Supplemental Digital Content 1. Search strategies for each database

PubMed

((("Headache"[Mesh] OR "Headache Disorders"[Mesh] OR "Migraine Disorders"[Mesh] OR HEADACHE*[TIAB] OR "HEAD ACHE"[TIAB] OR MIGRAINE*[TIAB] OR CEPHALGI*[TIAB] OR CEPHALALGI*[TIAB] OR "FUNCTIONAL ABDOMINAL PAIN"[TIAB]) OR ((("Pain"[Mesh] OR PAIN*[TIAB] OR ACHE*[TIAB]) OR ("Myofascial Pain Syndromes"[Mesh] OR "Temporomandibular Joint Dysfunction Syndrome"[Mesh]) OR ("Back Pain"[Mesh] OR "Low Back Pain"[Mesh] OR "Neck Pain"[Mesh] OR "Shoulder Pain"[Mesh] OR "Abdominal Pain"[Mesh]) OR (BACKACHE[TIAB] OR "BACK-ACHE"[TIAB] OR BACKACHES[TIAB] OR "BACK-ACHES"[TIAB])) AND (CHRONIC*[TIAB] OR RECURR*[TIAB] OR PERSIST*[TIAB] OR FREQUENT*[TIAB])) OR (("Irritable Bowel Syndrome"[Mesh] OR "Irritable Bowel Syndrome") AND (PAIN*[TIAB] OR ACHE*[TIAB])) OR ("Arthralgia"[Mesh] OR "Fibromyalgia"[Mesh]) OR (Polyarthralgia[TIAB] OR ARTHRALGIA[TIAB] OR FIBROMYALGIA[TIAB] OR "Dysmenorrhea"[Mesh] OR DYSMENORRH*[TIAB]) OR ("Neuralgia"[Mesh] OR NEURALGI*[TIAB])) AND (CHILD OR CHILDREN OR ADOLESCENT OR ADOLESCENTS OR ADOLESCENCE OR TEEN* OR YOUTH* OR YOUNG)) AND ((risk*[Title/Abstract] OR risk*[MeSH:noexp] OR risk *[MeSH:noexp] OR cohort studies[MeSH Terms] OR (between AND group*[Text Word]))  OR (incidence[MeSH:noexp] OR mortality[MeSH Terms] OR follow up studies[MeSH:noexp] OR prognos*[Text Word] OR predict*[Text Word] OR course*[Text Word]))

Embase

chronic*:ab,ti OR recurr*:ab,ti OR persist*:ab,ti OR frequent*:ab,ti AND ('pain'/exp OR 'myofascial pain'/exp OR pain*:ab,ti OR ache*:ab,ti) OR 'headache'/exp OR 'headache and facial pain'/exp OR 'migraine'/exp OR headache*:ab,ti OR head NEXT/1 ache* OR migraine*:ab,ti OR cephalgi*:ab,ti OR cephalalgi*:ab,ti OR 'functional abdominal pain':ab,ti OR ('irritable bowel syndrome'/exp OR 'irritable bowel syndrome' AND (pain* OR ache*)) OR 'irritable colon'/exp OR 'arthralgia'/exp OR 'fibromyalgia'/exp OR polyarthralgia:ab,ti OR arthralgia:ab,ti OR fibromyalgia:ab,ti OR dysmenorrh*:ab,ti OR 'dysmenorrhea'/exp OR 'neuralgia'/exp OR neuralgi*:ab,ti AND ('child'/exp OR child OR 'children'/exp OR children OR 'adolescent'/exp OR adolescent OR adolescents OR 'adolescence'/exp OR adolescence OR teen* OR youth* OR young) AND ('incidence'/exp OR 'mortality'/exp OR 'follow up'/exp OR prognos* OR predict* OR course* OR 'risk'/exp OR 'cohort analysis'/exp OR risk*:ab,ti OR between NEXT/1 group*)

CINAHL

# Query S35 S24 and S34

S34 S28 or S33

S33 S29 or S30 or S31 or S32

S32 prognos* or predict* or course*

S31 (MH "Prospective Studies+")

S30 (MH "Mortality+")

S29 (MH "Incidence")

S28 S25 or S26 or S27

S27 TI between N5 group* or AB between N5 group*

S26 (MH "Prospective Studies") OR (MH "Case Control Studies")

S25 risk*

S24 S22 and S23

S23

( CHILD OR CHILDREN OR ADOLESCENT OR ADOLESCENTS OR ADOLESCENCE OR TEEN* OR YOUTH* OR YOUNG ) or ( CHILD OR CHILDREN OR ADOLESCENT OR ADOLESCENTS OR ADOLESCENCE OR TEEN* OR YOUTH* OR YOUNG )

S22 S7 or S8 or S9 or S10 or S11 or S15 or S16 or S17 or S18 or S19 or S20 or S21

S21 TI NEURALGI* or AB NEURALGI*

S20 (MH "Neuralgia+")

S19 (MH "Dysmenorrhea")

S18

TI ( Polyarthralgia OR ARTHRALGIA OR FIBROMYALGIA OR DYSMENORRH* ) or AB ( Polyarthralgia OR ARTHRALGIA OR FIBROMYALGIA OR DYSMENORRH* )

S17 (MH "Fibromyalgia")

S16 (MH "Arthralgia+")

S15 S2 and S14

S14 S12 or S13

S13 TI "Irritable Bowel Syndrome" or AB "Irritable Bowel Syndrome"

S12 (MH "Irritable Bowel Syndrome")

S11

TI ( MIGRAINE* OR CEPHALGI* OR CEPHALALGI* OR “FUNCTIONAL ABDOMINAL PAIN” ) or TI ( MIGRAINE* OR CEPHALGI* OR CEPHALALGI* OR “FUNCTIONAL ABDOMINAL PAIN” )

S10 TI ( HEADACHE* OR "HEAD ACHE" ) or AB ( HEADACHE* OR "HEAD ACHE" )

S9 (MH "Tension Headache") OR (MH "Migraine")

S8 (MH "Vascular Headache+") OR (MH "Tension Headache") OR (MH "Rebound Headache") OR (MH "Cluster Headache") OR (MH "Headache+")

S7 S5 and S6 S6 S1 or S2 or S3 or S4

S5 TI ( CHRONIC* OR RECURR* OR PERSIST* OR FREQUENT* ) or AB ( CHRONIC* OR RECURR* OR PERSIST* OR FREQUENT* )

S4 (MH "Temporomandibular Joint Syndrome") OR (MH "Myofascial Pain Syndromes+")

S3 TI ( BACKACHE OR “BACK-ACHE” OR BACKACHES OR “BACK-ACHES” ) or AB ( BACKACHE OR “BACK-ACHE” OR BACKACHES OR “BACK-ACHES” )

