moderate to severe pain (44%) than those on medical units (13%). Other studies described ev en higher prevalence rates of moderate to severe pain intensity; Taylor et al. (2008) state d that approximately 50% of hospitalized children from one tertiary level academic pae- dia tric hospital reported moderate to severe pain during their stay with 23% reporting persist ent pain. Several studies indicate that child risk factors (e.g. age) and hos- pital service (e.g. su rgical) are associated with the highest levels of moderate to severe pain (e.g. Groenewald et al., 2012; Stevens et al., 2011). Chronic pain Neonates and infants As with acute pain, health professionals responsible for the care provision of infants and parents may harbor misconceptions or lack understanding o f prolonged, persistent, or chronic pain in infancy. In a recent study by Pillai Riddell et al. (2009), two types of prolonged pain were described by the health professionals for hos pitalized infants including \200\230chronically pained \200\231 (a pain state that involve d prolonged exposure of the infant to repetitive pain- ful procedures, which was characteri zed by overlap with recovery from a previous painful procedure) and \200\230chronic pain \200\231 (related to the aft ermath of acute pain that is prolonged and has not resolved du e to unknown cause) in infants. Examples of infants exhibiting chronic pain include: (1) a subgroup of postsurgical gastrointes- tinal patients ( \200\230short-gut babies \200\231) w ho continue to be distressed weeks aft er the completion of painful surgeries and reduction s, (2) infants with chronic intestinal problems who suff er repetitive bouts of abdominal d iscomfort due to an inability to tolerate feeds and a distended abdomen, (3) infants who su ff er from osteogen- esis imperfecta, (4) infants who have sickle cell disease, (5) infants who have invasive malignant tumors, and (6) extremely low birth weight babies seen months/ years later in follow-up clinics who would not weight bear or walk on their scarred heels ( i.e. from repetitive heel lancing). In Johnston et al. \200\231s 2011 study, the mean of 5.8 (SD 15, range 0 \200\22389) tissue -damaging procedures per infant appears to be a signif- icant improvement. In 1996, no infa nts received pharmacological interventions for heel lancing \200\224the most common of the tissue- damaging procedures \200\224whereas in 2011, of the 46% of infants who were exposed to tissue-damaging procedures, 14.5% were admin- istered opioids and 14.3% received sweet- tasting solutions such as sucrose or glucose. Johnston et al. concluded that although the p revalence of painful procedures was lower in the more recent sur- vey, pain management of p rocedures had generally not improved signifi cantly. In other countries, hospitalized infants were reported to experi- ence an average of 12 tis sue-damaging procedures per day (Carbajal et al., 2008). Carbajal and colleagues reported t hat, of 42 413 painful procedures performed on 430 infants, 79.2% of patients received no p reprocedural analgesia, 2.1% received pharmacological interven- tions, while 18.2% painful procedures were managed using non- pharmacological strategies. Th ese data continue to support that there are a signifi cant number of painful procedures performed on hospitalized infants and a gross undertreatment of procedural pain in infants. Anecdotal evidence from professional and parental caregivers suggests that there are signif i cant numbers of medically comprised infants that are potentially experiencing chronic pai n; however, there are no precise estimates of prevalence. Th ese infants and young children may be even more vulnerable to the consequences of chronic pain and suff ering as manageme nt strategies that are geared for the acute pain context may be ineff ective. Th e longer u ntreated chronic pain continues in infancy, the more likely that maladaptive responses will develop later in life (Buskila et al., 2003; Hamilton and Zeltzer, 1994). Potential respon ses could include central nerv- ous system sensitization, increased functional disability ( Campo et al., 2001; Kashikar-Zuck et al., 2001), dysfunctional cognitive or emotional proce sses, (Eccleston and Crombez, 1999; Taddio, 1999; Taddio et al., 2002), and disrupted famil y functioning. Children and adolescents Several surveys have also been conducted to evaluate the preva- le nce of acute pain in hospitalized children and adolescents. In a recent audit of the epidem iology of procedural pain and pain management in 32 hospital units in eight pediatric hospi tals in Canada, 2987 of 3822 children in the study had undergone at least one painful proce dure in the preceding 24 hours with a mean of 6.3 painful procedures per child (Stevens et al., 2011). Of those who had a painful procedure, 78.1% had a pain management interven- tio n recorded; however, only 28.3% had one or more pain manage- ment