Background/Purpose

Despite the significant improvement in survival rates of patients with systemic lupus erythematosus (SLE) over the last four decades, mortality rates have remained at least 3 times that of the general population. We have recently reported from our longitudinal cohort study that infection is responsible for almost half of all deaths in lupus within the first 5 years of disease, and for over a third of deaths overall.

The aim of this study was to examine the standardized mortality ratios (SMR) for all-cause and cause-specific deaths in SLE patients followed prospectively at a large lupus clinic between 1970 and 2012.

Methods

Primary causes of death were recorded and acquired from autopsy reports, discharge summaries, hospital notes, and death certificates and divided into 5 categories: active lupus, atherosclerosis-related, infection, malignancy and ‘other’, all as determined by the certifying clinician.  For determination of the SMRs, cause-of-death data for the general population (by age, sex and year) were extracted from official records of the relevant provincial registry. SMRs were calculated as the ratio of observed deaths in the SLE cohort to the age, sex and year-match in the general population for all-cause and causes due to infection, atherosclerosis and malignancy.

SMRs were modelled using Poisson regression with the log of the expected number of events as an offset, and adjusted for age, sex, disease duration and decade of death.

Results

Of 259 patients known to have died, causes of death were established in 198 cases. Mean disease duration to time of death was 15.0 ± 11.3 years. Sixty-eight deaths were attributable to infection, 44 to atherosclerosis, 23 to malignancy and 39 due to active lupus.

For deaths due to all causes, the SMR falls significantly for the succeeding decade, from 12.02 (CI 7.67 – 18.82) for a female with < 5 years of SLE in the 1970s to 5.08 (CI 2.18 – 11.87) in the 2000s (p < 0.0001), with a similar decrease in those with SLE > 5 years.

For infection, there is a significant decade-on-decade reduction in the SMR, from 188 (CI 86 – 409) in the 1970s, to 117 (CI 42 – 324) in the 1980s, 73 (CI 21 – 256) in the 1990s and 46 (CI 10 – 203) in the 2000s (p < 0.0001), regardless of disease duration.

The SMRs for atherosclerosis and malignancy have also decreased over the 4 decades, from 14.09 (CI 9.99 – 16.86) and 1.79 (CI 1.12 – 2.87) in the 1970s, respectively, to 6.43 (CI 1.63 – 13.16) and 1.3 (CI 0.2 – 8.57) (p > 0.05).

Conclusion

Infection is the dominant cause of death in SLE, despite significant decreases in SMR over the last 40 years. Its prevalence as a cause-of-death is 40 times that of the general population. While primary prevention of cardiovascular disease should continue to be targeted in SLE, improvement in strategies to prevent and adequately treat infection in SLE require prioritisation.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/standardized-mortality-ratios-for-cause-specific-deaths-in-lupus-patients-followed-prospectively-at-a-single-centre-lupus-clinic/