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Importance

Prior research conducted in private for-profit health care systems has suggested that social determinants of health (SDOH) play a role in adverse postoperative outcomes. Whether these findings translate to universal health care systems is unknown.

Objective

To quantify the association of SDOH with risk of 30-day mortality after scheduled inpatient surgery.

Design, Setting, and Participants

This cohort study was conducted in Ontario, Canada’s most populous province. The cohort included consecutive adult patients (aged ≥18 years) who were eligible for Ontario’s universal health insurance and underwent a scheduled inpatient surgical procedure between January 1, 2017, and December 31, 2023. Diagnostic and procedural, demographic, vital statistics, and other data were obtained from linked health administrative databases.

Exposures

SDOH including neighborhood income, immigration status, and migration recency.

Main Outcome and Measure

Death within 30 days of index surgery. Logistic regression models were used to estimate the adjusted and unadjusted odds ratios (AORs and ORs) of the association of each SDOH with 30-day mortality.

Results

Overall, 1 036 759 patients (median [IQR] age, 66 [56-74] years; 526 158 females [50.8%]) who underwent a range of scheduled inpatient surgical procedures were included. Of these patients, 1780 (0.9%) from the lowest-income areas died, as did 1307 (0.6%) from the highest-income areas. Patients from the lowest-income areas were at 52.0% increased odds of death (OR, 1.52; 95% CI, 1.42-1.64) compared with those from the highest-income areas. This association persisted with models partially adjusted for demographic and procedural factors (AOR, 1.54; 95% CI, 1.44-1.66) and fully adjusted for comorbidities (AOR, 1.43; 95% CI, 1.33-1.54). A dose-response association was demonstrated between neighborhood income and mortality, with odds of death increasing with diminishing income (eg, quintile 3 vs quintile 5: AOR, 1.18 [95% CI, 1.10-1.27]; quintile 2 vs quintile 5: AOR, 1.32 [95% CI, 1.22-1.42]). There was evidence of effect modification of the association between neighborhood income and mortality by procedure complexity (eg, effect estimate for quintile 4 and high complexity: –0.0776 [95% CI, –0.2722 to 0.1169]; P = .002). Immigrant and refugee status and recent migration (<5 years) demonstrated reduced odds of mortality in unadjusted analyses, but these associations diminished with risk adjustment.

Conclusions and Relevance

In this cohort study, residency in lowest-income neighborhood was associated with increased risk of postoperative mortality despite adjustment for patient, procedure, and hospital factors. Improving postoperative outcomes likely requires addressing underlying SDOH disparities.