Associations between area-level socioeconomic disadvantage and COVID-19 disease consequences in Sydney, Australia: A retrospective cohort analysis

Background Socioeconomic disparities have shaped COVID-19 outcomes worldwide. Focusing on disease consequences once infected (severity among cases), we examined whether area-level socioeconomic disadvantage was associated with hospitalisation and death among COVID-19 cases in Greater Sydney, Australia.

We conducted a retrospective cohort study of confirmed and probable COVID-19 cases recorded in the New South Wales Notifiable Conditions Information Management System from 2 March 2020 to 21 February 2022. Area-level disadvantage was measured using the Index of Relative Socio-Economic Disadvantage (IRSD). We modelled the odds of (a) hospitalisation and (b) death conditional on infection using logistic regression, adjusting for age and gender.

Among 782,883 included cases, 3.5% were hospitalised and 0.2% died due to COVID-19. Greater area-level disadvantage (lower IRSD) was associated with higher odds of hospitalisation (adjusted odds ratio [AOR] 0.996 per IRSD point; 95% CI 0.996–0.996) and death (AOR 0.997; 95% CI 0.996–0.997), holding age and gender constant. For illustration, the difference between two Sydney postal areas with markedly different IRSD scores corresponds to several-fold differences in the odds of hospitalisation and death among cases.

Area-level socioeconomic disadvantage was associated with higher risks of hospitalisation and death among COVID-19 cases in Greater Sydney – a setting with public hospital care – indicating inequities in disease consequences once infected. Given the absence of individual-level comorbidity and vaccination data, the most plausible explanation is disparities in comorbidity and risk-factor burden, although contributions from differences in access to and quality of care cannot be ruled out. Public health responses should prioritise chronic-disease prevention and management in disadvantaged communities to mitigate inequitable outcomes in future pandemics. Competing Interest Statement The authors have declared no competing interest. Funding Statement Yes Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethics approval for the study was granted by the Sydney Local Health District Research Ethics and Governance Office on 11 December 2020 (Protocol No. X20-0467 and 2020/ETH02564). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes List of abbreviations - AOR - Adjusted odds ratio - EFHIA - Equity-focused health impact assessment ICU Intensive care unit - IRSD - Index of Relative Socio-Economic Disadvantage - NCIMS - Notifiable Conditions Information Management System NSW New South Wales - PCR - Polymerase chain reaction - SARS-CoV-2 - Severe acute respiratory syndrome coronavirus 2 - SEIFA - Socio-Economic Indexes for Areas - STROBE - Strengthening the Reporting of Observational Studies in Epidemiology