Temporal trends in mortality in patients with systemic lupus erythematosus: a Danish population-based matched cohort study

Objective
Excess mortality has been demonstrated in patients with SLE compared with the general population. We aimed to investigate the 5-year and 10-year all-cause mortality in patients with SLE compared with the general population in recent decades.

Methods
This was a Danish nationwide population-based exposure-matched cohort study. Incident cases of SLE diagnosed between 1996 and 2015 were identified using administrative health registries and followed until 2020, allowing for 5 and 10 years of follow-up. Patients with SLE were matched 1:5 on age and sex with individuals from the Danish general population. Time-to-event analyses were performed using the pseudo-observation approach.

Results
In total, 1351 incident cases of SLE and 6755 matched controls were identified. The crude risk difference (RD) for 5-year mortality decreased over the study period, from 10.3% (95% CI 6.5–14.1%) to 4.6% (95% CI 1.4–7.8%) for patients with SLE compared with controls. The relative risk (RR) for 5-year mortality decreased similarly in the same period. Adjustment for comorbidities revealed lower RD and RR for mortality in patients with SLE compared with controls, but the decreasing trend remained. The crude and adjusted RD and RR for 10-year mortality did not change over the calendar period. The 10-year RR was highest in young patients with SLE (<50 years of age).

Conclusion
The 5-year mortality risk decreased over time for both patients with SLE and matched controls. However, excess 5-year mortality for patients with SLE in the most recent calendar period and excess mortality late in their disease course remained. Continued focus on preventing disease progression and comorbidity is required.