Effectiveness of a Preschool Motor Skill Intervention on Body Mass Index and Movement Behavior: 6-, 18-, and 30-Month Findings From a Cluster Randomized Controlled Trial.

PURPOSE: To study the effectiveness of a preschool staff-delivered motor skills intervention on body composition and physical activity over a 2.5-year time frame. METHODS: In this pragmatic parallel cluster randomized controlled trial (16 preschools), outcome data were collected after 6 (body composition only), 18, and 30 months of intervention. The main physical activity outcomes were accelerometer behavior measures summarizing the total percentage of child daily movement (walk, run, cycle, and standing that included minor movements) and preschool movement during preschool attendance. To estimate between-group mean differences in outcomes, mixed-linear regression analyses including baseline value of the selected outcome and a treatment × time interaction term as a fixed effect were applied. In addition, the baseline preschool and child were included as a random effect. RESULTS: For body mass index, a total of 437 children (90%) had at least one valid baseline and one follow-up assessment. The corresponding numbers for preschool movement and daily movement were 163 (55%) and 146 (49%), respectively. No significant between-group mean difference was identified for body mass index, waist-to-height ratio, or any physical activity outcomes. CONCLUSION: Overall, this preschool motor skills intervention had no effect on either child anthropometry or physical activity, consistent with previous studies.

Guideline adherence and socioeconomic factors in Danish patients referred to secondary care for low back pain: a cross sectional study.

BACKGROUND: The pre-referral history of patients with low back pain referred to secondary care is poorly documented, and it is unclear whether it complies with clinical guideline recommendations; specifically, whether they have received appropriate treatment in primary care. This study describes the patient population referred to a spine clinic at a Danish hospital and investigates whether they have received an adequate course of treatment in primary care before referral. Furthermore, a possible association between primary care treatment and socioeconomic factors is estimated. METHODS: We examined self-reported data from 1035 patients with low back pain of at least eight weeks duration referred to secondary care at a medical spine clinic using a cross-sectional design. As an approximation to national clinical guidelines, the definition of an adequate course of treatment in primary care was at least five visits to a physiotherapist or chiropractor prior to referral. RESULTS: Patients were on average 53 years old, and 56% were women. The average Oswestry Disability Index score was 36, indicating a moderate level of disability. Nearly half of the patients reported pain for over a year, and 75% reported pain below knee level. Prior to referral, 33% of the patients had not received an adequate course of treatment in primary care. Based on multiple logistic regression with the three socioeconomic variables, age and sex in the model, those who were unemployed had an odds ratio of 2.35 (1.15-4.79) for not receiving appropriate treatment compared to employed patients. Similarly, the odds ratio for patients without vs. with health insurance was 1.71 (1.17-2.50). No significant association was observed with length of education. CONCLUSIONS: Despite national clinical guidelines recommending management for low back pain in primary care, one third of the patients had not received an adequate course of treatment before referral to secondary care. Moreover, the high probability of not having received recommended treatment for patients who were unemployed or lacked health insurance indicates an economic obstacle to adequate care. Therefore, reconsidering the compensation structure for the treatment of back pain patients is imperative to mitigate health inequality within low back pain management.

Body height and spinal pain in adolescence: a cohort study from the Danish National Birth Cohort.

OBJECTIVES: To investigate how body height and trajectories of height from infancy through childhood and adolescence were associated with spinal pain in pre- and late adolescence. METHODS: This prospective study included 43,765 individuals born into The Danish National Birth Cohort (DNBC) from 1996 to 2003. DNBC-data were linked with health and social data identified from Statistics Denmark registers. Spinal pain was self-reported in both the 11-year- and 18-year follow-up of DNBC and classified according to severity. Body height was measured from birth and onwards and further modelled as distinct developmental height trajectories by using latent growth curve modelling. Associations were estimated by using multinomial logistic regression models. RESULTS: Taller body height in childhood and adolescence was associated with approximately 20% increased likelihood of spinal pain in pre- and late adolescence among girls compared to their peers in the normal height group. For boys, taller body height was associated with spinal pain by late adolescence only. Spinal pain in pre-adolescence almost doubled the likelihood of spinal pain in late adolescence regardless of body height at age 18. Height trajectories confirmed the relationship for girls with the tall individuals being most likely to have spinal pain in both pre- and late adolescence. CONCLUSION: Tall body height during childhood and adolescence predisposes to spinal pain among girls in both pre-and late adolescence, and among boys in late adolescence. Body height is a contributing factor to the pathogenesis of spinal pain in adolescence; however, the mechanisms may be related to growth velocity, but for now uncertain.

