Mortality and causes of death of 344 Danish patients with systemic sclerosis (scleroderma)

To determine survival, mortality and causes of death in Danish patients with systemic sclerosis (scleroderma), and to analyse how these parameters are influenced by demographic variables and the extent of skin involvement.

A cohort of 344 patients with incident systemic sclerosis (SSc) after 1 January 1960 was retrospectively identified, representing 3716 patient-years of follow-up. The vital status at the end of the study ultimo 1996 was established by reviewing the clinical charts and by contacting the Danish Central Person Register. The causes of death were based on information obtained from the hospital charts and the autopsy reports (80%) and death certificates (20%). The extent of skin sclerosis was described by means of a two-subset model (limited and diffuse involvement) and a three-subset model (digital, extremity and truncal involvement) in all patients. Expected numbers of deaths were calculated by means of age- and sex-specific mortality rates of the general Danish population.

Crude mortality rates were 6.5 and 3.9%/yr, respectively, in men and women. The standardized mortality ratio (SMR) was 2.9 (95% CI 2.5-3.4) and was not significantly influenced by sex or age at disease onset. Mortality rates were significantly increased in patients with diffuse skin sclerosis (SMR 4.5, 95% CI 3.5-5.7) and patients under the age of 35 yr (SMR 13, 95% CI 2.7-37). Of the 160 patients who died during the study, 41 deaths (26%) were SSc related, accounting for one-third of the excess mortality.

We found a significantly increased mortality in patients with SSc, particularly in the subset of patients with diffuse skin sclerosis and in young patients. The excess mortality was due to an increase in both the SSc-related mortality and the unrelated mortality. However, all other subsets also had a significantly increased risk of death, mainly due to an increased risk of death due to causes unrelated to SSc, cancer among others. The fact that the unrelated mortality in SSc was found to be 2-fold increased suggests that the excess mortality that was classified as unrelated should more appropriately be termed indirectly SSc related.