S2 TI ( PAIN* OR ACHE* ) or AB ( PAIN* OR ACHE* ) S1 (MH "Pain+")

PsychINFO

ID Search Terms S68 S54 and S63 and S67 S67 S42 or S66 S66 S43 or S44 or S48 or S49 or S50 or S51 or S52 or S53 or S65 S65 TI ( HEADACHE* OR "HEAD ACHE" ) or AB ( HEADACHE* OR "HEAD ACHE" ) S64 S56 and S63 S63 S57 or S58 or S59 or S60 or S61 or S62 S62 DE "Followup Studies" S61 TX incidence or mortality or prognos* or predict* or course* S60 TX cohort N1 stud* S59 TX between N5 group* or TX risk* S58 DE "Cohort Analysis" OR DE "Longitudinal Studies" S57 DE "Risk Assessment" OR DE "Risk Factors" S56 S54 and S55 S55 S42 or S43 or S48 or S49 or S50 or S51 or S52 or S53 S54 CHILD OR CHILDREN OR ADOLESCENT OR ADOLESCENTS OR ADOLESCENCE

OR TEEN* OR YOUTH* OR YOUNG S53 TI NEURALGI* or AB NEURALGI* S52 DE "Neuralgia" S51 DE "Dysmenorrhea" 

S50 TI ( Polyarthralgia OR ARTHRALGIA OR FIBROMYALGIA OR DYSMENORRH* ) or AB ( Polyarthralgia OR ARTHRALGIA OR FIBROMYALGIA OR DYSMENORRH* ) 

S49 DE "Fibromyalgia" S48 S36 and S47 S47 S45 or S46 S46 TI "Irritable Bowel Syndrome" or AB "Irritable Bowel Syndrome" S45 DE "Irritable Bowel Syndrome" 

S44TI ( MIGRAINE* OR CEPHALGI* OR CEPHALALGI* OR “FUNCTIONAL ABDOMINAL PAIN” ) or AB ( MIGRAINE* OR CEPHALGI* OR CEPHALALGI* OR “FUNCTIONAL ABDOMINAL PAIN” ) 

S43 DE "Headache" OR DE "Migraine Headache" OR DE "Muscle Contraction Headache" OR DE "Migraine Headache" OR DE "Muscle Contraction Headache" 

S42 S40 and S41 S41 S35 or S36 or S37 or S38 or S39 

S40 TI ( CHRONIC* OR RECURR* OR PERSIST* OR FREQUENT* ) or AB ( CHRONIC* OR RECURR* OR PERSIST* OR FREQUENT* ) 

S39 DE "Myofascial Pain" 

S38 TI "Temporomandibular Joint Dysfunction Syndrome" or AB "Temporomandibular Joint Dysfunction Syndrome" 

S37 TI ( BACKACHE OR “BACK-ACHE” OR BACKACHES OR “BACK-ACHES” ) or AB ( BACKACHE OR “BACK-ACHE” OR BACKACHES OR “BACK-ACHES” ) 

S36 TI ( PAIN* OR ACHE* ) or AB ( PAIN* OR ACHE* ) 

S35DE "Pain" OR DE "Aphagia" OR DE "Back Pain" OR DE "Chronic Pain" OR DE "Headache" OR DE "Myofascial Pain" OR DE "Neuralgia" OR DE "Neuropathic Pain" OR DE "Somatoform Pain Disorder" 

S34 S20 and S29 and S33 S33 S8 or S32 S32 S9 or S10 or S14 or S15 or S16 or S17 or S18 or S19 or S31 S31 TI ( HEADACHE* OR "HEAD ACHE" ) or AB ( HEADACHE* OR "HEAD ACHE" ) S30 S22 and S29 S29 S23 or S24 or S25 or S26 or S27 or S28 S28 DE "Followup Studies" S27 TX incidence or mortality or prognos* or predict* or course* S26 TX cohort N1 stud* S25 TX between N5 group* or TX risk* S24 DE "Cohort Analysis" OR DE "Longitudinal Studies" S23 DE "Risk Assessment" OR DE "Risk Factors" S22 S20 and S21 S21 S8 or S9 or S14 or S15 or S16 or S17 or S18 or S19 

S20 CHILD OR CHILDREN OR ADOLESCENT OR ADOLESCENTS OR ADOLESCENCE OR TEEN* OR YOUTH* OR YOUNG 

S19 TI NEURALGI* or AB NEURALGI* S18 DE "Neuralgia" S17 DE "Dysmenorrhea" 

S16 TI ( Polyarthralgia OR ARTHRALGIA OR FIBROMYALGIA OR DYSMENORRH* ) or AB ( Polyarthralgia OR ARTHRALGIA OR FIBROMYALGIA OR DYSMENORRH* ) 

S15 DE "Fibromyalgia" S14 S2 and S13 S13 S11 or S12 S12 TI "Irritable Bowel Syndrome" or AB "Irritable Bowel Syndrome" S11 DE "Irritable Bowel Syndrome" 

S10TI ( MIGRAINE* OR CEPHALGI* OR CEPHALALGI* OR “FUNCTIONAL ABDOMINAL PAIN” ) or AB ( MIGRAINE* OR CEPHALGI* OR CEPHALALGI* OR “FUNCTIONAL ABDOMINAL PAIN” ) 

S9 DE "Headache" OR DE "Migraine Headache" OR DE "Muscle Contraction Headache" OR DE "Migraine Headache" OR DE "Muscle Contraction Headache" 

S8 S6 and S7 S7 S1 or S2 or S3 or S4 or S5 

S6 TI ( CHRONIC* OR RECURR* OR PERSIST* OR FREQUENT* ) or AB ( CHRONIC* OR RECURR* OR PERSIST* OR FREQUENT* ) 

S5 DE "Myofascial Pain" 

S4 TI "Temporomandibular Joint Dysfunction Syndrome" or AB "Temporomandibular Joint Dysfunction Syndrome" 

S3 TI ( BACKACHE OR “BACK-ACHE” OR BACKACHES OR “BACK-ACHES” ) or AB ( BACKACHE OR “BACK-ACHE” OR BACKACHES OR “BACK-ACHES” ) 

S2 TI ( PAIN* OR ACHE* ) or AB ( PAIN* OR ACHE* ) 

S1DE "Pain" OR DE "Aphagia" OR DE "Back Pain" OR DE "Chronic Pain" OR DE "Headache" OR DE "Myofascial Pain" OR DE "Neuralgia" OR DE "Neuropathic Pain" OR DE "Somatoform Pain Disorder" 