interventions administere d and documented specifi cally for the painful procedure (Stevens et al., 2011). Other researchers have focused specifi cally on acute pain inten- sity that is moderate to severe (e.g. >3 or 4 on a 10-point scale). Generally, prevalence rates from these studies a re consistent and high; for example, Ellis et al. (2002) and Cummings et al. (1996) in cros s-sectional studies reported a prevalence rate of 20 \200\22321% of clinically signifi cant pain in hospitalized children in Canada. More recently, Groenewald et al. (2012) reported a prevalence rate of 27% of moderate to severe pain in hospitalized children in the USA. Ad olescents and infants exhibited higher prevalence rates (38% and 32% respectively) than oth er children (17%). In addition, those hospitalized on surgical units demonstrated much high er rates of Children and adolescents Chronic pain has serious developmental and functional implica- tio ns for children and adolescents (King et al., 2011). Chronic pain is common within chronic disease states (e.g. juvenile idiopathic arthritis (JIA), cancer) as well as outside diseas e states. As chronic pain may be associated both with children who are hospitalized, as wel l as those in the community, these two areas will be discussed together in this section, al though chronic pain may also occur in children and adolescents cared for at home or in the community. SECTION 1 introduction 14 Injection pain Needle procedures, including injections, venous access proce- dures, heel st icks, and fi nger lances, are likely to be the most preva- lent causes of iatrogenic pain. A child \200\231s interactions with medical providers are oft en colored by the child \200 \231s fear that s/he will get a shot or a poke. In the USA, healthy children undergo over t hree dozen separate vaccine injections by the time they reach adulthood (<http://www.immuni ze.org/catg.d/p4050.pdf>). A recent study demonstrated that approximately two-thirds of chi ldren have a fear of needles (Taddio et al., 2012). Th is problem persists into adult- hood as approximately 25% of adults are afraid of needles (Taddio et al., 2012) and 10% meet th e criteria for needle phobia (Hamilton 1995). For further discussion of pain associated wit h needle proce- dures see Taddio (Chapter 19, this volume). Th e fi rst comprehensive review on the epidemiology of pain was published by Goodman and M cGrath over two decades ago (Goodman and McGrath, 1991). Prevalence rates, time periods, me asures utilized, and approaches to measurement are variable: \227\206 Perquin et al. (2000), in school and population studies, evaluated 6000 Dutch chi ldren (aged 0 \200\22318 years) and found that 54% had experienced pain in the previous 3 m onths and a fourth had pain which lasted greater than 3 months with about 8% suff ering fro m severe chronic pain. Chronic pain increased with age and was more common in girls. \227\206 Abu-Saad (2010) noted that chronic pain is more likely in girls than boys and increases with advancing age. \227\206 In a Greek study of over 8000 7-year-olds, recurrent complaints of pain (headache , abdominal pain, or limb pain which occurred at least once a week) occurred in 7.2% of the sample (8.8% of girls, 5.7% of boys; p <0.001) (Bakoula et al., 2006). Dental/oral pain Oral and dental pain is a frequent experience in children. Lifetime preval ence of oral pain in 5-year-olds is 25% (Moura-Leite et al., 2008) and in 8- to 10-year-old s is reported in 48% to 88% (Ratnayake and Ekanayake, 2005) with ranges for prevalence in t he preceding 2 months of 24% to 70%. Up to 40% to 59% of children in prevalence studies rep ort having had severe dental pain in the past. Pain impacted the child \200\231s ability to eat, sleep, play, and brush their teeth. Not surprisingly, dental caries are responsible f or the major- ity of oral pain in children (Slade, 2001). Prevalence of oral pain is consis tently higher in lower SES groups (Slade, 2001). \227\206 In a Spanish point prevalence study of 561 8- to 16-year- olds, chronic pain (pai n lasting more than 3 months experi- enced continuously or at least once or twice each mont h) was reported by 37% of the sample although in only 5.1% of the sample was the pain probl em moderate or severe (Huguet and Miro, 2008). \227\206 In a national survey of children in Canada that included 2488 10- to 11-year-olds , up to fi ve times, every 2 years, across 12 to 19 years of age, weekly or more frequent i ncident rates ranged from 26.1% to 31.8% for headache, 13.5% to 22.2% for stomach ache, and 17.5% to 25.8% for backache (Stanford et al., 2008). Growing pains Th e prevalence of growing pains varies widely between 2.6% and 49.4%. Th is disparity is likely to be because of the varying ages and defi nitions for this condition u sed in these studies. Recent studies using more rigorous methodology, larger sample size (5 32 and 596 children), and standard