Rationale: Interstitial lung disease (ILD) represents a major challenge in systemic sclerosis (SSc), but there are no precise, population-based data on its overall impact, limiting opportunities for screening and management strategies. Objectives: Evaluate impact of ILD in a unique, nationwide, population-based SSc cohort. Methods: ILD was assessed prospectively in the Norwegian SSc (Nor-SSc) cohort, including all 815 patients with SSc resident in the country from 2000 to 2012. Lung high-resolution computed tomography (HRCT) scans were available for fibrosis quantification at baseline (n = 650, 80%) and follow-up. Pulmonary function tests were assessed at baseline (n = 703, 86%) and follow-up. Vital status and standardized mortality ratios (SMRs) were estimated at study end (2018) in the 630 incident Nor-SSc cases and 15 individually matched control subjects. Cumulative survival rates were computed. Measurements and Main Results: At baseline, 50% of the subjects with SSc (n = 324) had ILD by HRCT and 46% displayed pulmonary function declines consistent with ILD progression. Mortality correlated with extent of lung fibrosis as SMR increased from 2.2 with no fibrosis to 8.0 with greater than 25% fibrosis. SMR was inversely related to baseline FVC% and increased at all FVC levels below 100%. In patients with normal-range baseline FVC (80-100%), the 5and 10-year survival rates correlated with presence or absence of lung fibrosis, being 83% and 80%, respectively, with no fibrosis and 69% and 56%, respectively, with lung fibrosis (P = 0.03). Conclusions: The mere presence of ILD at baseline appears to affect outcome in SSc, suggesting that all patients with SSc should undergo a baseline pulmonary function test and lung HRCT screening to diagnose ILD early and tailor further management.

Our data indicate that the population prevalence of PM/DM in Caucasians is quite low, but underscores the complexity and severity of the disorders.

An estimated point prevalence of sIBM seven times higher than previously observed in Europe is reported. Our data show considerable diagnostic delay, a major challenge with new sIBM treatments in the pipeline.

The spine and hip BMD reduction of 6%-8% is similar to that found in a comparable population-based study performed in another area in Norway. Among the disease-related variables tested for, only the use of prednisolone was independently associated with BMD reduction. However, the BMD reduction measured in this study indicates that disease-related mechanisms are involved.

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