Web of Science

#24 #23 AND #17 #23 #22 OR #21 OR #20 OR #19 OR #18 #22 TS=(FOLLOW SAME UP SAME STUD*) #21 TS=(FOLLOWUP SAME STUD*) #20 TS=(INCIDENCE OR MORTALITY OR PROGNOS* OR PREDICT* OR COURSE*) #19 TS=(BETWEEN SAME GROUP*) #18 TS=(RISk* OR COHORT*) #17 #16 AND #15 #16 #14 OR #13 OR #11 OR #10 OR #9 OR #8 OR #7 #15 TS=(CHILD OR CHILDREN OR ADOLESCENT OR ADOLESCENTS OR ADOLESCENCE OR TEEN* OR YOUTH* OR YOUNG) #14 TS=(Polyarthralgia OR ARTHRALGIA OR FIBROMYALGIA OR DYSMENORRH* OR NEURALGI*) #13 #12 AND #3 #12 TS=(Irritable SAME Bowel SAME Syndrome) #11 TS=(FUNCTIONAL SAME ABDOMINAL SAME PAIN) #10 TS=(MIGRAINE* OR CEPHALGI* OR CEPHALALGI*) #9 TS=(HEAD SAME ACHE*) #8 TS=(HEADACHE*) #7 #6 AND #5 #6 #4 OR #3 OR #2 OR #1 #5 TS=(CHRONIC* OR RECURR* OR PERSIST* OR

FREQUENT* ) #4 ts=(BACKACHE OR BACKACHES) #3 ts=(PAIN* OR ACHE*) #2 TS=(Temporomandibular SAME Joint* ) #1 TS=(BACK SAME ACHE*)

Supplemental Digital Content 2. Operationalization of risk factors assessed for onset of MSK pain

Type of factor Factors identified Definition Measurement Scale Study

Psychosocial factors

Body functions: Functioning at the level of body functions (psychological functioning) a

Prosocial behaviour Prosocial behaviour Score of 3 vs. score of 1 measured on the Strengths and

Difficulties questionnaire Dichotomous [45]

Hyperactivity Hyperactivity Score within 3rd tertile vs. 1st measured on the Strengths and Difficulties questionnaire Dichotomous [45]

Negative emotional states

Depression Score of 11 or greater on the Beck Depression Inventory vs. score less than 11 Dichotomous [8]

Depressed mood Level of depressed mood measured on the Beck Depression Inventory Continuous [27]

Emotional problems Emotional problems score within 3rd tertile vs. 1st on the Strengths and Difficulties questionnaire Dichotomous [27]

Mental distress Averaged score of 1.85 or greater vs. less than 1.85 on the Hopkins Symptoms Checklist Dichotomous [55]

Depressive symptoms

Sad or low mood once per week for the past 3 months vs. less reported low mood Dichotomous [45]

Emotional/ behavioural disorder

Presence of disorder vs. none as measured on validated survey Dichotomous [64]

Emotional status Poorly adjusted vs. well-adjusted/intermediate on Rutter behavioural scale Dichotomous [70]

Depressive feelings Unclear Continuous [79]Self-esteem Self-worth Measured on Global Self-Worth Continuous [27]Self-efficacy Self-efficacy Measured on the Perceived Self-Efficacy scale Continuous [27]Somatosensory amplification

Somatosensory amplification Measured on the somatosensory Amplification Scale Continuous [1]

Pain catastrophizing Pain catastrophizing Measured on the Pain Catastrophizing Scale for

Children Continuous [1]

Activities / Participation: Functioning at the level of the individual or at the level of a person as member of the societya

Functional limitations

Functional limitations Functional limitations for more than 6 months Dichotomous [64]

Dysfunctional stress coping

Dysfunctional stress coping

Score on the German Coping Questionnaire for Children and Adolescents Continuous [1]

Amount of peer problems Peer problems Peer problems score within 3rd tertile vs. 1st on the

Strengths and Difficulties questionnaire Dichotomous [27]

Family functioning Family functioning Score on the General Family Functioning Subscale of

the McMaster Family Assessment Device Dichotomous [27]

School achievement School achievement Average GPA within the 4th quartile vs. within the 1st

quartile Dichotomous [79]

Physical factors Body functions: Functioning at the level of body functions (biological/physiological functions) a

Daytime tiredness

Daytime tiredness

Score between 6-10 vs. score between 0-3 measured on VAS Dichotomous [45]

Daytime tiredness once per week for at least 3 weeks vs. less reported daytime tiredness Dichotomous [58]

Tired without reason Level of tired measured on VAS Continuous [86]

Difficulty falling asleep

Difficulty falling asleep

Difficulty falling asleep at least once per week for the past 3 months vs. less reported sleep difficulty Dichotomous [58]

Quality of falling asleep Level of quality of falling asleep measured on VAS Continuous [86]

Waking up during the night

Waking up during the night

Waking up during the night at least once per week for the past 3 months vs. less reported difficulty Dichotomous [58]

Headache HeadacheGreater than 7 headache days in the past month vs. none Dichotomous [45]Headache once per month or more vs. less than once per month Dichotomous [58]

Sore throat Sore throat Sore throat 7 days or more in the past month vs. none Dichotomous [45]

Abdominal painStomach ache Stomach ache 7 days or more in the past month vs. none Dichotomous [45]

Abdominal pain Abdominal pain once per month or more vs. pain less than once per month Dichotomous [58]

Pain in upper back Pain in upper back Pain in upper back once per month or more vs. pain less

than once per month Dichotomous [58]

Pain in lower back Pain in lower back Pain in lower back once per month or more vs. pain less

than once per month Dichotomous [58]

Pain in upper Pain in upper limb Pain in upper limb once per month or more vs. pain less Dichotomous [58]

limb than once per monthPain in lower limb Pain in lower limb Pain in lower limb once per month or more vs. pain less

than once per month Dichotomous [58]

Chest pain Chest pain Chest pain once per month or more vs. pain less than once per month Dichotomous [58]

Multiple pains Musculoskeletal symptoms

Frequency of musculoskeletal symptoms at least once per week vs. Continuous [84]

Exercise tolerance Exercise tolerance Panting or sweating a lot during exercise vs. a little/ not

at all/ no exercise Dichotomous [79]

Hypermobility Generalized joint hypermobility

Hypermobility score of 6 or more vs. less than 6 on the Beighton test Dichotomous [58,82]

Lumbar flexibility

Lumbar flexibility Measurement on Schober test Continuous [23]Maximum lumbar flexion

Degrees of lumbar flexibility using the flexicurve technique Continuous [51]

Abdominal strength Abdominal strength Measured by abdominal resistance Continuous [23]

Muscle flexibility

Ability to sit and reach Ability to sit and reach for a box, measured in cm Continuous [23]

Activities / Participation: Functioning at the level of the individual or at the level of a person as member of the societya

School bag weight

Weight of school bag

School bag perceived as heavy vs. not perceived as heavy Dichotomous [86]

Relative weight of bag by body weight Continuous [46]

