SLE Incidence Rates Rose in US for Past Four Decades
Mayo Clinic researchers examined trends in SLE incidence, prevalence, mortality
The incidence of systemic lupus erythematosus (SLE) has increased in the U.S. the past four decades, a recent study shows.
Study data also indicated the increased incidence seen during that time was significantly higher among racial and ethnic minority populations.
“As the US population grows more diverse, we might continue to see an increase in the incidence of SLE,” the researchers wrote.
The study “Rising incidence and prevalence of systemic lupus erythematosus: a population-based study over four decades” was published in the journal Annals of the Rheumatic Diseases.
SLE, the most common form of lupus, is an autoimmune disease that affects multiple organs and can manifest itself in a wide variety of ways.
This complexity has hindered estimates of its true incidence, as well as its prevalence, and mortality in the U.S. Prevalence is a measure of all disease cases, both new and preexisting, in a population within a specific period of time, while incidence comprises the number of new cases only.
According to estimates of five surveillance registries of the Centers for Disease Control and Prevention, SLE is more frequent in racial and ethnic minority populations compared with the white population. However, its true incidence remains unknown, with discrepancies being reported in different studies. Also, the majority of these studies were conducted over a short time period.
Now, a team led by researchers at the Mayo Clinic examined the trends in SLE incidence, prevalence, and mortality over a period of 43 years, and based on data from patients living in Olmsted County, Minnesota.
All clinically diagnosed cases of SLE recorded from 1976 to 2018 among residents of Olmsted County were identified using data from the population-based study Lupus Midwest Network (LUMEN), part of the Rochester Epidemiology Project (REP).
During this time, there was a total of 188 incident SLE cases in Olmsted County. Patients had a mean age of 46.3 years at diagnosis and 83% were female. The majority (82%) were non-Hispanic white, followed by non-Hispanic Asian (10%), non-Hispanic black (5%), and Hispanic (3%).
During the four decades, the proportion of females with SLE decreased from 93% to 78%, while that of males increased from 7% to 22%. Also, the percentage of non-Hispanic white patients decreased from 100% to 70% in the most recent decade.
All 188 patients met the SLE European Alliance of Associations for Rheumatology (EULAR)/American College of Rheumatology (ACR) classification criteria and all were positive for antinuclear antibodies (ANAs), a disease hallmark. ANAs are antibodies that wrongly recognize the body’s own proteins as foreign, mounting immune attacks against them.
The most common clinical manifestations included arthritis (54%), a reduction in the number of white blood cells (44%), and acute cutaneous lupus (21%).
Seven patients (4%) had lupus nephritis, a serious kidney condition commonly seen in people with SLE, confirmed by biopsy, and 15 (8%) had high levels of proteins in the urine. Neurologic manifestations were rare at diagnosis.
SLE incidence higher in females
After adjustments for age and sex, the overall incidence of SLE during the four decades was 4.77 per 100,000 people. Incidence was higher in females compared with males (7.58 female vs. 1.89 male per 100,000 people). This was specifically true in female patients ages 18–79 years.
The overall incidence rate of SLE increased from 3.32 during 1976–1988, to 6.44 during 2009–2018. Its overall incidence rate during 1999–2018 was significantly higher among racial and ethnic minority populations (8.17 per 100,000 people) compared with non-Hispanic whites (5.42 per 100,000 people).
No lessening of disease severity was seen during the four decades, as assessed by EULAR/ACR scores.
Prevalence also increased over the four decades, from 30.65 per 100,000 people in 1985 to 97.4 per 100,000 people in 2015. In females, SLE prevalence increased three times and in males four times.
During this period, the survival rate of SLE patients has remained lower than that of the general population, with no signs of improvement.
Overall, these findings suggest that both incidence and prevalence of SLE are rising in the U.S., which “may be at least partially explained by the rising ethnic/racial diversity of the population,” the researchers wrote.
According to the most recent U.S. census data, the proportion of non-Hispanic white people decreased from 63.7% in 2010 to 57.8% in 2020. Thus, these findings suggest that “that as the US population becomes more diverse, the incidence of SLE will continue increasing,” the authors wrote.