Ambulatory capacity in Japanese patients with Duchenne muscular dystrophy

Few long-term cohort studies have addressed changes in the ambulatory capacity of patients with Duchenne muscular dystrophy (DMD), and no reports have evaluated the factors associated with ambulatory capacity in Japanese.

The longitudinal changes in 10-meter run/walk ability and associated factors were retrospectively investigated using general practice data. The factors associated with loss of this ability before the age of 10 years were explored by logistic regression analysis using parameters of genetic mutations, corticosteroid use, the manual muscle test (MMT), and the joint range of motion (ROM). Explanatory variables of MMT grade included hip flexors, knee flexors, and knee extensors; ROM included hip extension, knee extension, and ankle dorsiflexion.

Among 418 patients diagnosed with DMD, 145 patients underwent the 10-meter run/walk test between March 1999 and July 2015. The median age at loss of 10-meter walking ability was 10.4 (interquartile range: 9.2-11.3) years. The 10-meter run/walk speed began to decline 3 years before the loss of 10-meter walking ability, and the median was <1 m/s 1 year before the loss of 10-meter walking ability. MMT grade for knee flexors and ROM for hip and knee extension were identified as independent predictors. Based on the change over time of these three items, limitation of the hip extension ROM preceded knee flexor weakness and limitation of the knee extension ROM.

This knowledge can be used in optimizing rehabilitation programs and evaluating effect of treatment for DMD patients.