criteria which include only patients with pain that is i ntermittent, bilateral, not involving joints, occurring in the late aft ernoon or evening, with normal physical exam/and labo- ratory studies (Petersen et al., 2003) have found the i ncidence to be 24.5% and 36.9% respectively (Evans and Scutter, 2004; Kaspiris and Zafi rop oulou, 2009). \227\206 Within the community population, in a Canadian study of approximately 500 13-year -olds, 96% experienced acute pain over the previous month. Th e most common acute pains wer e headache (78%), sore muscles (73%), and toothache (45%) (Van Dijk et al., 2006). \227\206 Dangel (2005) reported that approximately 5% of school-age children experience re current abdominal pain (RAP), 5% to 10% experience chronic headaches, and 15% experience mu sculoskel- etal pains with many receiving inadequate treatment. King et al. (2011) used a comprehensive and rigorous approach to systematically review all of the existing literature, which included 41 studies. Th e prevalence of headache ranged f rom 8% to 83%; abdominal pain: 4% to 53%; back pain: 14% to 24%; musculoskel- etal pain: 4% to 40%; multiple pains: 4% to 49%; and other pains: 5% to 88%. Prevalence of chronic pain was higher in girls and increased with age for most pain types. Lower socioeconomic sta- tu s (SES) was associated with higher pain prevalence, especially for headache. Musculoskeletal pain Musculoskeletal pain is commonly reported by children of all ages. Stu dies vary as to the sites of pain evaluated (i.e. as a subset of all pain, all musculoskele tal pain, limb pain, or specifi c joint pain) as well as the reporting period (i.e. point p revalence, weekly, monthly, or more than monthly) and stratifi cation by duration of involv e- ment, which makes it diffi cult to compare fi ndings. Musculoskeletal pain once a week o ccurs in 32%, and once a month in 38.9% of 9- to 11-year-old Finnish children (Mikkelson et al., 1997) but once a week in 8.5% of Swedish 9- to 15-year-olds (Brun Sundblad et al., 20 06), 40% of Brazilian children aged 10-to-18-years within the last 6 months (Zapata at al., 2006), and 45.1% of Italians aged 12 to 16 years had musculoskeletal pain with in the last 12 months (34.4% of who had pain which lasted longer than 3 months) (Masiero et al., 2010) . Six per cent of 1000 consecutive visits to an urban pediatric clinic in the USA were for musculoskeletal pain (de Inocencio, 1998). Th e most common sites of pain include the knee, lower extremities, neck, and spine (de Inocencio, 1998; Masiero et al., 2010; Mikkelsson e t al., 1997). Most studies found Acute and recurrent pain in community health care settings In addition to hospitalized chil dren with a broad array of illnesses, children across the health-illness spectrum also expe rience a variety of acute and chronic pains. Although there is some overlap of acute, recur rent, and chronic pain, these entities will be loosely divided into pain of a more acute na ture and those of a more chronic or persistent nature. Disease-related chronic pain will be discussed separately. CHAPTER 2 prevalence and distribution of pain in children 15 that musculoskeletal pain prevalence increases with age and is more common in girls (King e t al., 2011). Widespread musculoskeletal pain and lower limb pain both persist at a rate of about 30% of the initial population at 1- and 4-year follow-up (El-Metwally et al., 2005; Mikkelsson et al., 2008). For further discussion on infl am- matory arthritis and arthropat hies, see Chira and Schanberg (Chapter 22, this volume) and for non-infl ammatory musculosk el- etal pain, see Clinch (Chapter 24, this volume). In younger children, Kroner-Herwig et al. \200\231s (2007) study of German children aged 7 to 14, showed that headache prevalence in the last 6 months increased from 38.6% in 7- to 8 -year-olds to 63.4% in 13- to 14-year-olds. Th e prevalence of weekly headache increased fr om 2.6% to 9.6%, while weekly prevalence was 23% in Swedish children (Petersen et al., 2003 ). Aromaa et al. (1998) found that 21.7% of 6-year-old Finnish children had a headache whic h impacted their daily activities within their lifetime. Some studies diff erentiate the prevalence of migraine head- ache within larger headache sa mples using criteria defi ned by the International Headache Society by questionnaire or dir ect inter- view (Headache Classifi cation Subcommittee of the International Headache Societ y, 2004). In Bille \200\231s prevalence study of 9000 Swedish children, 1.4% had migraine a t 7 years of age increasing to 5.3% at 15 years of age (Bille, 1962). In a long-term follow -up of 73 of the children with migraine, 23% were migraine free by 25 years of age and 47% were migraine free by age 50 (Bille, 1997). Migraine prevalence was 9.9% in a cohort of Bra zilian children aged 10-18 years (Barea et al., 1996), 10.4% in Turkish children aged 8-16 years (Bugdayci et al., 2005), and 