Factors of importance for dynamic balance impairment and frequency of falls in individuals with myotonic dystrophy type 1 - a cross-sectional study - including reference values of Timed Up & Go, 10m walk and step test.

Patients with myotonic dystrophy type 1 suffer from gait difficulties including stumbles and falls. To identify factors of importance for balance impairment and fall-risk a mapping of functional balance was performed, in a cross-sectional study of 51 adults. Walking, balance, falls and muscle force were self-assessed and measured. Reference values of balance were established through measurements of 220 healthy subjects. Falls were more frequently observed in the patients who were more severely affected of muscle weakness than in mildly affected patients, p=0.014. The number of falls showed negative correlation with balance confidence (rs=-0.516, p<0.001). The ankle dorsiflexor force together with the time difference between comfortable and maximum speed in 10m-walk proved to be significant factors for fall frequency. A ten Newton muscle force decrease showed 15% increase in odds ratio for frequent falls. One-second increase in time difference between comfortable and maximum walking speed showed 42% increase in odds ratio for frequent falls. In conclusion, assessing the ankle muscle force and the time difference in different walking speeds is important to detect risk of falling. The activities-specific balance confidence score reflects the consequences of the muscle force decrease. Certain patient strategies to diminish risk of falling could be due.