Headache pain intensity was assessed by an 11-point pain scale (0 10) with 0 indicating "no headache" and 10 indicating "headache as severe as I can imagine" [19].
The significant linear trend by headache status interaction indicated that headache days per wave changed differently for those with EM vs CM.
To record headache intensity, a 10-point verbal rating scale (VRS) was used, where 0 indicated no headache; 1 indicated a different sensation, pounding or throbbing, but not necessarily painful; 5 indicated moderate headache and 10 indicated worst imaginable headache [14].
Univariable and multivariable analyses indicated that headache aggravation by movement is an independent predictor of RLS among participants with TTH (Table 3).
However, epidemiological studies over 25 years have consistently indicated that headache disorders and anxiety and depression are excessively comorbid [2 20], with bidirectional [6] or syndromal [7] associations.
Qualitative interviews from a validity study [ 14] indicated that headache and backache often led to the use of medical services.
In contrast, only 15.2% of the non-migraine headache participants indicated that their headache had severe adverse impact to their daily life.
The main findings of the present study were that the logistic regressions indicated that the headache intensity and headache frequency were associated with onset of MOH and therefore could be factors to take into account to prevent the development of MOH.
