Patients with systemic sclerosis have about a 55% chance of dying from their disease. Specifically, more than half of systemic sclerosis deaths are caused by pulmonary fibrosis, pulmonary arterial hypertension, and heart-related problems that are attributable to the disease, according to an analysis of data from an international registry.
The findings were published in the October issue of the Annals of the Rheumatic Diseases.
The overall mortality from systemic sclerosis (SSc) remains high, wrote Dr. Anthony J. Tyndall of the department of rheumatology at the University of Basel (Switzerland) and colleagues. To identify the causes and predictors of death in SSc patients, the researchers reviewed data from 5,860 adults who were enrolled in the EULAR Scleroderma Trial and Research Database (EUSTAR) database between 2004 and 2008. In all, 284 deaths were reported during the study period. Complete data were available for 234 deaths via questionnaires completed by the medical centers that reported a death in an SSc patient (Ann. Rheum. Dis. 2010;69:1809-15).
More than half (55%) of the deaths were directly attributable to SSc. Another 41% of deaths were not related to SSc, and the cause of death was not known in the remaining 4%.
Pulmonary fibrosis was the most common cause of death in SSc deaths (19%), followed by pulmonary arterial hypertension (14%) and myocardial causes (14%). Most myocardial causes were attributed to arrhythmia. Another 4% of SSc deaths were caused by renal crises.
These findings contrast with data from other autoimmune diseases, such as systemic lupus erythematosus and rheumatoid arthritis, in which clinically overt myocardial infarctions are more common causes of death, the researchers noted.
The main causes of death that were not related to SSc were infections (33%), malignancies (31%), and cardiovascular causes (29%). However, 25% of the patients who died of non-SSc causes had SSc-related comorbidities that likely contributed to their deaths, the researchers noted. These comorbidities included pneumonia, sepsis, and gastrointestinal hemorrhage. If these cases were added to the deaths directly caused by SSc, “the disease-related death toll would be as high as 65%,” the researchers said.
The average age of patients entering the study was 57 years, and 80% were women.
After control for multiple variables, the independent predictors of death in SSc patients included proteinuria, pulmonary arterial hypertension (PAH), forced vital capacity (FVC) less than 80% of normal, shortness of breath on exertion, reduced diffusing capacity of the lung for carbon monoxide (DLCO), and older age at onset of SSc (defined by the first signs of Raynaud’s phenomenon and modified Rodnan skin scores).
Sex was not an independent predictor of death in this study, but the researchers said that the effect of sex can be accounted for by the other variables.
The study was limited by possible biases in the coding of death certificates, but the findings support data from previous studies showing PAH and pulmonary restriction as independent risk factors for mortality in SSc patients, the researchers noted.
“The EUSTAR figures presented here are useful in estimating the number of patients that need to be included in clinical trials that investigate survival as an end point,” they said.
The researchers had no financial conflicts to disclose. EUSTAR exists under the auspices of the EULAR Standing Committee for Clinical Affairs and is funded by a research grant from EULAR.