Prevalence of comorbidities in systemic sclerosis versus rheumatoid arthritis: a comparative, multicenter, matched-cohort study

BACKGROUND: Comorbidities are common in chronic systemic connective tissue diseases and are associated with adverse outcomes, increased morbidity and mortality. Although the prevalence of comorbidities has been well-studied in isolated diseases, comparative studies between different autoimmune diseases are limited. In this study, we compared the prevalence of common comorbidities between patients with systemic sclerosis (SSc) and patients with rheumatoid arthritis (RA). METHODS: Between 2016 and 2017, 408 consecutive patients with SSc, aged 59 ± 13 years (87% women), were matched 1:1 for age and gender with 408 patients with RA; mean disease duration was 10 ± 8 and 9 ± 8 years, respectively. Rates of cardiovascular risk factors, coronary artery disease, stroke, chronic obstructive pulmonary disease (COPD), osteoporosis, neoplasms and depression were compared between the two cohorts. RESULTS: The prevalence of dyslipidemia (18.4% vs 30.1%, p = 0.001) and diabetes mellitus (5.6% vs 11.8%, p = 0.007) and body mass index (p = 0.001) were lower in SSc compared to RA, while there was no difference in arterial hypertension or smoking. While there was a trend for lower prevalence of ischemic stroke in SSc than in RA (1.1% vs 3.2%, p = 0.085), coronary artery disease was comparable (2.7% vs 3.7%). No differences were found between patients with SSc and patients with RA in the prevalence of COPD (5.2% vs 3.7%), osteoporosis (24% vs 22%) or neoplasms overall (1.1% vs 1.7%); however lung cancer was the most prevalent cancer in SSc (7/17, 41%), whereas hematologic malignancies (7/19, 36%) and breast cancer (7/19, 36%) predominated in RA. Depression was more prevalent in SSc (22% vs 12%, p = 0.001), especially in diffuse SSc. CONCLUSIONS: Despite the prevalence of dyslipidemia and diabetes mellitus in SSc being almost half that in RA, the cardiovascular comorbidity burden appears to be similar in both. The overall prevalence of neoplasms is no higher in SSc than in RA, but SSc has a more negative impact on quality of life, as clearly, more SSc patients develop depression compared to patients with RA.