A 10-year study of mortality in a cohort of patients with myotonic dystrophy

Objective: To determine the age and causes of death as well as the predicto rs of survival in patients with myotonic dystrophy (DM). Methods: In a long itudinal study, a cohort of 367 patients with definite DM was followed for 10 years. Results: During the 10-year period, 75 of the 367 DM patients (20 %) died. The mean age at death (53.2 years, range 24 to 81) was similar for men and women. Among these 75 patients, 32 (43%) died of a respiratory pro blem, 15 (20%) of cardiovascular disease, 8 (11%) of a neoplasia, and 8 (11 %) died suddenly. The ratio of observed to expected deaths was significantl y increased to 56.6 (95% confidence interval [CI] 38.7 to 78.0) for respira tory diseases, 4.9 (95% CI 2.7 to 7.7) for cardiovascular diseases, and 2.5 (95% CI 1.1 to 4.6) for neoplasms. The mean age at death was 44.7 years fo r the childhood phenotype of DM, 47.8 years for the early-adult, 55.4 years for the adult, and 63.5 years for the mild phenotype (F = 4.8, p = 0.005). The age-adjusted risk of dying was 3.9 (95% CI 1.3 to 11.0) times greater for a patient with a distal weakness and 5.6 (95% CI 2.2 to 14.4) times gre ater for a patient with proximal weakness as compared with a person without limb weakness. Conclusions: Life expectancy is greatly reduced in DM patie nts, particularly in those with early onset of the disease and proximal mus cular involvement. The high mortality reflects an increase in death rates f rom respiratory diseases, cardiovascular diseases, neoplasms, and sudden de aths presumably from cardiac arrhythmias.