Two important studies presented at the American College of Rheumatology annual meeting held in San Diego, California from October 25-30, 2013 analyzed the prevalence of systemic lupus erythematosus (SLE) and lupus nephritis in the US population, as well as the impact of SLE on employment and work productivity in American workers. Prevalence estimates of SLE in the United States vary, ranging from 161,000 to 1.5 million. Lupus nephritis, the most common serious manifestation of SLE, is reported to develop in up to 67% of patients with SLE, but in the absence of population-based data, it has been difficult to estimate the burden of SLE and lupus nephritis in the United States.
Gandhi and colleagues (Abstract 1071) carried out a population-based analysis of patients from databases with more than 80 million Medicare and Medicaid enrollees; cases of SLE were defined as patients with a minimum of 3 SLE claims, based on International Classification of Diseases, Ninth Edition (ICD-9) codes, and cases of lupus nephritis were defined as patients requiring at least 2 visits to a nephrologist or at least 2 diagnoses of lupus nephritis based on ICD-9 codes within 12 months of being diagnosed with SLE.
Based on these data, the overall prevalence of SLE in the US population was projected to be 313,436 patients(100 per 100,000 persons), with the prevalence of lupus nephritis projected as 63,256 patients (20 per 100,000 persons). The prevalence rates of SLE and of lupus nephritis were highest between the ages of 18 and 64 years, and were greater in females (227 cases of SLE and 52 cases of lupus nephritis per 100,000 persons) than in males (102 cases of SLE and 22 cases of lupus nephritis per 100,000 persons).
The proportion of lupus nephritis in patients with SLE (approximately 20%) was significantly lower than what had been reported in cohort studies, suggesting that previous cohort studies enrolled a more severe subset of patients with SLE. Although only 15.1% of all US citizens were insured by Medicare as of 2009, 26.2% of patients with SLE were Medicare beneficiaries, although the majority of them (51.5%) were aged <65 years, indicating the considerable impact of disability associated with this disease.
Various factors influence the ability of patients with SLE to work, and their work productivity, including disease activity, cognitive impairment, comorbidities, education, and psychosocial factors. Sree and coworkers (Abstract 1006) presented 1- and 2-year longitudinal evaluations of data from the GOAL registry, a prospective cohort of patients with SLE from the Georgia Lupus Registry who are predominantly African American (77%) and their mean disease duration is 13.5 years.
Of 547 patients with SLE who were employed at disease diagnosis, 252 patients (49%) aged 18 to 64 years remained employed at 1 year. Age at diagnosis (P = .039), disease duration (P = .038), lower education attainment (P = .01), worse physical health (P = .002), and greater disease activity (P = .04) were significantly associated with work loss over 1 year, whereas living with a partner (ie, social support) tended to be a protective factor compared with patients who were single, widowed, or divorced (P = .09). Of note, work productivity over the 1-year period, as measured by the Work Productivity and Activity Impairment tool, was not significantly impacted by SLE disease activity.
These results suggest that efforts to maintain patients with SLE in the workforce should target younger persons with a recent SLE diagnosis, as well as those with poorer physical health and persons from vulnerable socioeconomic groups.