Importance: Life expectancy is greatly shortened in patients presenting with myotonic dystrophy type 1 (DM1), the most common neuromuscular disease. A reliable prediction of survival in patients with DM1 is critically important to plan personalized health supervision.
Objective: To develop and validate a prognostic score to predict 10-year survival in patients with DM1.
Design, setting, and participants: In this longitudinal cohort study, between January 2000 and November 2014, we enrolled 1296 adults referred to 4 tertiary neuromuscular centers in France for management of genetically proven DM1, including 1066 patients in the derivation cohort and 230 in the validation cohort. Data were analyzed from December 2016 to March 2017.
Main outcomes and measures: Factors associated with survival by multiple variable Cox modeling, including 95% confidence intervals, and development of a predictive score validated internally and externally. Mean values are reported with their standard deviations.
Results: Of the 1296 included patients, 670 (51.7%) were women, and the mean (SD) age was 39.8 (13.7) years. Among the 1066 patients (82.3%) in the derivation cohort, 241 (22.6%) died over a median (interquartile range) follow-up of 11.7 (7.7-14.3) years. Age, diabetes, need for support when walking, heart rate, systolic blood pressure, first-degree atrioventricular block, bundle-branch block, and lung vital capacity were associated with death. Simplified score points were attributed to each predictor, and adding these points yielded scores between 0 and 20, with 0 indicating the lowest and 20 the highest risk of death. The 10-year survival rate was 96.6% (95% CI, 94.4-98.9) in the group with 0 to 4 points, 92.2% (95% CI, 88.8-95.6) in the group with 5 to 7 points, 80.7% (95% CI, 75.4-86.1) in the group with 8 to 10 points, 57.9% (95% CI, 49.2-66.6) in the group with 11 to 13 points, and 19.4% (95% CI, 8.6-30.1) in the group with 14 points or more. In 230 patients (17.7%) included in the validation cohort, the 10-year survival rates for the groups with 0 to 4, 5 to 7, 8 to 10, 11 to 13, and 14 points or more were 99.3% (95% CI, 95.0-100), 80.6% (95% CI, 67.1-96.7), 79.3% (95% CI, 66.2-95.1), 43.2% (95% CI, 28.2-66.1), and 21.6% (95% CI, 10.0-46.8), respectively. The calibration curves did not deviate from the reference line. The C index was 0.753 (95% CI, 0.722-0.785) in the derivation cohort and 0.806 (95% CI, 0.758-0.855) in the validation cohort.
Conclusions and relevance: The DM1 prognostic score is associated with long-term survival.