76 subjects (42 male, and 34 female) had 8 week follow-up data available at the time of this report. The mean age was 45.7 years, the median 46 years, and the range 12-79 years. The mean age of stiffness symptom onset was 13.7 years. Twenty-five subjects (32.9%) had sodium channel mutations, 27 (35.5%) chloride channel mutations, 5 (6.6%) DM2 mutations, and 19 (25.0%) had no mutations detected ().
Demographics. 76 subjects, 385 person-weeks recorded.
The 76 participants accounted for 385 person-weeks reported during the first 8 weeks after the baseline visit. Overall there were 5.07 calls per participant (63.4%). Forty-eight (63.2%) subjects called in 5 or more times, and 14 (18.4%) called in all 8 weeks (). Comparing compliance for weeks 5-8 (month 2) to compliance for weeks 1-4 (month 1) there was a median of 1 fewer calls per participant (Q1, Q3: 0, 2).
Number of weeks a call was recorded by the IVR system. Total number reporting 76. Forty-eight subjects called in 5 or more times (63.2%), and 14 called in 8 times (18.4% of the total population).
The weekly frequency of symptoms was: stiffness 344 (89.4%), weakness 243 (63.1%), tiredness 267 (69.4%), and pain 242(62.9%) (). Weekly reporting included the number of days for which each subject experienced a given symptom. The median numbers of days per week reported for each symptom were: stiffness 5 (Q1, Q3: 2, 7), weakness 2 (Q1, Q3: 0, 5), tiredness 3 (Q1, Q3: 0, 6), and pain 2 (Q1, Q3: 0, 7).
Figure 2 IVR—frequency and severity of reported symptoms. A. Weekly frequency of reported symptoms (n=76, total of 385 person-weeks recorded). Subjects were considered to have the given symptom if they answered yes to the first tier question whether they (more ...)
For each week a given symptom was reported, the patient was also asked to rate the severity of the symptom on a 1-9 scale. The median symptom severity for each symptom was: stiffness 4 (Q1, Q3: 2, 6), weakness 2 (Q1, Q3: 0, 5), tiredness 3 (Q1, Q3: 0, 5), and pain 3 (Q1, Q3: 0, 5). The mean symptom severity was stiffness 3.85, weakness 2.53, tiredness 2.85 and pain 2.68 (). shows the within-subject and between-subject standard deviation (SD) for symptom severity. The within-subject SDs were 1.50 for stiffness, 1.41 for weakness, 1.13 for tiredness, and 1.38 for pain. The between subject SDs were 1.82 for stiffness, 2.08 for weakness, 2.35 for tiredness, and 2.25 for pain. The within subject SD was less than the between subject SD for all symptoms reported.
Stratifying the study population by genetic mutation, there were significantly higher severity scores for tiredness and pain for DM2 compared to chloride channel mutations (). When tiredness severity scale was regressed on the genetic mutation the mean estimates were 4.71 for DM2 and 2.30 for chloride channel mutation (p = 0.04). When the dependent variable was pain, the mean estimates were 4.09 for DM2, and 1.71 for chloride channel mutation (p = 0.007). Of note, stiffness did not differ significantly in either severity or frequency by genetic subtype.
For subjects who had handgrip myotonia on clinical examination there was an average increase in the severity score for stiffness of 1.12 (p=0.02). For subjects who had warm-up on clinical examination there was an average increase in severity score for stiffness of 0.99 (p=0.03). There was no association between any symptom category on the IVR and eye closure myotonia, clinical measures of paramyotonia or electromyography myotonia grade for any muscle tested.