All-cause and External-cause Mortality Disparities Among Australians in Same-Sex Relationships Before and After Marriage Equality: A Nationwide Cohort Study, 2011-2023
Melbourne Institute Working Paper No. 07/26
Date: May 2026
Author(s):
Abstract
Objective: To examine secular trends in mortality by sexual orientation in Australia. Methods: Using Australian Census-linked-mortality records (2011–2023), Cox proportional hazard models were used to estimate all-cause and external-cause mortality risk among adults in same-sex relationships (n=54,529) and different-sex relationships (n=7,923,328), separately by sex. Inverse probability weights balanced comparators on age, educational attainment, and household income. Results were stratified into periods before and after Australia’s 2017 legalisation of same-sex marriage. Results: Compared to those in different-sex relationships, females and males in same-sex relationships experienced elevated all-cause mortality risk [HR1.25 (95% CI 1.15;1.35) and HR1.24 (95%CI 1.16;1.31), respectively] and external-cause mortality risk [HR2.56 (95%CI 2.01;3.26) and HR1.96 (95%CI 1.64;2.71), respectively]. Inequalities in external-cause mortality risk declined following Marriage Equality among females (HR 3.40 → 2.04) and males (HR 2.01 → 1.93) in same-sex relationships, though remained significantly elevated in both periods. Conclusions: Australians in same-sex relationships experience elevated mortality risk relative to those in different-sex relationships, with inequalities persisting after marriage equality. Routine collection of sexual identity in the Australian Census would support ongoing monitoring of these disparities.