Objective Recent data has shown that patients with lupus nephritis (LN) have increased mortality. However, no studies have been population based, and few compare mortality data in Systemic Lupus Erythematosus (SLE) patients with and without LN. The aim of our study was to investigate mortality in patients who does or does not develop LN in a population based cohort.

Methods Multiple sources were used to identify all SLE patients in Oslo during 1999–2009 who met 4 or more of the American College of Rheumatology (ACR) criteria. Follow up time was until 1 st January 2014. Presence of LN was defined by the ACR criteria. Standardised mortality ratio (SMR) was compared to observed deaths in a matched control population.

Results Of the 325 SLE patients included in this study, 98 (30%) developed LN. 75 patients (77%) had biopsy proven LN. A total of 56 deaths occurred during the study period, corresponding to an overall SMR for all SLE patients of 2,1 (95% confidence intervall (CI) 1,2 to 3,4). The SMR estimate for LN patients were 3,8 (95% CI: 2,1 to 6,2) and 1,7 (95% CI: 0,9 to 2,7) for non LN patients.

Conclusion LN is associated with increased mortality, however SLE patients who do not develop LN have a good overall prognosis with no significant higher mortality than the general population.