Construction of a migraine-tension-type-index
tension-type headache, Migraine tension-type headache, phonophobia, headache, migraine, photophobia
MIGRAINE, TENSION-TYPE HEADACHE, APPENDIX
For the six variables related to severity, we observed only very moderate correlations (“Appendix A factor analysis suggested to reduce the severity variables to two factors: one factor related to all variables except frequency, and another factor related to frequency and length of episode (“Appendix This is in line with the distinction between migraine and tension-type headache, where intensity plays a major role, whereas the role of frequency is less clear. To compute the first summary variable (severity score), we applied a principal component analysis (PCA) based on the severity variables except frequency and length of episode (i.e. intensity, duration of headache prior to entering the project, the use of medicine, and the number of days absent from school), and obtained the weights indicated in Fig. Migraine-tension-type index. Footnote: The severity score was computed as 0.527 * intensity + 0.477 * duration + 0.433 * medication + 0.554 * sick days after rescaling the single variables to mean 0 and standard deviation 1The four co-occurring symptoms nausea, vomiting, phonophobia and photophobia tended to be rather distinctly associated (ORs between 1.8 and 43.2, see “Appendix We observed a distinct association between the severity score and the symptom score (r = 0.45), which supports the assumption that the distinction between migraine and tension-type headache using severity and co-occurring symptoms is as reasonable in children as in adults. We therefore defined a migraine-tension-type-index as a PCA-based summary score based on both the severity and the symptom scores.This new index describes a continuous spectrum and not just two distinct groups, but probably with migraine in the high end of the index and tension-type headache in the low end. This is supported by the distribution of the index in the three diagnostic subgroups (Fig. Migraine-tension-type index distribution in diagnostic subgroupsInterestingly, the non-classifiable children do not just constitute a distinct in-between-group, but partially include children with rather low or high index values.One advantage of this index is the possibility to include all children in investigations of the relation between the migraine-tension-type distinction and other variables.Figure Migraine tension-type headache index associations with headache characteristics