Exceeding 2-h sedentary time per day is not associated with moderate to severe spinal pain in 11- to 13-year-olds: a cross-sectional analysis.

Neck, mid-back and low back pain, collectively known as spinal pain, become more common with increasing age across childhood and adolescence. A common belief among the general community is that sedentary time, including screen time, in adolescents is associated with spinal pain. We aimed to investigate whether exceeding 2-h of sedentary time per day is associated with moderate to severe spinal pain in a sample of Danish adolescents aged 11-13 years. We performed a cross-sectional analysis of the SPACE study baseline data (2010). Adolescents self-reported their spinal pain (outcome) via the Young Spine Questionnaire and duration of engagement in sedentary behaviours (exposure). We provide estimates of associations as odds ratios with 95% confidence intervals, stratified by age and sex. The sample comprised 1,303 adolescents (48.7% female, mean age 12.5 years, range 10.9-14.3 years). Approximately 9 out of 10 adolescents exceeded 2-h sedentary time on weekdays outside of school (88.9%) and weekend days (89.9%). Close to one-quarter, 23.3% (95%CI: 21.0-25.6), of participants experienced moderate to severe spinal pain. We found no association between exceeding 2-h sedentary time per day and experiencing moderate to severe spinal pain; odds ratios ranged from 0.34 (95%CI: 0.04-3.20) to 4.65 (95%CI: 0.26-82.44).Conclusion: We found no association between exceeding 2- or 5-h of sedentary time per day and moderate to severe spinal pain in this sample of 11-13-year-old Danish adolescents. Our cross-sectional analysis does not consider the longitudinal or complex sequences of events necessary to address predictive or causal questions. What is Known: • Up to a third of adolescents experience moderate to severe spinal pain, predisposing them to chronic spinal pain in adulthood. • Frequent and excessive sedentary time is associated with poor overall health in adolescents; there is conflicting evidence to suggest whether it is also related to spinal pain. What is New: • We found no association between sedentary time and moderate to severe spinal pain in 11- to 13-year-old Danes.

Spinal pain in childhood: prevalence, trajectories, and diagnoses in children 6 to 17 years of age.

This study aimed to investigate the trajectories of spinal pain frequency from 6 to 17 years of age and describe the prevalence and frequency of spinal pain and related diagnoses in children following different pain trajectories. First through fifth-grade students from 13 primary schools were followed for 5.5 years. Occurrences of spinal pain were reported weekly via text messages. Children reporting spinal pain were physically evaluated and classified using International Classification of Disease criteria. Trajectories of spinal pain frequency were modeled from age 6 to 17 years with latent class growth analysis. We included data from 1556 children (52.4% female, mean (SD) baseline age = 9.1 (1.9) years) and identified 10,554 weeks of spinal pain in 329,756 weeks of observation. Sixty-three percent of children reported one or more occurrences of spinal pain. We identified five trajectories of spinal pain frequency. Half the children (49.8%) were classified as members of a "no pain" trajectory. The remaining children followed "rare" (27.9%), "rare, increasing" (14.5%), "moderate, increasing" (6.5%), or "early-onset, decreasing" (1.3%) spinal pain trajectories. The most common diagnoses in all trajectory groups were non-specific (e.g., "back pain"). Tissue-specific diagnoses (e.g., muscle strain) were less common and pathologies (e.g., fracture) were rare.  Conclusion: From childhood through adolescence, spinal pain was common and followed heterogeneous courses comprising stable, increasing, and early-onset trajectories. These findings accord with recommendations from adult back pain guidelines that most children with spinal pain can be reassured that they do not have a serious disease and encouraged to stay active. What is Known: • Spinal pain imposes a large burden on individuals and society. • Although many people first experience the condition in childhood, little is known about the developmental trajectories of spinal pain from childhood to adolescence. What is New: • Data from 1556 children and 329,756 participant weeks showed five unique spinal pain trajectories from 6 to 17 years: most children rarely reported spinal pain, while one in five followed increasing or early-onset trajectories. • Most pain occurrences were non-specific; pathological diagnoses were rare.

