Table 1

Summary of the factors assessed in this study and features of the corresponding questionnaires/tools

Assessed factor	Questionnaire	Construct/subscale	Items	Range/replies	Cronbach’s alpha
Fatigue	PedsQL MFS*	General fatigue subscale	6	0–100: higher score=less fatigue	0.90
Pain	Visual Analogue Scale†	N/A	1	0–10: higher score=more pain	N/A
Sleep difficulties	HBSC‡	In the last 6 months, how often have you had difficulties getting to sleep?	1	Rarely or never; about every month; about every week; more than once a week; about every day	N/A
o of days physically active	HBSC‡	Over the past 7 days, on how many days were you physically active for a total of at least 60 min per day?	1	0–7 days per week	N/A
Physical functioning	PedsQL GCS§	Physical functioning subscale	8	0–100: higher score=better functioning	0.89
Depressive symptoms	RCADS¶	Major depressive disorder subscale	10	0–30: higher score=more depressive symptoms	0.85
Anxiety	RCADS¶	Total anxiety subscale	37	0–111: higher score=more anxiety	0.94
Pain catastrophising	PCS-C**	N/A	13	0–52: higher score=more pain catastrophising	0.91
Emotional functioning	PedsQL GCS§	Emotional functioning subscale	5	0–100: higher score=better functioning	0.79
Pressure at school	HBSC‡	How pressured do you feel by the schoolwork you have to do?	1	Not at all; a little; quite some; a lot	N/A
Being bullied	HBSC‡	How often have you been bullied at school over the last couple of months?	1	Never; one or two times in the past month; two or three times a month; about once a week; a few times a week	N/A
Communication at home	HBSC‡	Communication at home subscale	4	1–5: higher score=better communication	0.80
Support at home	HBSC‡	Support at home subscale	4	1–7: higher score=more support at home	0.92
Support by friends	HBSC‡	Support from friends subscale	3 (8–11 years) or 4 (12–18 years old)	1–7: higher score=more support from friends	0.95
Social functioning	PedsQL GCS§	Social functioning subscale	5	0–100: higher score=better functioning	0.75
Member of a sports team or club	HBSC‡	Are you a member of a sport community or club?	1	Member; not a member	N/A
Screen time	HBSC‡	About how many hours a day do you usually watch television in your free time during week and weekend days? About how many hours a day do you usually play games on a computer or game console in your free time during week and weekend days?	4	None at all; about half an hour a day; about 1 hour a day; about 2 hours a day; about 3 hours a day; about 4 hours a day; about 5 hours a day; about 7 or more hours a day	0.75

*Adapted from Gordijn et al.15
†Adapted from Rosier et al.18
‡Adapted from Currie et al.19
§Adapted from Engelen et al.23
¶Adapted from Kösters et al.25
**Adapted from Crombez et al.26
GCS, General Core Scale; MFS, Multidimensional Fatigue Scale ; N/A, not available; PCS-C, Pain Catastrophising Scale for Children; RCADS, Revised Child Anxiety and Depression Scale.