Differential Effects of Social Vulnerability Index Among Older and Younger Adults With Cancer

TL;DR

This study finds that social vulnerability and insurance status have stronger effects on cancer survival in younger adults compared to older adults.

Contribution

The study reveals age-specific differences in how social vulnerability and insurance status affect cancer mortality.

Findings

Higher social vulnerability index (SVI) is linked to increased mortality risk in cancer patients, especially younger adults.

Insurance status significantly affects survival outcomes in younger adults but not in older adults after adjusting for SVI.

The impact of SVI on mortality is stronger for younger adults with breast, prostate, and colorectal cancers.

Abstract

Social determinants of health, (e.g. social vulnerability index [SVI]), are associated with adverse cancer-related outcomes. Most cancer cases occur among older adults (≥65). Effects of SDOH may differ between older and younger adults. Our objective was to examine the role of SVI on all-cause mortality among adults with cancer in Alabama. We included adults (≥18) with incident breast, prostate, colorectal, or lung cancer between 1/1/2010 and 12/31/2019 from the Statewide Cancer Registry. The exposure was census tract-level SVI in quartiles. The outcome was overall survival (OS) from diagnosis to death or end of follow-up (12/31/2021). We performed Cox proportional hazards models to estimate associations adjusting for age, race, sex (if applicable), stage, census-tract rurality (Rural-Urban Commuting Area Code), and subtype (breast). We assessed interaction and stratified by age group at diagnosis (<65, ≥65). We further adjusted for insurance status. Living in higher SVI quartiles was associated with significantly higher hazard of mortality across all cancer types examined; this association was stronger for those <65 at diagnosis as interaction with age was significant for breast, prostate, and colorectal cancer (p-values: breast: 0.025; prostate: <0.001; colorectal: 0.031). Adjusting for insurance status, the association between SVI remained significant among older adults but not among younger adults. Insurance status had a stronger independent association with mortality among younger adults. These results indicate neighborhood-level SVI and individual-level insurance status may have greater negative effect on OS among younger adults whereas other unmeasured factors may affect OS in cancer among older adults.