Physical impairments among adults in Denmark: a register-based study.

BACKGROUND: Knowledge of the prevalence and socio-demographic characteristics of physical impairments is limited. This study aimed to determine the prevalence of physical impairments among adults in Denmark, both in total and according to nine common diagnostic subgroups, describe the socio-demographic and socio-economic profile, and compare the data with those of the general adult population. METHODS: This descriptive, cross-sectional, register-based study evaluated the general socio-demographic and socio-economic variables, including sex, age, geographical region, origin, educational level, occupation, marital status, and disability level, of adults with physical impairments extracted by diagnosis from the Danish National Patient Register and Statistics Denmark by 31 December 2018. These data were compared with those of the general adult population in Denmark extracted from Statistics Denmark by January 2019. RESULTS: In total, 606,857 adults with physical impairments were identified. Of the nine selected diagnoses, osteoarthritis (69.4%) was the most prevalent, followed by acquired brain injury (29.0%), rheumatoid arthritis (6.7%), multiple sclerosis (2.6%), spinal cord injury (1.5%), cerebral palsy (1.2%), amputation (0.7%), muscular dystrophy (0.5%), and poliomyelitis (< 0.1%). There were large variations in the socio-demographic and socio-economic profile between the nine diagnostic subgroups. The adults with physical impairments were more often women, were older, were less often immigrants and employed adults, had a lower educational level, and were more commonly married than the general adult population. Only the geographical region did not differ. CONCLUSION: The nine subgroups with diagnoses related to the musculoskeletal system represent 13% of the adult Danish population. The socio-demographic and socio-economic profile varied largely between the nine diagnostic subgroups, and almost all variables differed significantly between adults with physical impairments and the general adult population in Denmark. These findings reveal patterns and trends on socio-demographic and socio-economic variables essential for future planning at a societal level, including the healthcare and social sectors.

Spinal pain in pre-adolescence and the relation with screen time and physical activity behavior.

BACKGROUND: To investigate how screen time and physical activity behavior were associated with spinal pain in pre-adolescence. METHODS: This study included 45,555 pre-adolescents who participated in the 11-year follow-up of the Danish National Birth Cohort. The 11-year follow-up included self-reported information on computer and TV behavior, aspects of physical activity, as well as frequency and intensity of spinal pain (neck-, mid back- and low back pain). Data were linked with parental socioeconomic data from Statistics Denmark registers. Associations were estimated using multinomial logistic regression models. To account for sample selection, we applied inverse probability weighting. RESULTS: Duration of screen time was stepwise associated with the degree of spinal pain. Compared with those spending < 2 h/day in front of a screen, screen time of ≥6 h/day was associated with a substantially increased relative risk ratio (RRR) of severe pain for both girls (RRR: 2.49, 95% CI: 2.13-2.92) and boys (RRR: 1.95, 95% CI: 1.65-2.32). Being physical inactive was likewise associated with higher likelihood of severe spinal pain (RRR: 1.22, 95% CI: 1.10-1.34) relative to those being moderately active. We observed that being physically active was seemingly associated with lower risk of spinal pain among boys with high frequency of screen time. CONCLUSION: Findings indicate that both duration of screen time and physical inactivity are correlated with spinal pain in pre-adolescents with the strongest associations for screen time. Reducing screen time or increasing physical activity might help preventing spinal pain in pre-adolescents, particularly among high frequent screen users. Future prospective studies investigating the causal relationship are necessary.