Swimming Swimming and diving

Engagement in swimming and diving vs. no swimming and diving measured by ad-hoc questionnaire Dichotomous [17]

Practicing regular exercise

Sporting activity Greater than 18 sporting activities lasting longer than 20 minutes per week vs. less than 5 sporting activities Dichotomous [46]

Participation in sports Unclear Unclear [51]

Exercise Exercise 5-7 times per week vs. 0-2 times per week Dichotomous [58]Level of physical activity

Very active vs. very passive activity, measured on ad-hoc questionnaire assessing 3 type of physical activity Dichotomous [79]

Regular smoking

Regular alcohol consumption

Smoking

Being a smoker vs. not being a smoker Dichotomous [23,35]Smoked cigarette in past 4 weeks vs. no cigarettes Dichotomous [27]Smoking 5-7 days per week vs. never or occasionally smoking Dichotomous [60]

Alcohol use Consuming more than 1.0 units of alcohol per day vs. less than 0.2 units per day Dichotomous [35]

Time spent on homework

Time spent on homework

Time spent on homework within the 4th quartile vs. within the 1st quartile Dichotomous [79]

Working Time spent working Sum of time spent working over past 6 months Continuous [23]Number of hours worked at part-time job Unclear [46]

Practicing a hobby that loads the upper extremities

Hobbies involving upper extremities

Participation in hobbies involving upper extremities vs. sports involving dynamic loading of all muscle groups vs. sports loading upper extremities vs. other activities

Ordinal [79]

Playing musical instrument Playing a musical instrument vs. no playing instrument Dichotomous [17]

Frequent use of TV, video games

Duration of TV watching Daily duration of TV watching Continuous [86]

Duration of sedentary activities

Greater than 275 minutes of sedentary activity yesterday vs. less than 120 minutes yesterday Dichotomous [45]

Personal factorsa

Poor overall health

Presence of chronic medical condition lasting 6 months or longer vs. no condition Dichotomous [64]

Psychosomatic symptom score on questionnaire Continuous [79]Psychosomatic and physical symptoms score on questionnaire Continuous [84]

Perception of health on VAS Continuous [86]

Fitness Self-assessed good physical condition vs. fairly poor or poor Dichotomous [79]

Body Measurement factors

Body structure: Functioning at the level of body structuresa

Pelvic tilt Unclear Routine medical checkup Unclear [86]

Head tilt Head tiltTilt 18.6 degrees or greater or 6.9 degrees or less all other angles measured through Photographic Posture Analysis Method

Dichotomous [8]

Cervical tilt Cervical tiltTilt of 43.95 degrees or greater or 34.75 degrees or less vs. all other angles measured through Photographic Posture Analysis Method

Dichotomous [8]

Thoracic tilt Thoracic tilt Tilt of 71.1degrees or greater or 63.1 degrees or less vs. Dichotomous [8]

all other angles measured through Photographic Posture Analysis Method

Shoulder protraction Shoulder protraction

Retraction of 141.4 degrees or greater or 117.4 degrees or less vs. all other angles measured through Photographic Posture Analysis Method

Dichotomous [8]

Kyphosis

Extreme cervical and thoracic angles Unclear Dichotomous [8]

Lumbar standing posture

Degrees of lumbar sagittal flexibility measured by the flexicurve technique Continuous [51]

Kyphosis Measured in degrees by physiotherapist Continuous [65]Structure of vertebral column Increase in kyphosis, measured by physiotherapist Continuous [65]

Personal factorsa

Height

Measured in cm Continuous [23,51,69,86]

Height of 1.63 meters or more vs. less than 1.63 meters Dichotomous [8]Height between 166-188 cm vs. between 120-150 cm Dichotomous [46]Height at age 7 greater than 85th percentile vs. less than 15th percentile Dichotomous [70]

Height in the 4th quartile vs. in the 1st Dichotomous [8]

Change in heightChange in height of 5cm over past 6 months vs. change less than 5cm Dichotomous [23]

Measurement of height change, in cm Continuous [65]Sitting height Measured in cm Continuous [65]Change in sitting height Measured in cm Continuous [65]

WeightWeight of 54.2 kg or greater vs. less than 54.2 kg Dichotomous [8]Weight between 60-95 kg vs. between 24-40 kg Dichotomous [46]Measured in kg Continuous [51,86]

Body mass index

Weight in kg/ height in m2 Continuous [24,46,51,69]

BMI of 20.4 kg/ m2 or greater vs. BMI less than 20.4 kg/ m2 Dichotomous [8]

BMI of 24 kg/ m2 or greater vs. less than 24 kg/ m2 Dichotomous [35]Persistence of obese BMI, as measured by Cole’s international criteria Dichotomous [61]

BMI in the 3rd quartile vs. in the 1st Dichotomous [79]BMI greater than the 85th percentile vs. between the 30th

– 70th percentile Dichotomous [70]

Change of BMI Measured in kg/ m2 Continuous [65]

Sociodemographic factors

Personal factorsa

Female sex Female vs. male sex Dichotomous [6,8,23,45,58,61,70,79,86]

Older ageAge, in years Continuous [23,86]Age 14 vs. age 11 Dichotomous [45]Children 11-12 years vs. 9-10 years Dichotomous [58]

Socioeconomic status

Estimated from the Socio economic Index for areas Continuous [27]Deprivation level on Townsend Index Dichotomous [45]Parental education, high school or less vs. college or university degree Dichotomous [64]

Father’s occupation, professional and intermediate vs. manual Dichotomous [70]

Blue collar work Blue collar work vs. not working Dichotomous [23]White collar work White collar work vs. not working Dichotomous [23]Childcare work Childcare work vs. not working Dichotomous [23]

aFactors are grouped according to the ICF-CY domains of functioning and disability: Body Functions; Body Structures; Activities and Participation; Environment; and Personal Factors.

