Neighborhood deprivation on increasing deficit accumulation in older breast cancer survivors and noncancer control individuals

<h4>Background</h4>Neighborhood characteristics can affect aging and health. We tested the effects of neighborhood deprivation on deficit accumulation frailty scores in a prospective cohort of breast cancer survivors vs control individuals aged 60 to 98 years.<h4>Methods</h4>Newly diagnosed, nonmetastatic breast cancer survivors (n = 477) and frequency-matched control individuals (n = 434) were enrolled between 2010 and 2023, with up to 5-year follow-up through 2024. Deficit accumulation was measured using a 48-item index (scores of 0-1); a clinically meaningful deficit increase was defined by a 0.06 score increase. Neighborhood deprivation was assessed using the Area Deprivation Index (ADI) at enrollment census block group and categorized into tertiles. Cause-specific Cox models tested the association between ADI and risk of deficit accumulation increase.<h4>Results</h4>Participants living in more deprived areas (second and third tertiles of ADI) had a higher risk of increased deficit accumulation (adjusted hazard ratios = 1.38, 95% CI =  1.01 to 1.89, P = .04 and 1.46, 95% CI = 1.07 to 1.94, P = .01 vs first tertile, respectively). Independent of ADI, being a survivor (vs a control individual) was associated with greater risk of increased deficit accumulation (adjusted hazard ratio = 1.69, 95% CI = 1.32 to 2.17, P < .001). Patterns of cumulative incidence rates of increased deficit accumulation differed by ADI: Survivors treated with chemotherapy (with or without hormone therapy) living in more vs less deprived areas had a 20% higher incidence of increased deficit accumulation within 1 year (P = .004), while survivors receiving hormone therapy alone and noncancer control individuals had their most pronounced differences by 4 years (10%, P = .32 and 10%, P = .05, respectively).<h4>Conclusions</h4>Neighborhood deprivation may increase deficit accumulation, with an apparent acceleration of effects among older (≥60 years of age) breast cancer survivors treated with chemotherapy.