Baseline Characteristics May Help Indicate the Best Choice of Health Care Provider for Back Pain Patients in Primary Care: Results From a Prospective Cohort Study.

OBJECTIVE: Baseline characteristics of patients low back pain differ substantially between care settings, but it is largely unknown whether predictors are of equal importance across settings. The aim of this study was to investigate whether 8 known predictors relate differently to outcomes in chiropractic practice and in general practice and to which degree these factors may be helpful in selecting patients benefiting more from one setting or the other. METHODS: Patient characteristics were collected at baseline, and outcomes of pain intensity (numeric rating scale 0-10) and activity limitation (Roland-Morris Disability Questionnaire 0-100) after 2, 12, and 52 weeks. Differences in the prognostic strength between settings were investigated for each prognostic factor separately by estimating the interaction between setting and the prognostic factor using regression models. Between-setting differences in outcome in high-risk and low-risk subgroups, formed by single prognostic factors, were assessed in similar models adjusted for a propensity score to take baseline differences between settings into account. RESULTS: Prognostic factors were generally associated more strongly with outcomes in general practice compared with chiropractic practice. The difference was statistically significant for general health, duration of pain, and musculoskeletal comorbidity. After propensity score adjustment, differences in outcomes between settings were insignificant, but negative prognostic factors tended to be less influential in chiropractic practice except for leg pain and depression, which tended to have less negative impact in general practice. CONCLUSION: Known prognostic factors related differently to outcomes in the 2 settings, suggesting that some subgroups of patients might benefit more from one setting than the other.

Early-life programming of pain sensation? Spinal pain in pre-adolescents with pain experience in early life.

Neurobiological mechanisms can be involved in early programming of pain sensitization. We aimed to investigate the association between early-life pain experience and pre-adolescence spinal pain. We conducted a study of 29,861 pre-adolescents (age 11-14) from the Danish National Birth Cohort. As indicators of early-life pain, we used infantile colic and recurrent otitis media, reported by mothers when their children were 6 and 18 months. Self-reported spinal pain (neck, middle back, and/or low back pain) was obtained in the 11-year follow-up, classified according to severity. Associations between early-life pain and spinal pain in pre-adolescents were estimated using multinomial logistic regression models. To account for sample selection, inverse probability weighting was applied. Children experiencing pain in early life were more likely to report severe spinal pain in pre-adolescence. The association appeared stronger with exposure to two pain exposures (relative risk ratio, 1.31; 95% CI, 1.02-1.68) rather than one (relative risk ratio, 1.14; 95% CI, 1.05-1.24). We observed similar results when using headache and abdominal pain as outcome measures, underpinning a potential neurobiological or psychosocial link in programming of pain sensitization.Conclusion: Experience of early-life pain is seemingly associated with spinal pain in pre-adolescence. The study highlights that early-life painful experiences can influence programming of future pain responses.What is Known:• Spinal pain in pre-adolescents is common, causes marked discomfort and impairment in everyday life, and may be an important predictor of spinal pain later in life.• Neurobiological mechanisms have been suggested as involved in early programming of pain sensitization.What is New:• Pain exposure in early postnatal life in terms of infantile colic and recurrent otitis media is associated with spinal pain in pre-adolescence; thus, experience of such painful conditions in the early postnatal period may seemingly influence programming of future pain sensation.

The association between psychological and social factors and spinal pain in adolescents.