Supplemental Digital Content 3. Operationalization of prognostic factors assessed for persistence of MSK pain

Type of factor Factors identified Definition Measurement Scale Study

Psychosocial factors

Body functions: Functioning at the level of body functions (psychological functions) a

Global psychosocial functions

Psychosocial functioning Score on the Children’s Global Assessment Scale Continuous [25]

Total difficulties High total difficulties measured on the Strengths and Difficulties questionnaire vs. low total difficulties Dichotomous [44]

Negative emotional states

Emotional problems High emotional problems measured on the Strengths and Difficulties questionnaire vs. low problems Dichotomous [44]

Anxiety or depression symptoms

Score on the Emotional Disorder Scale from the Feelings and Behaviour Questionnaire Ordinal [85]

Depressive feelings Depressive feelings experienced once per month or more vs. seldom or never Dichotomous [18]

Prosocial behaviour Prosocial behaviour High prosocial behaviour measured on the Strengths and

Difficulties questionnaire vs. low prosocial behaviour Dichotomous [44]

Hyperactivity Hyperactivity High hyperactivity measured on the Strengths and Difficulties questionnaire vs. low hyperactivity Dichotomous [44]

Self-esteem Low self-esteem Score on the General Self Scale of the Self-Description Questionnaire Ordinal [85]

Activities / Participation: Functioning at the level of the individual or at the level of a person as member of the societya

Functional limitations

Symptoms of disability Experiencing 1-2 symptoms of disability vs. 0 symptoms Dichotomous [18]

Functional limitations

Moderate limitations to functional ability assessed on 9 daily activities vs. low limitations Dichotomous [44]

High limitations to functional ability assessed on 9 daily activities vs. low limitations Dichotomous [44]

Informal relationships with friends

Peer problems High peer relationship problems measured on the Strengths and Difficulties questionnaire vs. low problems Dichotomous [44]

Physical factors Body functions: Functioning at the level of body functions (biological/physiological functions) a

Daytime tiredness Daytime tiredness

Score on Somatic Symptoms questionnaire between 5-10 v. score between 0-4 Dichotomous [44]

Daytime tiredness experienced once per month or more vs. seldom or never Dichotomous [18]

Difficulty falling asleep

Difficulty falling asleep

Difficulty falling asleep experienced once per month or more vs. seldom or never Dichotomous [18]

Waking up at night Waking up at night Waking up during the nights experienced once per month or

more vs. seldom or never Dichotomous [18]

Headache Headache

Headache experienced once per month or more vs. seldom or never Dichotomous [18]

Headache experienced between 1-7 days in the past month vs. no headache Dichotomous [44]

Abdominal pain Abdominal pain

Abdominal pain experienced once per month or more vs. seldom or never Dichotomous [18]

Abdominal pain experienced between 1-7 days in the past month vs. no abdominal pain Dichotomous [44]

Low back pain Low back pain Experiencing low back pain on day of assessment vs. no low back pain Dichotomous [44]

Frequency FrequencyPain experienced more than once per week vs. once per week Dichotomous [19]

Pain experienced several times per week vs. rarely Dichotomous [73]

Frequency of pain locations

Frequency of pain locations

Regional pain, only one pain location vs. combined pain, multiple pain locations Dichotomous [18]

Number of painful sites, ranging from 0-6 Continuous [25]

Widespread painWidespread pain Widespread pain in the past month vs. no widespread pain Dichotomous [44]

Generalized pain Pain affecting 3 or more sites vs. pain affecting fewer than 3 sites Dichotomous [25]

Type of MSK Type of MSK Idiopathic MSK vs benign joint hypermobility Dichotomous [83]

Lifetime duration of pain

Lifetime duration of pain

Years of disease duration prior to admission Continuous [25]Low back pain initiating greater than 12 months prior vs. initiating less than one month prior Dichotomous [44]

# days with pain # days with pain Experiencing greater than 30 days with pain in the previous Dichotomous [36]

year vs. between 1-7 daysDuration of pain episodes

Duration of pain episodes

Typical duration of low back pain is experienced between 7-10 days vs. less than 24 hours Dichotomous [44]

Severity Severity

Pain experienced in the previous week, ranging from 0-10cm on VAS Continuous [25]

Worst pain severity in previous month between 7-10 on 10 point scale vs. worst severity between 0-3 Dichotomous [44]

Lower limb injury Lower limb injury Lower limb injury vs. no lower limb injury Dichotomous [19]Radiating pain in a segment or region

Radiating leg pain Radiating leg pain vs. no radiating leg pain Dichotomous [44]

Oxygen intake Oxygen intake Maximum units of oxygen intake, measured by performance in shuttle run test Continuous [18]

Elevated C-reactive protein Immune response Elevated C-reactive protein greater than 5mg/dl vs. less than

5mg/dl Dichotomous [25]

Clotting functions Clotting functions Elevated platelet count greater than 400 x 103/mm3 vs. less than 400103/mm3 Dichotomous [25]

Hypermobility Hypermobility Score of 6 or greater on Beighton’s method of testing hypermobility vs. score less than 6 Dichotomous [18]

Flexibility Distance between fingertip to floor when bending Continuous [44]

PubertyPubertal stage Presence of secondary signs of pubertal development vs.

pre-pubertal development Dichotomous [83]

Puberty onset 4-point Likert scale ranging from ‘has not started’ to ‘seems completed’ Ordinal [85]

Activities / Participation: Functioning at the level of the individual or at the level of a person as member of the societya

Hospitalization Hospitalization Staying overnight in hospital in past year vs. no overnight stay Dichotomous [85]

Regular smoking Smoking frequency Smoking between 5-7 days per week vs. non-smokers or occasional smokers Dichotomous [60]

Number of cigarettes

Number of cigarettes smoked

Smoking greater than 1-9 cigarettes per day vs. smoking 0 cigarettes Dichotomous [60]

Practicing regular exercise

Exercise Exercising between 5-7 half-hour periods per week vs. no exercise per week Dichotomous [73]

Sports participation Sports participation between 3-7 times per week vs. 0-2 times Dichotomous [59]

Driving to school Travel to school Travelling to school by means other than walking vs. travelling by walking Dichotomous [44]

School absence due to pain

School absence due to pain

School absence due to pain one or more days in previous year vs. no absence due to pain Dichotomous [19]

Personal factorsa

Life events Life events Chronic family difficulties Continuous [25]Number of stressful life events Continuous [85]

Poor overall health

Poor overall health 4-10 Yunis criteria symptoms (pain modulation ) vs. 0-1 Dichotomous [59]Number of injuries requiring medical attention Continuous [85]

Body Measurement factors

Personal factorsa

Being short Being short Shorter than median height (158 cm) vs. taller Dichotomous [44]Weight Weight Weight, in kg Continuous [44]

BMI BMI BMI by kg/ height in m2 Continuous [44,74,83]

Environmental factors

Environment factorsa

Family history of pain

Family history of disease

Presence of family history of disease related to pain vs. no family history Dichotomous [25]

Sociodemographic factors

Personal factorsa

Female sexOlder ageHigh socio-economic status

Female sex

Female vs. male sex Dichotomous [6,18,25,73,85]

Older ageAge between 11-13 years vs. age between 9-10 years Dichotomous [18]Age, between 12-15 years Continuous [73]Age, in years Continuous [83]

High socio-economic status Father’s years of education Continuous [25]

aFactors are grouped according to the ICF-CY domains of functioning and disability: Body Functions; Body Structures; Activities and Participation; Environment; and Personal Factors.

