Mortality and causes of death in systemic lupus erythematosus in New Zealand: a population-based study

This study aims to assess the mortality of systemic lupus erythematosus (SLE) patients and examine whether there are variations by subgroup.

SLE patients from 2005 to 2021 were identified from the national administrative datasets. The underlying causes of death were examined. Standardized mortality ratio (SMR) was estimated to compare the relative rate of observed deaths in SLE patients with expected deaths in the general population. The hazard ratios (HR) and 95% confidence intervals (CI) of all-cause mortality and SLE specific mortality by ethnicity were estimated after adjustment for age using a Cox proportional hazards model.

Of the 2802 patients included for analysis, 699 (24.9%) died with 209 (29.9%) SLE deaths. The age-standardized mortality rate of SLE was 0.29 per 100 000 for women and 0.05 for men. The mean age at death was 65.3 (17.1) years. Younger patients were more likely to have SLE as the underlying cause of death, from 78.9% for those under 20 years old to 18.7% for those aged 70-79 years. Compared with the general population, SLE patients were four times more likely to die (SMR: 4.0; 95% CI: 3.7, 4.3). Young patients had higher SMRs than older patients. Māori had worse all-cause mortality (HR: 1.72; 95% CI: 1.10, 2.67) and SLE specific mortality (HR: 2.60; 95% CI: 1.29, 5.24) than others.

The outcomes of SLE in New Zealand were still very poor compared with the general population. Māori with SLE had worse survival than others. Further research is needed to identify the reasons for this disparity.