities. Front Neurol. 2020;11:869. 3. Ogden CL, Fakhouri TH, Carroll MD, Hales CM, Fryar CD, Li X, Freedman DS. Prevalence of obesity among adults, by household income and education—United States, 2011– 2014. MMWR Morb Mortal Wkly Rep. 2017;66:1369– 1373. 4. Sobal J, Stunkard AJ. 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