Longitudinal study in myotonic dystrophy type 2 regarding health-related quality of life, pain and fatigue

Longitudinal studies in myotonic dystrophy type 2 (DM2) regarding health-related quality of life (HRQoL) are scarce. This lack of information hinders effective patient counseling and management. We established a long-term natural history study to assess the impact of DM2 on various health dimensions, addressing the current scarcity of data on its natural course, with the aim of providing insights that enhance optimal patient care. Over a 13-year period, we examined HRQoL, pain, and fatigue in patients with DM2 in comparison to those with adult-onset DM1.
Between 2006 and 2008, all known patients with DM2 in the Netherlands were invited to complete baseline questionnaires. Age- and sex-matched patients with adult-onset DM1 were approached to participate. These genetically confirmed DM patients were re-approached for follow-up in 2019. Date of birth, sex, weight (kg), height (m) and medication were recorded. The date of death of all deceased patients was recorded. Baseline data of deceased patients or patients who did not consent again were not used.
SF-36 subscales were used to assess the different areas of functional impairment in daily life. All eight SF-36 scales were transformed into scores ranging from 0 to 100, with a lower score indicating worse functioning or more pain.
Pain intensity was assessed by using the McGill Pain Questionnaire (MPQ). Pain intensity was scored from 0 to 100 on a 100 mm horizontal visual analogue scale (VAS), where 0 indicates no pain and 100 the worst imaginable pain.
Fatigue was assessed using the Checklist Individual Strength (CIS-fatigue). Individual items were scored using a 7-point Likert scale, with higher scores indicating higher levels of fatigue. A cut-off score of 76 in the CIS, or a score of 35 or higher on the subjective fatigue subscale indicates severe fatigue.
Baseline characteristics and data on SF-36, MPQ and CIS-fatigue scores were available for analysis with SPSS. Normality of data was tested by the Kolmogorov-Smirnov test. Related-samples Wilcoxon signed-rank test, Mann-Whitney U tests and McNemar tests were applied, as appropriate. As most data was not distributed symmetrically, medians instead of means were used, and the Hodges-Lehmann location-shift estimate of the median group difference with 95% confidence interval was calculated. Spearman correlations were used to measure relationships between patient characteristics and outcome on the questionnaires. P-values below 0.05 were considered to be significant.