10.6% in British chil- dren aged 5 to 15 years (Abu-Aref eh and Russell, 1994). For more on headache see Hershey (Chapter 31, this volume). Abdominal pain Epidemiological studies of abdominal pain in youth vary by how abdominal pai n, or more typically RAP, is defi ned. Some research- ers use the defi nition by Apley and Naish (1958) of three episodes of abdominal pain over the previous 3 months that limit func tion; however, this is not universal. With the updating of the Rome crite- ria, diff erenti ation of functional abdominal pain syndromes further into functional dyspepsia, irritable b owel syndrome, functional abdominal pain syndrome, and abdominal migraine further clouds th is picture (Drossman, 2006). In a USA study of 507 adolescents, 73% to 78% experienced abdominal pain in the past year, while it occurred weekly in 13% to 24% and impacted function in 17% to 24% of those surveye d (Hyams et al., 1996). Another US study of adolescent girls found a similar weekly prevale nce with 20.7% reporting weekly stomach aches (Ghandour et al., 2004), while in a Canadian adolescent lon- gitudinal sample the prevalence of weekly abdominal pain ranged from 13.5% to 22.2% (Stanford et al., 2008). In Iceland, over 2000 11- to 12- and 15- to 16-year-old c hildren were surveyed. It was found that 18.4% of the sample had at least weekly abdominal pain, and there was a higher prevalence of pain in the younger group and in girls (Kristj nsd ttir, 1996). An Irish study evaluating epigastric pain symptoms in 1133 adolescent s found 6% experienced epigas- tric pain at least once a week (Murray et al., 2007). In a M alaysian sample of 11- to 16-year-olds using Apley \200\231s criteria, the prevalence of pa in was 10.2% (Boey et al., 2000). Pain and obesity Obesity is increasingly prevalent in children and adolescents though few s tudies have addressed pain in this population. Almost two-thirds of 270 overweight and obes e children reported pain in a 1-month period (Lim et al., 2012). Obesity was a risk factor for musculoskeletal pain in a population-based cohort of over 3000 English children (Deere et al., 2012). Furthermore, being obese increased the odds of any pain (odds ratio (OR) 1.3 3), regional pain (OR = 2.04), and knee pain (OR = 1.87) (Deere et al., 2012). Obese patien ts \200\231 average pain was also more severe than their non-obese counterparts (Deere et a l., 2012). Obesity was observed at a higher rate among youth presenting to a chronic pain c linic than a norma- tive sample (20.8% versus 9.6%), and youth with back pain in this sampl e had a rate of obesity of 57% (Wilson et al., 2010). Studies of younger children also use a variety of methodologies to evaluate the epidemiolog y of abdominal pain. In a Swedish study of 1155 6- to 13-year-olds, 39% experienced abdomin al pain monthly, 19% experienced abdominal pain weekly, and an additional 8% had it more th an once per week. Again girls experienced pain more oft en than boys (Petersen et al., 2003 ). In a population-based, retro- spective birth cohort study conducted with 5700 children l ess than 5 years of age in Rochester, Minnesota, 11% of the sample sought care for abdomina l pain at least three times within the fi rst 5 years of life (Chitkara et al., 2007). Fina lly a British study that defi ned RAP as fi ve or more episodes of pain over the previous y ear evaluated a cohort of almost 14 000 children. Th e prevalence of RAP increased from 3.8 % at 2.5 years, to 6.9% at 3.5 years, to 11.8% at 6.5 years (Ramchandani et al., 2005). For further discussion on recurrent abdominal pain, see Schurman (Chapter 29, this volume). Contextual factors in \202 uencing chronic recurrent pain As indicated in many of the prev iously discussed studies, there are several factors connected with the child and family tha t are associ- ated with chronic and recurrent pain in children. Th ese include: (1) age (e. g. where infants and adolescents oft en have higher preva- lence and lower pain management strategies implemented), (2) sex (e.g. where girls oft en have higher pain prevalence and i ntensity than boys), and (3) diagnosis (e.g. JIA and number of joints evalu- ated). Factors such as SES also infl uence pain with greater prev- alence of pain associated with lower S ES in some situations (e.g. oral/dental pain). Headache Headache is one of the most common pain complaints in children. Population studies of headache prevalence report that headache is frequently experienced by children and adol escents. Stanford et al. \200\231s (2008) study of almost 2500 Canadian adolescents found t hat prev- alence rates for weekly headache ranged from 26% to 31.8%, while 24.0% of America n adolescent girls experienced headache weekly (Ghandour et al., 2004). Diff erences in defi nitions of pain (e.g. acute, chronic, persistent, prolonged, recurrent ), in criteria for establishing pain diagnoses (e.g. International Headache Society criteri