LAUSR

Sir, Most systemic connective tissue diseases (CTDs) have been associated with increased all-cause mortality; hence, knowledge of the causes of death is fundamental in order to develop strategies aimed at reducing mortality. Limited data are available on the mortality profile related to the spectrum of CTDs. Since there has been an uptrend in overall mortality from CTDs in Brazil, data concerning the characteristics of CTDs are anticipated. In this database study of deaths that occurred within the general population of the State of Rio de Janeiro, Brazil, from 2006 to 2018, we sought to: (a) determine the main associated causes of death when a CTD was reported on the death certificate as the primary or underlying cause of death (UCD); and (b) compare the mortality profile of patients with CTDs with that of the ‘controls’, i.e. individuals from the same population in whom the UCD was not attributed to a CTD (non-CTD group). Anonymized death records coded according to the International Classification of Diseases, 10th revision (ICD-10) were provided by the local vital statistics department (Supplementary Table 1). Differences between proportions were compared using the chi-square or Fisher’s exact test, and those between continuous variables were compared using the Mann–Whitney test. During the study period, 2200 death certificates had a CTD (ICD-10 codes: M30–M36) listed as the UCD. Among those, women’s deaths (n1⁄4 1823) occurred at a younger age compared to men’s (n1⁄4 377) (median (interquartile range) 50 years (37–64) vs. 60 years (43–73.5); P< 0.0001). The main ICD-10 disease categories mentioned were systemic lupus erythematosus (SLE), necrotising vasculopathies, systemic sclerosis (SSc) and dermatopolymyositis (51%, 21.2%, 14% and 5.3% of patients, respectively (other CTDs 8.4%)). Considering the 2200 deceased with CTDs (2006–2018 period), infections were then reported in 53.7% of the death certificates, followed by circulatory (37.4%) and respiratory (30.3%) system disorders (Table 1). Compared with the deceased controls, patients of all age groups with CTDs (excluding those younger than one year of age) were more prone to complicate with infectious, genitourinary and blood-related disorders, in addition to cardiorespiratory (at 1– 59 years), endocrine (at 1–19 years) and digestive disturbances (at 1–19 years). Mortality associated with each of these conditions was highest among those aged 1–19 years (Table 1). On the other hand, CTD deaths were infrequently associated with cancer (n1⁄4 36) and neurological diseases (n1⁄4 69) (odds ratio (OR) 0.08, 95% confidence interval (CI) 0.06–0.12 and OR 0.74, 95% CI 0.58–0.94, respectively). Except for digestive system diseases (P1⁄4 0.07), meaningful differences in the mortality profile were found when comparing individual CTDs (Figure 1). Infections were most prevalent among patients with dermatopolymyositis (69.2%), whereas blood-related (11.4%) and genitourinary (34.7%) conditions were most common among those with SLE. Necrotising vasculopathy-related cases were more often complicated with endocrine (25.7%) and circulatory (45.8%) disorders, while patients with SSc and dermatopolymyositis had a higher burden of respiratory diseases (47% and 48%, respectively; P1⁄4 0.91). In conclusion, actions in our region are needed to attenuate the high mortality burden associated with infections (e.g. appropriate immunisations), besides improving the management of CTD-related comorbidities and inflammatory complications.