Patients with systemic lupus erythematosus (SLE) have an increased risk of comorbidity, and recent guidelines recommend monitoring risk factors and instituting preventive care for some conditions. However, “the incidence rates of [cardiovascular disease], stroke, end-stage renal failure, cancer and infection [have] not been previously studied from a community perspective in a large SLE population in the U.K.,” write Frances Rees, BMBS, MRCP(UK), and colleagues from the University of Nottingham in Nottingham, U.K., in their latest study.
Reese and colleagues sought to closely examine comorbidity and SLE. Using patient information from the U.K. Clinical Practice Research Datalink from 1999–2012, they calculated the incident rate ratios per 1,000 person years for six comorbidities: cardiovascular disease, stroke, end-stage renal failure, cancer, osteoporosis and infection. The results of this retrospective cohort study were published in the June 2016 issue of Arthritis Care & Research.
Investigators identified 7,732 prevalent cases of SLE and compared them with 28,079 controls matched by age, sex and practice. Incidence rate ratios were adjusted for baseline, age, body mass index, smoking status, alcohol intake, hypertension, hyperlipidemia, prednisolone use and other factors. Age- and sex-specific incidence rates were also calculated.
“The [incidence rates] of all six comorbidities were significantly higher in people with SLE compared with controls (P<0.001) and remained significant after adjustment for age, sex and other confounding variables,” write the authors. “The rate of infection remained significantly higher in people with SLE regardless of whether cases or controls with an infection prior to baseline were excluded (P<0.001).”
Researchers found that men with SLE had higher incidence rates of cardiovascular disease, stroke and cancer compared with women with SLE. Women with SLE had higher rates of infection and osteoporosis. With regard to osteoporosis, men had a much greater relative risk compared with their matched controls.
For every age group, people with SLE had a higher incidence rate of comorbidity than controls. Overall, age had a significant effect on comorbidity incidence rates, apart from infection and cancer. Patients with SLE in the younger age groups had greater relative risk of comorbidity when compared with controls.
For cardiovascular disease and stroke, investigators found an increased incident rate across all age groups. This finding may “be due to a combination of increased conventional risk factors for atherosclerosis … in conjunction with added risks caused by chronic inflammation, secondary antiphospholipid syndrome, renal failure, early menopause and long-term steroid use,” write the authors in their discussion. However, older people with SLE still had the greatest absolute risk of cardiovascular disease.
Investigators found that the incidence of end-stage renal failure actually reduced with age. “This may be because people with SLE who develop lupus nephritis and subsequently end-stage renal failure develop it early in the disease process,” write the authors.
In this study, patients with SLE also had an increased incidence rate of cancer, particularly for lung cancer, Hodgkin’s and non-Hodgkin’s lymphoma, and other hematologic malignancies.
Throughout their discussion, investigators note that clinicians should be aware of the increased risks for this patient population. They recommend monitoring and instituting primary prevention strategies in conjunction with good disease control. Patients should be encouraged to modify behavioral risk factors, such as smoking. Investigators also call for further research to refine primary prevention strategies and reduce the excess morbidity associated with SLE.
Rees F, Doherty M, Grainge M, et al. Burden of comorbidity in systemic lupus erythematosus in the U.K., 1999–2012. Arthritis Care Res (Hoboken). 2016 Jun;68(6):819–827. doi: 10.1002/acr.22751.