Supplemental Digital Content 4. Operationalization of outcome variables

Study Outcome Definition MeasurementChronic/recurrent pain

Barke et al. [1] OnsetSelf-report of recurrent back pain at least ‘sometimes, often, or always’ in the previous 6 months vs. seldom or never

Ad-hoc question assessing back pain frequency on a 5-point Likert scale

Brattberg [6] Onset Self-report of having back pain ‘often’ for at least one month

Ad-hoc question asking frequency of back painPersistence

El-Metwally et al. [18] Persistence Self-report of musculoskeletal pain at least once per week in the previous 3 months

Structured pain questionnaire, classified according to body area on diagram and frequency

El-Metwally et al. [19] Persistence Self-report of lower limb pain at least once per week in the previous 3 months

El-Metwally et al. [21] OnsetSelf-report of non-traumatic or traumatic musculoskeletal pain at least once per week in the previous 3 months

Mikkelsson et al. [59] Persistence Self-report of musculoskeletal pain occurring for at least one week in the previous 3 months

Mikkelsson et al. [58] Onset Self-report of widespread pain occurring for at least 3 months

Stahl et al. [84] Onset Self-report of neck pain at least once per week for at least 3 month

Feldman et al. [22] Onset Self-report of low back pain at least once per week in previous 6 months

Self-administered questionnaire addressing musculoskeletal health

Feldman et al. [23] Onset

Feldman et al. [17] Onset Self-report of neck or upper limb pain at least once per week in the previous 6 months

Feldman et al. [24] Onset Self-report of musculoskeletal pain at least once per week in the previous 6 months

Shrier et al. [78] Onset Self-report of lower limb, hip, knee, leg, foot or ankle pain at least once per week in previous 6 months

Flato et al. [25] PersistenceSelf-report of persisting chronic idiopathic musculoskeletal pain lasting for at least 3 months at each time point of assessment

Clinical examination by pediatric rheumatologist

Hestbaek et al. [36] Persistence Self-report of low back pain for 30 days or more in the previous year

Nordic Back Pain questionnaire asking number of days with back pain in previous yearHestbaek et al. [35] Onset

Lien et al. [56] Onset Self-report of being troubled with neck, shoulder, or back pain in the course of the last 12 months

Ad-hoc question asking trouble with pain in the previous 12 months

Rathleff et al. [73] Persistence Self-report of knee pain at least monthly in the previous year

Questionnaire and pain charts measuring musculoskeletal pain

Siivola et al. [79] Onset Self-report of neck or shoulder pain, occasional or weekly for the previous six months

Questionnaire modified from the Nordic Musculoskeletal questionnaire

Sohrbeck-Nohr et al. [82] Onset Self-report of joint pain in more than four joints for

more than three months Brighton criteria for arthralgia

Sperotto et al. [83] PersistenceSelf-report of chronic musculoskeletal pain heavily interfering with daily activities for at least three months

Clinical assessment interview with pediatrician

Stanford et al. [85] Persistence Self-report of recurrent backache about once a month or more in the previous six months

Questionnaire derived from the World Health Organization’s survey: Health behaviours in school-age children

Mixed (acute/chronic/recurrent)

Brink et al. [9] OnsetSelf-report of upper quadrant musculoskeletal pain in the preceding month (at either 3, or 6-month follow-up)

Unclear

Gill et al. [27] Onset Self-report of neck, shoulder, low back, or mid back pain in the previous month

Ad-hoc question asking if neck/ shoulder/ low back/ mid back has been painful at any time in the previous month

Jones et al. [46] Persistence

Self-report of widespread pain lasting for one day or longer in the previous month

Ad-hoc questionnaire

Jones and MacFarlane [44] Onset

Ad-hoc question asking frequency of low back pain, classified according to body area on diagram

Jones et al. [45] OnsetAd-hoc question asking frequency of widespread pain, classified according to body area on diagram

Kujala et al. [51] Onset Self-report of low back pain interfering with activities for at least one week

Ad hoc questionnaire asking occurrence of low back pain

Lake et al. [52] Onset Self-report of often experiencing low back pain, for Semi-structured interview based on the

more than one day in the previous yearMalaise Inventory checklist for back pain, asking occurrence of low back pain, classified according to body area on diagram

Power et al. [70] Onset

Mikkonen et al. [60] OnsetSelf-report of low back pain in the previous 6 months

Ad-hoc question asking occurrence of low back pain, classified according to body area on diagram

PersistenceMikkonen et al. [61] Onset

Mustard et al [64] Onset Self-report of low back pain lasting more than 1 day in the previous 12 months

Questionnaire items asking occurrence of low back pain in previous 12 months

Nissinen et al. [65] Onset Self-report of low back pain in the previous yearStandardized pain questionnaire asking occurrence and frequency of low back pain in the previous year

Poussa et al. [69] Onset Self-report of low back pain eight or more days in the previous year

Ad-hoc structured questionnaire asking frequency of back pain in the previous year, classified according to body area on diagram

Szpalski et al. [86] Onset Self-report of at least one episode of low back pain in the previous two years

Clinical examination and ad-hoc questionnaire asking about pain

Supplemental Digital Content 5. GRADE assessment of potential risk factors for onset of MSK pain

Univariate Multivariate GRADE*Type of factor

Factors identifiedb

N#

cohorts

+ 0 - + 0 - Phase Study limit.

Inconsis. Indirect Imprec. Pub

biasLgES

Dose Overall quality

Body functions: Functioning at the level of body functions (psychological functions)a

Psychosocial factors

Prosocial behaviour 1081 1 0 0 1 1 +Hyperactivity 1081 1 0 1 0 1 +

Negative emotional states

11316 8 2 5 1 2 1 0 1 & 2 +++10922 7 OR 1.54 (1.06-2.24) 1 & 2 ++++

Self-esteem 721 1 0 1 0 2 +Self-efficacy 721 1 0 1 0 2 +

Pain catastrophizing 1665 1 0 2 0 2 +Somatosensory amplification 1665 1 2 0 0 2 +

Activities / Participation: Functioning at the level of the individual or at the level of a person as member of the societya

Functional limitations 1039 1 0 1 0 0 1 0 1 +Dysfunctional stress

coping 1665 1 0 1 1 2 +

Amount of peer problems 1081 1 0 1 0 1 +

Family functioning 721 1 0 0 1 2 +School achievement 57 1 0 1 0 1 +

Physical factors Body functions: Functioning at the level of body functions (biological/physiological functions)a

Daytime tiredness 2650 3 1 2 0 0 1 0 1 +Difficulty falling

asleep 1569 2 1 1 0 0 1 0 1 +

Waking up during nights 1282 1 1 0 0 0 1 0 1 +

Headaches 2363 2 2 0 0 0 1 0 1 +Sore throat 1081 1 0 1 0 1 +Neck pain 1282 1 1 0 0 1 0 0 1 +

