ObjectiveThis study was undertaken to investigate the long-term survival rates and prognostic factors in patients with idiopathic inflammatory myopathies (IIMs) based on myositis-specific antibody (MSA) stratification.MethodsExactly 628 patients with an IIM were included. Kaplan-Meier survival curves, univariate, and multivariate Cox regression were used to analyze the outcomes and risk factors.ResultsThe cumulative 1-, 5-, and 10-year survival rates for IIM patients overall were 91.4%, 82.8%, and 75.6%, respectively. The survival rate in the MSA subset was significantly different (P < 0.001). The 1- and 10-year survival rates in the anti-melanoma differentiation-associated protein 5 (anti-MDA-5)-positive subgroup were 79.5% and 58.5%, respectively, which were the lowest among all subgroups. The 10-year survival rate of anti-signal recognition particle (anti-SRP)-positive patients was the highest (96.4%). Independent risk factors that impacted the long-term prognosis for IIM patients included rapidly progressive interstitial lung disease (RP-ILD), malignancy, and elevated serum ferritin levels (hazard ratio [HR] 17.47, 20.36, and 9.15, respectively, P < 0.01), whereas disease duration was a protective factor (HR 0.27, P = 0.003). Among these subsets, the strongest independent risk factor for death in the anti-MDA-5-positive subgroup was RP-ILD (HR 3.4, P = 0.017). Malignancy was an independent risk factor in the anti-aminoacyl-tRNA synthetase antibody-positive, anti-transcription intermediary factor 1 gamma-positive, and MSA-negative subgroups (HR 46.69, 6.65, and 4.48, respectively; P < 0.001). RP-ILD was also a risk factor in the prognosis of individuals in the MSA-negative subgroup (HR 72.28, P < 0.001).ConclusionDespite favorable overall survival in patients with IIM, the anti-MDA-5-positive subgroup had the highest mortality rate among all MSA subgroups, highlighting the distinctive prognosis for patients with different MSAs. RP-ILD and malignancy are the most common causes of death in IIM patients.