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Trends in the incidence and mortality of systemic lupus erythematosus, 1950-1992
K M Uramoto1, C J Michet, J Thumboo
1Mayo Clinic, Rochester, Minnesota 55905, USA.
Objective:
To describe trends in systemic lupus erythematosus (SLE) incidence and mortality over the past 4 decades.
Methods:
Using the Rochester Epidemiology Project resources, medical records were screened to identify all Rochester, Minnesota residents with any SLE-associated diagnoses, discoid lupus, positivity for antinuclear antibodies, and/or false-positive syphilis test results determined between January 1, 1980 and December 31, 1992. Medical records were then reviewed using a pretested data collection form in order to identify cases of SLE according to the American College of Rheumatology 1982 revised criteria for SLE. Drug-induced cases were excluded. All identified SLE patients were followed up until death, migration from the county, or October 1, 1997. These data were combined with similar data from the same community obtained between 1950 and 1979, and trends in the SLE incidence and mortality over time were calculated.
Results:
Of the 430 medical records reviewed, 48 newly diagnosed cases of SLE (42 women and 6 men) were identified between 1980 and 1992. The average incidence rate (age- and sex-adjusted to the 1970 US white population) was 5.56 per 100,000 (95% confidence interval [95% CI] 3.93-7.19), compared with an incidence of 1.51 (95% CI 0.85-2.17) in the 1950-1979 cohort. The age- and sex-adjusted prevalence rate as of January 1, 1993 was approximately 1.22 per 1,000 (95% CI 0.97-1.47). Survival among SLE patients was significantly worse than in the general population (P = 0.017 compared with the 1980-1992 cohort, and P < 0.0001 compared with the 1950-1979 cohort, by log-rank test). Cox proportional hazards modeling demonstrated a statistically significant improvement in the survival rate over time (P = 0.035).
Conclusion:
Over the past 4 decades, the incidence of SLE has nearly tripled, and there has been a statistically significant improvement in survival. These findings are likely due to a combination of improved recognition of mild disease and better approaches to therapy.