Table 4 Annual percent change (APC) of dermatomyositis and polymyositis mortality rates based on joinpoint regression analysis according to underlying cause of death (UCD) and multiple causes of death (MCD) in the USA by sex from 1981–1982 to 2019–2020

Dermatomyositis, both sexes

UCD

1981–1982 to 1985–1986

 − 6.7%

0.046

1985–1986 to 2003–2004

 − 0.1%

0.681

2003–2004 to 2019–2020

 − 0.1%

 < 0.001

MCD

1981–1982 to 2003–2004

 − 1.2%

 < 0.001

2003–2004 to 2015–2016

 − 2.5%

 < 0.001

2015–2016 to 2019–2020

2.8%

0.256

Dermatomyositis, males

UCD

1981–1982 to 2019–2020

 − 1.2%

 < 0.001

MCD

1981–1982 to 2019–2020

 − 1.9%

 < 0.001

Dermatomyositis, females

UCD

1981–1982 to 1989–1990

 − 3.6%

0.037

1989–1990 to 2003–2004

0.7%

0.448

2003–2004 to 2019–2020

 − 2.4%

0.001

MCD

1981–1982 to 2003–2004

 − 0.7%

0.021

2003–2004 to 2013–2014

 − 2.8%

0.048

2013–2014 to 2019–2020

0.4%

0.842

Polymyositis, both sexes

UCD

1981–1982 to 1989–1990

1.9%

0.105

1989–1990 to 2005–2006

 − 2.3%

 < 0.001

2005–2006 to 2019–2020

 − 5.2%

 < 0.001

MCD

1981–1982 to 1991–1992

1.3%

0.115

1991–1992 to 2019–2020

 − 4.1%

 < 0.001

Polymyositis, males

UCD

1981–1982 to 1999–2000

 − 0.7%

0.262

1999–2000 to 2019–2020

 − 4.6%

 < 0.001

MCD

1981–1982 to 1991–1992

0.3%

0.779

1991–1992 to 2019–2020

 − 4.3%

 < 0.001

Polymyositis, females

UCD

1981–1982 to 1999–2000

 − 0.3%

0.622

1999–2000 to 2019–2020

 − 4.7%

 < 0.001

MCD

1981–1982 to 1991–1992

1.9%

0.083

1991–1992 to 2019–2020

 − 4.0%

 < 0.001