Abdominal pain 2363 2 1 1 0 0 1 0 1 +Pain of spinous

processes 287 1 1 0 0 1 +

Upper back pain 1282 1 0 1 0 0 1 0 1 +Lower back pain 1282 1 0 1 0 0 1 0 1 +Upper limb pain 1282 1 0 1 0 0 1 0 1 +Lower limb pain 1282 1 0 1 0 0 1 0 1 +

Chest pain 1282 1 0 1 0 1 +Multiple pains 1268 1 1 1 0 1 +

Exercise tolerance 66 1 0 1 0 1 +Hypermobility 1582 2 0 2 0 0 1 0 1&2 +++

Lumbar flexibility 600 2 0 2 0 0 2 0 1&2 +Abdominal strength 502 1 0 1 0 1 +Muscle flexibility 600 2 0 1 0 0 1 0 1 +

Decrease in muscle flexibility

502 1 1 0 0 1 +

Activities / Participation: Functioning at the level of the individual or at the level of a person as member of the societya

School bag weight 1220 2 0 2 0 1 Unclear Unclear ++Swimming 502 1 0 1 0 1 +

Practicing regular exercise 1836 4 0 3 0 2 1 0 1 & 2 ++

Regular smoking 7117 4 1 2 0 2 2 0 1 & 2 +++Regular alcohol

consumption 3907 1 0 1 0 1 +

Time on homework 75 1 0 1 0 1 +Working 1435 2 0 1 0 1 0 0 1 +

Number hours working 1435 2 1 1 0 1 +Practicing a hobby that

statically loads the upper extremities

896 2 0 1 0 0 1 0 1 +

Frequent use of TV, video games 1461 3 0 3 0 1 & 2 ++

Personal factorsa

Poor overall health 4043 4 4 1 0 1 1 0 1 +Physical fitness 55 1 0 1 0 1 +

Body Measurement factors

Body structure: Functioning at the level of body structuresa

Pelvic tilt 1146 2 0 3 0 1 +Head tilt 93 1 0 1 0 2 +

Cervical tilt 93 1 1 0 0 2 +Thoracic tilt 93 1 0 1 0 2 +

Shoulder protraction 93 1 0 1 0 2 +Increase in kyphosis 859 1 0 1 0 1 +

Kyphosis 1050 3 1 2 0 0 1 0 1 & 2 +Personal factorsa

Taller Height 3039 8 1 6 0 0 3 0 1 & 2 +++1820 5 OR 1.42 (1.13-1.78) +++

Change in height 1361 2 0 2 0 1 0 0 1 +Sitting height 859 1 1 0 0 1 +

Change in sitting height 859 1 0 2 0 1 +

Heavier weight 814 4 1 4 0 1 2 0 1 & 2 ++814 4 OR 1.22 (0.81-1.85) ++

High BMI 10504 9 0 7 0 1 5 0 1 & 2 +++2824 4 OR 1.10 (0.80-1.52) 1 & 2 +++

Change of BMI 859 1 0 1 0 1 +Environmental factors

Environment factorsa

Parental chronic pain 37 1 0 1 0 1 +Sociodemographic factors

Personal factorsa

Female sex 11368 9 2 5 1 1 1 1 1 & 2 +

10579 7 OR 1.28 (0.86-1.91) 1 & 2 ++Older age 3152 4 1 2 0 0 2 0 1 +

Low socio-economic status

5403 4 2 2 0 1 0 0 1&2 ++++5403 4 OR 1.42 (0.98-2.05) 1&2 ++++

Blue collar work vs not working 502 1 0 1 0 1 +

White collar work vs not working 502 1 1 0 0 1 +

Childcare work vs not working 502 1 0 1 0 1 +

ICF-CY = International Classification of Functioning, Disability and Health for Children and Youth. aFactors are grouped according to the ICF-CY domains of functioning and disability: Body Functions; Body Structures; Activities and Participation; Environment; and Personal Factors. bEach factors maps onto the most specific subcategory within the specified ICF-CY domain. Supplemental Digital Content 2 provides an operationalization of each risk factor listed in this table. Univariate and multivariate results: += Number of cohorts (or subcohorts when analysis is stratified by sex) that find a positive association between factor and outcome; 0= Number of cohorts (or subcohorts when analysis is stratified by sex) that find no association between factor and outcome; -= Number of cohorts (or subcohorts when analysis is stratified by sex) that find a negative association between factor and outcome. GRADE factors: Phase=Phase of investigation, Study limit. = Study limitations, Inconsis. = Inconsistency, Indirect = Indirectness, Imprec. = Imprecision, Pub. bias = Publication bias, Mod-lg ES = Moderate – large effect size. = no serious limitations, = serious limitations, = very serious limitations, unclear = unable to rate item based on available information. Overall quality of evidence: + = very low, ++ = low, +++ = moderate, ++++ = high.

Supplemental Digital Content 6. Forest plots of selected potential risk factors for onset of MSK pain

6a. Effects of female sex by univariate analyses

Brattberg [6]Brink et al. [8]Jones et al. [45]Mikkelson et al. [58]Mikkonen et al. [61]Power et al. [70]Siivola et al. [79]Szpalski et al. [86]

6c. Effects of low SES by univariate analyses

Gill et al. [27]Jones et al. [45]Mustard et al. [64]Power et al. [70]

6d. Effects of low SES by multivariate analyses

Mustard et al. [64]

6e. Effects of practicing regular exercise by univariate analyses

Jones et al. [46]Siivola et al. [79]Mikkelsson et al. [58]

Jones et al. [46]Kujala et al. [51]Mikkelsson et al. [58]

6g. Effects of regular smoking by univariate analyses

Gill et al. [27]Mikkonen et al. [60] MMikkonen et al. [60] F

6h. Effects of regular smoking by multivariate analyses

Feldman et al. [23]Hestbaek et al. [35]Mikkonen et al. [60] MMikkonen et al. [60] F

Feldman et al. [23]Mikkelson et al. [58]Power et al. [59]

6b. Effects of female sex by multivariate analyses

6f. Effects of practicing regular exercise by multivariate analyses

Brink et al. [8]Kujala et al. [51]MKujala et al. [51] FMikkonen et al. [61] FMikkonen et al. [61] MPower et al. [70]Siivola et al. [79]

6i. Effects of BMI by univariate analyses

Feldman et al. [17]Hestbaek et al. [35]Jones et al. [46]Mikkonen et al. [61] FMikkonen et al. [61] MPoussa et al. [69]

6j. Effects of BMI by multivariate analyses

Brink et al. [8]Jones et al. [46]Kujala et al. [51] MKujala et al. [51] FPower et al. [70]Siivola et al. [79]Szpalski et al. [86]

6k. Effect of height by univariate analyses

Feldman et al. [23]Jones et al. [46]Poussa et al. [69]

6l. Effects of height by multivariate analyses

6m. Effects of weight by univariate analyses

Brink et al. [8]Jones et al. [46]Kujala et al. [51] MKujala et al. [51] FSzpalski et al. [86]

6n. Effects of weight by multivariate analyses

Jones et al. [46]Kujala el al. [51] FSzpalski el al. [86]

Favorable prognosis Worse prognosis

Mikkelsson et al. [58]

Mustard et al. [64]

Power et al. [70]

6p. Effects of negative emotional symptoms by multivariate analyses

Favorable prognosis Worse prognosis

Brink et al. [8]Gill et al. [27]Jones et al. [45]Lien et al. [56]Mikkelsson et al. [58]Mustard et al. [64]Power et al. [70]Siivola et al. [79]

6o. Effects of negative emotional symptoms by univariate analyses

Supplemental Digital Content 7. GRADE assessment of prognostic factors for persistence of MSK painUnivariate Multivariate GRADE*

Type of factor

Factors identifiedb N#

cohorts

+ 0 - + 0 - Phase

Study

limit.

