Long-term secular trends in dermatomyositis and polymyositis mortality in the USA from 1981 to 2020 according to underlying and multiple cause of death mortality data

Background People with dermatomyositis (DM) or polymyositis (PM) often die from cancer, pulmonary, cardiac complications, or infections. In such cases, DM or PM might not be designated as the underlying cause of death (UCD) for mortality tabulation. In this study, we investigated DM/PM mortality trends in the USA from 1981 to 2020 with respect to UCD and multiple causes of death (MCD) data. Methods We used the MCD data to identify all deaths with DM or PM mentioned anywhere on the death certificate and as the UCD in the USA from 1981–1982 to 2019–2020. We calculated age-adjusted mortality rates (AAMRs) and annual percentage changes (APCs) based on joinpoint regression analysis. Results We identified 12,249 (3985 with DM and 7097 with PM) and 23,608 (8264 with DM and 15,344 with PM) people who died between 1981 and 2020 according to the UCD and MCD data, respectively. For DM, the APC was − 6.7% (from 1981–1982 to 1985–1986), − 0.1% (from 1985–1986 to 2003–2004), and − 1.9% (from 2003–2004 to 2019–2020) according UCD and was − 1.2% (from 1981–1982 to 2003–2004), − 2.5% (from 2003–2004 to 2015–2016), and 2.8% (from 2015–2016 to 2019–2020) according MCD. For PM, the APC was 1.9% (from 1981–1982 to 1989–1990), − 2.3% (from 1989–1990 to 2005–2006), and − 5.2% (from 2005–2006 to 2019–2020) according UCD and was 1.3% (from 1981–1982 to 1991–1992) and − 4.1% (from 1991–1992 to 2019–2020) according MCD. Conclusion We identified two times as many DM/PM deaths using the MCD as those identified using the UCD. Similar downward DM/PM mortality trends were noted according to UCD and MCD. However, the year of significant decline in PM mortality was about 10 years earlier according to MCD than those according to UCD.