Health care disparities and bladder cancer mortality in the United States: A closer look at the social vulnerability index.
Authors: Haniff Shaniza , Lee Yu-Che , Chang Ko-Yun , Kagathur Santosh , Shive Gowda Ashwin , Isaac Dan 
Published: September 2024

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Background:
Bladder cancer is a significant public health concern, with various factors influencing mortality rates. The Social Vulnerability Index (SVI) measures community resilience to external health stresses. This study investigates the association between bladder cancer mortality (BCM) and county-level SVI in the United States (U.S.).
Methods:
Mortality data from U.S. counties were obtained from the Centers for Disease Control (CDC) and Prevention Wide-Ranging Online Data for Epidemiologic Research (WONDER) database from 2015 to 2019 using the International Classification of Diseases-10th Edition (Code C67). The CDC and Agency for Toxic Substances and Disease Registry (ATSDR) county-level SVI was used as a composite measure of social vulnerability. The SVI includes several U.S. census variables grouped into four themes: Socioeconomic Status (SES), Household Characteristics, Racial and Ethnic Minority Status, and Housing Type and Transportation. Vulnerable SES variables include individuals with incomes below 150% of the federal poverty line, unemployment, those with housing cost burdens, and those without high school diplomas or health insurance. Vulnerable household variables include seniors over 65 years, children under 17 years, disabled civilians, single-parent households, and those with limited English proficiency. SVI Quartiles (Q1 being the least vulnerable and Q4 the most vulnerable) were compared to assess their impact on BCM. Negative binomial regression models were used to estimate Incidence Rate Ratios (IRRs) with 95% Confidence Intervals (CIs) using SAS software.
Results:
From 2015 to 2019, a total of 82,994 people died from bladder cancer, and the age-adjusted mortality rate per 1,000,000 was 42.4. A higher SVI in intermediate vulnerability quartiles was associated with a higher risk of BCM (Q2 and Q3: IRR = 1.06; 95% CI = 1.01-1.10; p = 0.009) compared to the least vulnerable quartile, Q1. Vulnerable SES had an increased risk of BCM (Q2 and Q3: IRR = 1.07; 95% CI = 1.03-1.12; p < 0.001) compared to Q1. BCM was also increased in individuals with vulnerable household characteristics (Q2 and Q3: IRR = 1.06; 95% CI = 1.02-1.10; p = 0.004) compared to Q1. Q4 was not significant in comparison to Q1 for the groups mentioned above. Interestingly, Racial and Ethnic Minority Status (Hispanic, Latino, African American, etc.) was associated with lower BCM in Q2 and Q3 (IRR = 0.88; 95% CI = 0.84-0.92; p < 0.001) and Q4 (IRR = 0.77; 95% CI = 0.73-0.81; p < 0.001) compared to Q1. No significant mortality differences were observed among vulnerable Housing Types and Transportation.
Conclusions:
Bladder cancer mortality is linked to vulnerable socioeconomic and household characteristics, while racial and ethnic minority status correlates with decreased risk. Future targeted public health interventions are needed to reduce bladder cancer mortality in vulnerable populations.

Bladder cancer mortality and its association with social vulnerability quartiles.

Bladder Cancer Mortality

Characteristic

IRR

95% CI

p-value

Social Vulnerability Index

Q1
—
—

Q2&Q3
1.06
1.01, 1.10

0.009

Q4
0.98
0.93, 1.03
0.4

Socioeconomic Status

Q1
—
—

Q2&Q3
1.07
1.03, 1.12

<0.001

Q4
1.00
0.95, 1.05
>0.9

Household Characteristics

Q1
—
—

Q2&Q3
1.06
1.02, 1.10

0.004

Q4
1.05
1.00, 1.10
0.052

Racial & Ethnic Minority Status

Q1
—
—

Q2&Q3
0.88
0.84, 0.92

<0.001

Q4
0.77
0.73, 0.81

<0.001

Housing Type & Transportation

Q1
—
—

Q2&Q3
1.03
0.99, 1.08
0.2

Q4
0.98
0.93, 1.03
0.4

IRR = Incidence Rate Ratio, CI = Confidence Interval.