Inconsis.

Indirect

Imprec.

Pub

bias

LgES

Dose effec

tOverall quality

Body functions: Functioning at the level of psychosocial body functionsa

Psychosocial factors

Good psychosocial functioning

215 2 0 2 0 1 +

Negative emotional states

1996 3 2 1 0 0 2 0 1 ++

Prosocial behaviour 178 1 0 1 0 1 +

Hyperactivity 178 1 0 1 0 1 +

Self-esteem 1415 1 0 1 0 1 Unclea

r +

Activities / Participation: Psychological/ social functioning at the individual level as a member of societya

Moderate functional limitations

581 2 0 2 0 0 1 0 1 ++

High functional limitations 645 3 3 0 0 1 1 0 1 +

High levels of peer problems 178 1 1 0 0 1 0 0 1 +

Physical factors Body functions: Functioning at the level of biological/physiological body functionsa

Daytime tiredness 581 2 0 2 0 0 1 0 1 +Difficulty falling

asleep 403 1 0 1 0 0 1 0 1 +

Waking up during nights 403 1 0 1 0 0 1 0 1 +

Headaches 581 2 1 1 0 1 0 0 1 +Abdominal pain 581 2 1 1 0 0 1 0 1 +

LBP 178 1 0 1 0 1 +Frequency 392 2 0 2 0 0 2 0 1 +

Number of pain sites 440 2 2 0 0 1 1 0 1 +

Widespread pain 215 2 1 1 0 1 1 0 1 +Type of MSK

(idiopathic MSK vs benign joint hypermobility)

70 1 1 0 0 1 +

Lifetime duration of pain 215 2 2 0 0 1 1 0 1 +

# days with pain 4642 1 1 0 0 1 +

Duration of pain episodes

178 1 1 0 0 1 +

Univariate Multivariate GRADE*Type of factor

Factors identifiedb N#

cohorts

+ 0 - + 0 - Phase

Study

limit.

Inconsis.

Indirect

Imprec.

Pub

bias

LgES

Dose effec

tOverall quality

Body functions: Functioning at the level of psychosocial body functionsa

Severity 215 2 1 1 0 0 1 0 1 +Pain due to injury 228 1 0 0 1 0 0 1 1 +Radiating leg pain 178 1 1 0 0 1 0 0 1 +

Depth of respiration 403 1 0 1 0 0 1 0 1 +

Elevated C-reactive protein 37 1 0 1 0 1 +

Clotting functions 37 1 0 1 0 1 +Hypermobility 581 2 1 1 0 1 0 0 1 ++

Puberty 1485 2 1 1 0 1 +

Activities / Participation: Physical or active individual functioning, or as a member of societya

Hospitalization 1415 1 0 1 0 1 Unclea

r +

Regular smoking 1987 1 1 1 0 1 1 0 2 +

Number of cigarettes

1987 1 0 2 0 1 1 0 2 +

Practicing regular exercise 679 2 0 1 0 2 0 0 1 +

Driving to school 178 1 0 1 0 1 +School absence

due to pain 403 1 0 1 0 0 1 0 1 +

Personal factors: Physical functioning of personal factorsa

Life events 1452 2 1 1 0 0 1 0 1 +

Poor overall health

1743 2 0 1 0 0 1 0 1 +

Body Measurement factors

Personal factors: Physical functioning of personal factorsa

Taller height 178 1 0 0 1 1 0 0 1 +HeavierWeight 178 1 0 1 0 1 +

High BMI 412 3 0 3 0 0 1 0 1 +

Environmental factors

Environment factors: Functioning related to environmental influencesa

Family history of pain 37 1 0 1 0 1 +

Sociodemographic factors

Personal factorsa

Female sex2616

5 3 2 0 2 1 0 1 +

Older age 664 3 1 2 0 2 0 0 1 +Low socio-

economic status 37 1 1 0 0 0 1 0 1 +

ICF-CY = International Classification of Functioning, Disability and Health for Children and Youth. aFactors are grouped according to the ICF-CY domains of functioning and disability: Body Functions; Body Structures; Activities and Participation; Environment; and Personal Factors. bEach factor maps onto the most specific subcategory within the specified ICF-CY domain. Supplemental Digital Content 3 provides an operationalization of each prognostic factor listed in this table. Univariate and multivariate results: += Number of cohorts (or subcohorts when analysis is stratified by sex) that find a positive association between factor and outcome; 0= Number of cohorts (or subcohorts when analysis is stratified by sex) that find no association between factor and outcome; -= Number of cohorts (or subcohorts when analysis is stratified by sex) that find a negative association between factor and outcome. GRADE factors: None of the factors had an associated Dose Effect, this GRADE item is therefore not included in the table. Phase=Phase of investigation, Study limit. = Study limitations, Inconsis. = Inconsistency, Indirect = Indirectness, Imprec. = Imprecision, Pub. bias = Publication bias, Mod-lg ES = Moderate – large effect size. = no serious limitations, = serious limitations, = very serious limitations, unclear = unable to rate item based on available information. Overall quality of evidence: + = very low, ++ = low, +++ = moderate, ++++ = high.

Supplemental Digital Content 8. Forest plots of selected prognostic factors for persistence of MSK pain

8a. Effects of female sex by univariate analyses

Brattberg et al. [6]El-Metwally et al. [18]Flato et al. [25]Rathleff et al. [73]Stanford et al. [85]

8b. Effects of female sex by multivariate analyses

El-Metwally et al. [18]

Rathleff et al. [73]

Standford et al. [85]

El-Metwally et al. [18]Jones & MacFarlane [44]Stanford et al. [85]

El-Metwally et al. [18]

Stanford et al. [85]

8c. Effects of negative emotional symptoms by univariate analyses 8d. Effects of negative emotional symptoms by mutivariate analyses

Favorable prognosis Worse prognosis

Favorable prognosis Worse prognosis