a, Apley and Naish criteria), research methods (retrospective chart review, prospec- tive s urvey or interview), data collection measures (whether validated or not), time or prevalenc e point, and reporting period also infl uence reported prevalence and pediatric pain distri bu- tion rates. SECTION 1 introduction 16 Chronic disease-related pain Sickle cell disease Pain is the most common symptom of sickle cell disease (SCD), and can begin early in the fi rst year of life as levels of fetal hemog lobin decline in susceptible individuals, but remains poorly character- ized. Th e frequenc y of pain episodes is consistently higher in the children who have hemoglobin SS or SB 0 th alassaemia compared with other genotypes. Most children with SCD have increasing pain episo des as well as pain-associated disability as they mature into adolescence and young adultho od. In a cohort of over 500 adults with SCD, 30% of respondents reported pain in greater th an 95% of diary days. While 70% of emergency department visits in children with SCD are for pain, the large majority of these painful episodes continue to be managed at home (Dampier et al., 2002a, 2002b). Pain episode frequency is correlated with mortality (Platt et al., 1991). Th e average pain episode is 2 to 9 days in duration. For further discussion on sick le cell disease, see Dampier and Barakat (Chapter 25, this volume). 2003) reported that all neonates underwent more than ten pain- ful procedures per day; thos e at the highest risk for neurological impairment had more procedures and received the leas t amount of analgesia during the fi rst days of life. In a pain diary study recorded of children with severe cogni- tive impairments over 2 weeks (n = 34), 73% of the children had a painful experience on at least 1 day (Stallard et al., 2001). In a longitudinal study, children with moderate to profound intellectual disability (n = 94) were found to experience pain for an average of 9 hour per week (Breau et al., 20 03). Th e majority of epidemiological studies in children with dis- ability have been performed in children with cerebral palsy (CP). Th e prevalence of pain with CP is between 50% and 75 % (Doralp and Bartlett, 2010; Parkinson et al., 2009; T z n et al., 2010). In a Europ ean study of 490 8- to 12-year-old children who could self- report and parents of 806 child ren (those who could and could not self-report), self-reported pain in the last week was 60 % with parent-reported pain in the last 4 weeks of 73% (Parkinson et al., 2009). Self-repor ted pain was more frequent in older children but was not associated with disability severit y, though parent-reported pain was associated with severity of disability. Other studies in CP have also found pain to be associated with severity of motor impairment (Houlihan et al ., 2004). In 68 children with spina bif- ida, 56% experienced pain at least once a week, in cluding headache in 88% with shunted hydrocephalus and 79% without hydrocepha- lus (Clancy et al., 2005). Juvenile idiopathic arthritis/juvenile rheumatoid arthritis Th e intensity of pain in JIA i s quite variable; however, pain is fre- quent. Children with JIA report pain on 70% of days (Schanberg et al., 2003). Most children reported mild to moderate pain, but 25% of childre n reported pain in the severe range. Disease status typically predicts only a small to medi um proportion of the variance in children \200\231s pain ratings (8 \200\22328%) (Malleson et al. 2004; Schanberg et al. 1997; Th ompson, 1987; Vandvik and Eckblad, 1990). Other vari ables such as demographic variables (possibly older age), psy- chological variables (such a s coping and mood), and environmental factors (parent pain history) also determine pain rep ort. For more on juvenile rheumatoid arthritis/JIA, see Chira and Schanberg (Chapter 22, th is volume). Th e most common type of pain among children with CP is mus- culoskeletal pain. Th e most c ommon sites of pain include feet, legs, back, hips, hands, and arms (Engel et al., 2005). M aximal pain is in the lower extremities in 70% of children (Ramstad et al., 2011). In addit ion, pain can result from commonly found secondary condi- tions including pressure ulcers a nd constipation. Implications for clinical practice, education, knowledge translation, and future research A lthough considerable variability and inconsistency exist amongst defi nitions for various t ypes of pain, measures and approaches to determining the prevalence of pain, and factors th at infl uence pain, overall acute and chronic pain is common, and oft en under- recognized and undertreated in infants, children, and adolescents. Th is issue persists in clinical an d community settings and includes hospitalized children who receive signifi cant numbers of painful procedures during their hospital stay, healthy children in the com- munity who are subjected to painful procedures associated with preventative/primary care (e.g. immunizati ons), and children with chronic illness who experience pain both while receiving care in th e community and during repeated periods of hospitalization. Cancer pain Pain is an almost universal symptom of childhood cancer, whether because of the disease itself, pain associated with treatment (mucosi- tis, abdominal pain, surgery, neur opathic pain), or procedural pain from procedures such as venous access, lumbar puncture, a nd bone marrow aspiration. In interviews with children, Ljungman et al. (1999) found treatm ent-related pain to be the most severe pain problem associated with cancer (49%) with fewer reporting procedure-related pain (39%) and disease-related pain (13%) as the most severe p ain problem. In a study of hospitalized children with cancer, more than half (27 of 49 pati ents) indicated they were expe- riencing pain. Eleven patients (22.4%) had mild pain, ten ( 20.4%) had moderate pain, and six (12.2%) had severe pain (Jacob et al., 2007). In a study of 164 youth dying from cancer, 92% experienced pain (Goldman et al., 2006). For cancer sur vivors, risk of report- ing pain conditions and using prescription analgesics in adulthood were higher than sibling controls (Lu et al., 2011). For more on can- cer pain, see Hickman et al. (Chapter 17, this volume). Decreasing the prevalence of pain requires increased eff orts in prevention and implementat ion of better pain assessment and management strategies in all health care settings. Succes s in these areas requires behavioral change on behalf of both health care professional and parent care providers. Furthermore, awareness of the prevalence of pediatric pain and imple mentation of eff ective knowledge translation (KT) strategies is required and needs to be s pecifi cally targeted to particular audiences. Eff ective implementa- tion of KT strategies requires a strong basis of evidence, a positive context where evidence is implemented (e.g . culture), and strategi- cally planned methods of facilitating the translation of evidence into Infants and children with disabilities In general, pain is common in children with disabili ties due to the underlying disease state, under-recognition of pain, and associa- tion with medical care needs. Stevens and colleagues (Stevens et al., CHAPTER 2 prevalence and distribution of pain in children 17 useful products for users (e.g. clinical practice guidelines for health care professionals and tips or fact sheets for parents). Champions for change and a wide array of KT strategie s including reminders, education, and audit and feedback for use in quality improvement ini tiatives are also required. An in-depth discussion of KT is pro- vided by Yamada and Hutchi nson (Chapter 61, this volume). the quality of existing research (such as by King et al., 2011), stand- ardize prevalance a nd pain defi nigions, and address areas which have received inadequate attention will assis t in making interpreta- tion of research results more meaningful and useful for both clini- cians and researchers. References Abu-Arefeh, I. and Russell, G. (1994). Prevalence of headache and migraine Research and evaluation form the basis for determining and reporting prevalence and distrib ution of pediatric pain and treat- ment. Th e research generally suff ers from both methodo logical and interpretation problems. From a methodological perspective, sam- ples are oft e n inadequate and limited to single settings or clinical sites. Additionally, approaches to assessing prevalence and report- ing period vary considerably and oft en non-validated/unte sted measures are used. Consistency in defi nition of types of pain, evaluation criteria, a pproach, measures, and timing of prevalence ratings would greatly enhance research in this area. Interpretation of results is oft en diffi cult due to methodological issues and incon - sistent or wide-ranging prevalence estimates, which impact on potential changes in practi ce. Further eff orts to critically evaluate in schoolchildren. BMJ, 309 (6957), 765 \200\223769 . Abu-Saad, H. H. (2010). Chronic pain in children and adolescents: a review. J Med Leban, 58 (2), 5 \200\223110 . Anand, K. J. S. and Selankio, J. D. (1996). SOPAIN Study Group: routine analgesia practices in 109 neonatal intensive care units (NICUs) . Pediatr Res , 39 , 192A . Apley, J. and Naish, N. (1958). Recurrent abdominal pains: a fi eld survey of 1000 school children. Arch Dis Child, 33 , 165 \200\223170 . Aromaa, M., Sillanapaa, M. L., Rautava, P., and Helenius, H. (1998). Childhood headache at school entry- controlled clinical trial. Neurology, 50 (6), 1729 \200\2231736 . Bakoula, C., Kapi, A., Veltsista, A., Kavadias, G., and Kolaitis, G. (2006). Prevalence of recurrent complaints of pain among Greek schoolchildren and associated factors: a populatio n-based study. Acta Paediatr, 95 (8), 947 \200\223951 . Case example Barea, L. M., Tannhauser, M., and Rotta, N. T. (1996). An