Authors also found that the mortality rate of people with cutaneous lupus erythematosus (CLE) are generally similar to that of the general population.
A new hyper-local analysis of cutaneous lupus erythematosus (CLE) incidence shows the number of cases of the disease has remained relatively stable over the past 4 decades.
Writing in Mayo Clinic Proceedings, the authors said the new study offers a comprehensive analysis of CLE trends, albeit one limited to a specific geographic area. They explained that CLE can be classified into 3 subgroup: acute CLE, subacute CLE (SCLE), and chronic CLE (CCLE). The former is typically associated with systemic lupus erythematosus (SLE), but the latter 2 may or may not appear alongside SLE.
Overall estimates of CLE incidence are estimated at 2.7 to 4.4 cases per 100,00 people, but the authors said those data leave several key issues unexplored. They noted that CLE can be associated with lifestyle factors, including smoking, which may have changed over time. There is also a lack of knowledge about how CLE affects mortality and a dearth of data related to CLE subgroups.
The study investigators also noted that in Olmsted County, Minnesota, where Mayo Clinic’s Rochester headquarters is located, there has been a recent rise in SLE incidence, something they attribute to the area’s increase in racial and ethnic diversity in recent years.
For all those reasons, the investigators decided to analyze lupus incidence data in Olmsted County to see whether they could identify changes or trends in CLE incidence.
They retrospectively examined all cases of CLE among Olmsted County residents between 1976 and 2018, using the Rochester Epidemiology Project, a medical records linkage system allowing for the review of medical records of patients from the area. In addition to examining incidence and prevalence of CLE generally, the authors looked at CLE subgroups.
Overall, the authors found an incidence rate of 3.9 per 100,000 (95% CI, 3.4-4.5). There were no significant trends across sexes or age groups during that time period. In terms of prevalence, the age- and sex-adjusted prevalence of CLE was 108.9 cases per 100,000 people on January 1, 2015, the authors said.
“Our results revealed no secular incidence trends except a notable increase in CLE incidence within the 1985-1990 period,” the authors wrote. They said it is unclear why CLE incidence seemed to spike in the late 1980s.
Although the overall incidence of CLE was largely stable, the clinical features of the disease did appear to shift, the investigators said.
They noted that the proportion of cases of discoid lupus erythematosus, a subtype of CCLE, declined, while the proportion of SCLE and tumid lupus (another subtype of CCLE) increased.
While smoking rates in Minnesota declined significantly over the study period, the authors said that did not seem to affect CLE rates.
“It is possible that the accumulated nature of cigarette smoking in the 1960s and 1970s contributed to persistently high CLE rates observed in later decades,” they wrote.
Alhough the proportions of certain subtypes changed, the authors said there were no observed changes in mortality over time. The standardized mortality ratio observed in the study was 1.23 (95% CI, 0.88-1.66), which was similar to that of the general population.
The investigators said the major limitation of their study was that it was focused on a single geographic area and thus may not be generalizable to other areas. In particular, they noted that their study population was predominantly White patients. On the other hand, they said their findings were strengthened by their access to the complete medical records for most patients in the area over a long period.
Hocaoğlu M, Davis MD, Osei-Onomah S-A, et al. Epidemiology of cutaneous lupus erythematosus among adults over four decades (1976-2018): a Lupus Midwest Network (lumen) study. Mayo Clinic Proceedings. Published online November 5, 2022. doi:10.1016/j.mayocp.2022.06.022