All-cause, cause-specific and age-specific standardised mortality ratios of patients with systemic lupus erythematosus in Ontario, Canada over 43 years (1971-2013)

Abstract

Background: Survival in systemic lupus erythematosus (SLE) has improved substantially in the last 50 years. The aim of the present study was to assess the evolution of the all-cause, cause-specific and age-specific standardised mortality ratios (SMRs) of patients with lupus in Ontario, Canada.

Patients and methods: Between 1971 and 2013, 1732 patients were followed in the Toronto Lupus Clinic. Causes of death were retrieved from death certificates, autopsy reports, hospital records or the records of the family physicians. They were categorised as atherosclerotic, infectious, malignancy, active lupus and others. For the calculation of the SMR (indirect standardisation method), data from the general population of Ontario, Canada were used (Statistics Canada).

Results: Two hundred and forty-nine patients (205 women) died (infections 24.5%, atherosclerosis 15.7%, active lupus 13.3%, malignancy 9.6%); mean age was 53.2±16.6 years and mean disease duration 15.2±11.7 years. The all-cause SMR was substantially decreased from the 1970s (13.5, 95% CI 8.6 to 18.5) to recent years (2.2, 95% CI 1.4 to 3.1). Similar trends were observed for atherosclerosis, infections and malignancies over time. The all-cause age-specific SMR was particularly high in younger (19-39 years old) patients (SMR=12.4, 95% CI 9.7 to 15.1) as compared with individuals older than 40 years (SMR=3.1, 95% CI 2.6 to 3.6). The cause-specific SMR was also higher in younger patients, particularly for infections and malignancies.

Conclusions: The all-cause and cause-specific SMR significantly decreased over time, likely reflecting the advances in the management of SLE and certain comorbidities. The all-cause and cause-specific SMR was particularly high for younger patients (<40 years old).

Keywords: causes of death; standardized mortality ratio; systemic lupus erythematosus.