epidemiologic study of headaches among children and adolescents of southern Brazil. Cephalalgia, 16 (8), 545 \200\223549 . Jackson is a 13-year-old boy who presents to his pediatrician with a 6-month history of epi sodic abdominal pain. Th e pain started the previous autumn. It comes on about 20 to 30 min utes aft er eating and is sometimes associated with diarrhea. Th ere is no blood in his sto ols; he has no fevers, or weight loss. His par- ents separated earlier this year. While his pain doesn \200\231t wake him from sleep he does have trouble falling asleep and will lie in bed for an hour or more several nights a week. Jackson has avoided going to friends \200 \231 houses because he is afraid he will have pain or diarrhea. He has missed over 2 weeks of school this year for abdominal complaints. Barker, D. and Rutter, N. (1995). Heel pricks were unnecessarily painful. BMJ , 311 (7007), 747 . Bille, B. (1997). A 40-year follow-up of school children with migraine. Cephalalgia , 17, 488 \200\22391. Bille, B. S. (1962). Migraine in school children. A study of the incidence and short-term p rognosis, and a clinical, psychological and electroencephalographic comparison between chil dren with migraine and matched controls. Acta Paediatr Suppl , 136, 1 \200\223151 . Boey, C. C. M., Yap, S. B., and Goh, K. L. (2000). Th e prevalence of recurrent abdominal p ain in 11- to 16-year-old Malaysian schoolchildren. J Paediatr Child Health , 36 (2), 114 \200\223116 . In a review of Jackson \200\231s pain history with his mother she describes several issues of pain in the past. As an infant Jackson had colic which resulted in several middle-of-the -night phone calls to his pediatrician. His parents learned to sooth him through these epis odes by running the vacuum cleaner in his room. Breau, L. M., Camfi eld, C. S., McGrath, P. J., and Finley, G. A. (2003). Th e incidence of pain in children with severe cognitive impairments. Arch Pediatr Adolesc Med, 157 (12), 12 19 \200\2231226 . Brun Sundblad, G. M., Saartok, T., and Engstr m, L. M. T. (2007). Prevalence and co-occu rrence of self-rated pain and perceived health in school- children: age and gender diff ere nces. Eur J Pain, 11 (2), 171 \200\223180 . Bugdayci, R., Ozge, A., Sasmaz, T., Oner Kurt, A., Kaleagasi, H., Karakelle, A., et al . (2 005). Prevalence and factors aff ecting headache in Turkish schoolchildren. Pediatr Int, 47 (3), 316 \200\223322 . When he was 3 years old, Jackson woke several times in the middle of the night with pain in his knees. He would cry out for his parents, they would give him ibuprofen, massage his ba ck, or, on occasion, put him in a warm bath. By his fi ft h birthday these episodes had res olved. Buskila, D., Neumann, L., Zmora, E., Feldman, M., Bolotin, A., and Press, J. (2003). Pain s ensitivity in prematurely born adolescents. Arch Pediatr Adolesc Med , 157 (11), 1079 \200 \22382 . Prior to starting school Jackson had developed a fear of receiv- ing his immunizations \200 \224a problem which persists to the present day. For his yearly fl u vaccination Jackson re ceives lidocaine prilocaine cream, and learned some guided imagery techniques from a family friend. His fear of needles extended to his interac- tions with his dentist and he require d general anesthesia to have three cavities fi lled. Campo, J. V., Di Lorenzo, C., Chiappetta, L., Bridge, J., Colborn, D. K., Gartner, J. C., e t al . (2001). Adult outcomes of pediatric recurrent abdominal pain: do they just grow out of it? Pediatrics , 108 (1), E1 . Carbajal, R., Rousset, A., Danan, C., Coquery, S., Nolent, P., Ducrocq, S., et al . (2008). Epidemiology and treatment of painful procedures in neonates in intensive care units. JAMA , 300 (1), 60 \200\22370 . Chitkara, D. K., Talley, N. J., Weaver, A. L., Katusic, S. K., De Schepper, H., Rucker, M. J., et al . (2007). Incidence of presentation of common functional gastrointestinal disorde rs in children from birth to 5 years: a cohort study. Clin Gastroenterol Hepatol, 5 (2), 18 6 \200\223191 . At age 11 Jackson collided with a teammate while playing soc- cer. He landed on his back. H e complained about pain in his lower back for several weeks before his parents sought medic al treatment. He was diagnosed with a muscular strain and received physical therapy for 2 m onths before he could return to full activ- ity without pain. Clancy, C. A., McGrath, P. J., and Oddson, B. E. (2005). Pain in children and adolescents with spina bifi da. Dev Med Child Neurol , 47 , 481 \200\22391 . Cummings, E. A., Reid, G. J., Finley, G. A., McGrath, P. J., and Ritchie, J. A. (1996). Pre valence and source of pain in pediatric inpatients. Pain , 68 (1), 25 \200\22331 . SECTION 1 introduction 18 Johnston, C. C., Collinge, J. M., Henderson, S., and Anand, K. J. (1997). A cross sectional survey of pain and analgesia in Canadian neonatal intensive care units. Clin J Pain , 3 (4 ), 1 \200\2235 . Dampier, C., Ely, B., Brodecki, D., and O \200\231Neal, P. (2002a). Characteristics of pain managed at home in children and adolescents with sickle cell disease by using diary self-r eports. J Pain, 3 (6), 461 \200\223470 . Johnston, C. C., Barrington, K. J., Taddio, A., Cabajal, R., and Filion, F. (2011). Pain in Canadian NICUs. Have we improved over the past 12 years? Clin J Pain, 27 (3), 225 \200\223 232 . Dampier, C., Ely, E., Brodecki, D., and O \200\231Neal, P. (2002b). Home management of pain in sickle cell disease: a daily diary study in children and adolescents. J Pediatr Hematol Oncol, 24 (8), 643 \200\223647 . Kashikar-Zuck, S., Goldschneider K. R., Powers, S. W., Vaught, M. H., and Hershey, A. D. (2 001). Depression and functional disability in chronic pediatric pain. Clin J Pain , 17 (4), 341 \200\2239 . Dangel, T. (2005). Management of chronic pain in children. Curr Paediatr , 15 , 69 \200\22374 . De Inocencio, J. (1998). Musculoskeletal pain in primary pediatric care: analysis of 1000 c onsecutive general pediatric clinic visits. Pediatrics, 102 (6), e63 \200\223e66 . Kaspiris, A. and Zafi ropoulou, C. (2009). Growing pains in children: epidemiological analy sis in a Mediterranean population. Joint Bone Spine, 76 , 486 \200\223490 . Deere, K. C., Clinch, J., Holliday, K., McBeth, J., Crawley, E. M., Sayers, A., et al . (20 12). Obesity is a risk factor for musculoskeletal pain in adolescents: fi ndings from a pop ulation cohort. Pain, 153 , 1932 \200\2231938 . Doralp, S. and Bartlett, D. J. (2010). Th e prevalence, distribution, and eff ect of pain among adolescents with cerebral palsy. Pedia tr Phys Th er, 22 (1), 26 \200\22333 . King, S., Chambers, C. T., Huguet, A., MacNevin, R. C., McGrath, P. J., Parker, L., et al . (2011). Th e epidemiology of chronic pain in children and adolescents revisited: a systema tic review. Pain , 152 (12), 2729 \200\2232738 . Kristj nsd ttir, G. (1996). Sociodem ographic diff erences in the prevalence of self-reported stomach pain in school children. E ur J Pediatr, 155 (11), 981 \200\223983 . Drossman, D. A. (2006). Th e functional gastrointestinal disorders and the Kroner-Herwig, B., Heinrich, M., and Morris, L. (2007). Headache in German children and ado lescents: a population-based epidemiological study. Cephalalgia, 27 (6), 519 \200\223527 . Rome III. Gastroenterology, 130 , 1377 \200\2231390 . Eccleston, C. and Crombez, G. (1999). Pain demands attention: a cognitive- aff ective model of the interruptive function of pain. Psychol Bull , 125 (3), 356 \200\22366 . Lim, C. S., Mayer-Brown, S. J., and Janicke, D. M. (2012). Th e impact of pain on physical activity and quality of life in obese children. Presented at the American Psychological Ass ociation Annual Convention, presidential track poster session, Orlando, FL , August. Ellis, J. A., O \200\231Connor, B. V., Cappelli, M., Goodman, J. T., Blouin, R., and Reid, C. W. (2002). Pain in hospitalized pediatric patients: how are we doing? Clin J Pain , 18(4 ), 262 \200\223269 . Ljungman, G., Gordh, T., Sorensen, S., and Kreuger, A. (1999). Pain in pediatric oncology: interviews with children, adolescents and their parents. Acta Paediatr, 88 (6), 623 \200 \223630 . El-Metwally, A., Salminen, J. J., Auvinen, A., Kautiainen, H., and Mikkelsson, M. (2005). L ower limb pain in a preadolescent population: prognosis and risk factors for chronicity \200\224a prospective 1- and 4-year follow-up study. Pediatrics, 116 (3), 673 \200\223681 . Lu, Q., Krull, K. R., Leisenring, W., Owen, J. E., Kawashima, T., Tsao, J. C., et al . (201 1). Pain in long-term adult survivors of childhood cancers and their siblings: a report fro m the Childhood Cancer Survivor Study. Pain, 152 (11), 2616 \200\2232624 . Engel, J. M., Petrina, T. J., Dugeon, B. J., and McKearnan, K. A. (2005). Cerebral palsy an d chronic pain: a descriptive study of children and adolescents. Phys Occup Th er Pediatr, 25 (4), 73 \200\22384 . Malleson, P. N., Oen, K., Cabral, D. A., Petty, R. E., Rosenberg, A. M., and Cheang, M. (20 04). Predictors of pain in children with established juvenile rheumatoid arthritis. Arthrit is Rheum, 51 (2), 222 \200\223227 . Evans, A. M. and Scutter, S. D. (2004). Prevalence of \200\230growing pains \200\231 in yo ung children. J Pediatr, 145 (2), 255 \200\2238 . Fernandez, C. V. and Rees, E. P. (1994). Pain management in Canadian level Masiero, S., Carraro, E., Sarto, D., Bonaldo, L., and Ferraro, C. (2010). Healthcare servic e use in adolescents with non-specifi c musculoskeletal pain. Acta P diatr, 99 , 1224 \200\2231228 . 3 neonatal intensive care units. CMAJ , 150 (4), 469 \200\223470 . Ghandour, R. M., Overpeck, M. D., Huang, Z. J., Kogan, M. D., and Scheidt, P. C. (2004). He adache, stomachache, backache, and morning fatigue among adolescent girls in the United Sta tes: associations with behavioral, sociodemographic, and environmental factors. Arch Pediat r Adolesc Med, 158 (8), 797 \200\223803 .