Spinal pain, back pain, and/or neck pain begins early in life and is strongly associated with spinal pain in adulthood. Understanding the relationship between psychological and social factors and adolescent spinal pain may be important in both the prevention and treatment of spinal pain in this age group. We aimed to determine if psychological and social factors were associated with spinal pain in a cross-sectional study of a school-based cohort of 1279 Danish adolescents aged 11-13, who were categorized into "any" and "substantial" spinal pain. "Substantial spinal pain" was defined as a lifetime frequency of "sometimes" or "often" and a pain intensity of at least two on the revised Faces Pain Scale. Logistic regression analyses, stratified by sex, were conducted for single and all variables together. Eighty-six percent of participants reported "any spinal pain" and 28% reported "substantial spinal pain". Frequency of psychological and social factors was significantly higher in those with spinal pain compared to those without. As the frequency of psychological and social factors increased, the odds of both "any spinal pain" and "substantial spinal pain" also increased.Conclusion: Psychological and social factors may be important determinants in adolescent spinal pain. What is Known: • Spinal pain begins early in life to reach adult levels by age 18. Spinal pain in adolescence is strongly associated with spinal pain in adulthood. • In adults, psychological and social factors and spinal pain are strongly related; however, this relationship in adolescence is poorly understood. What is New: • Adolescents with spinal pain reported a significantly higher frequency of psychological factors and loneliness and lower levels of pupil acceptance. • Adolescents reporting higher levels of loneliness, lower levels of pupil acceptance, and increased frequency of psychological factors had increased odds of reporting "substantial spinal pain".

Epidemiology of spinal pain in children: a study within the Danish National Birth Cohort.

This study aims to describe the prevalence of spinal pain among Danish children, explore the differential nature of spinal pain, and investigate socio-demographic factors predisposing spinal pain. A descriptive study of 46,726 11-14-year-olds participating in the Danish National Birth Cohort was conducted. Self-reported spinal pain (neck, middle back, and low back pain) was registered and classified according to severity. Socioeconomic data on children and their parents were identified in Statistics Denmark registers. Associations between socio-demographic factors and aspects of spinal pain were estimated using multinomial logistic regression models. To account for sample selection, inverse probability weighting (IPW) was applied. Almost 10% boys and 14% girls reported severe spinal pain, whereas around 30% of all children reported moderate pain. Effect estimates indicated the risk to increase with increasing age. Further, children without biological full siblings, not living with both of their parents, or children living in less-educated or lower-income families were more likely to experience spinal pain. The study conclusions were essentially unaffected by IPW.Conclusion: A considerable number of children suffer from spinal pain, and it is more common among children in more disadvantaged families. Etiology of spinal pain needs to be explored further with the aim of informing efficient and targeted prevention. What is Known: • Childhood spinal pain may cause marked discomfort and impairment in children's everyday life, and is suggested as important predictor of later-in-life spinal pain. • Methodological heterogeneity in previous studies and complexity of measuring pain make inferences at a broader level inadequate. What is New: • Prevalence of severe spinal pain in 11-14-year-olds was estimated to almost 10% for boys and 14% for girls, and children in more disadvantaged families were more likely to experience spinal pain. • The results seemed unaffected by sample selection.

Pubertal development and growth are prospectively associated with spinal pain in young people (CHAMPS study-DK).

PURPOSE: To examine the prospective associations of pubertal development and linear growth with spinal pain frequency and duration in children. METHODS: We recruited students from 10 public primary schools. Over 42 months, pubertal development was assessed four times and categorized according to Tanner stages 1-5, and height was measured on seven occasions. Occurrences of spinal pain were reported weekly via text messaging. We constructed variables for spinal pain duration (total weeks with pain) and frequency (number of episodes). Potential associations between pubertal development and growth were examined with generalized estimating equations and reported with incident rate ratios (IRRs). All models were adjusted for potential confounders. RESULTS: Data from 1021 children (53% female; mean [SD] age = 9.4 [1.4] years), with median participation duration of 39 months, were included. Advancing pubertal development was associated with increased spinal pain duration (IRR [95% CI] = 1.90 [1.45, 2.49] to 5.78 [4.03, 8.29]) and frequency of pain episodes (IRR [95% CI] = 1.32 [1.07, 1.65] to 2.99 [2.24, 3.98]). Similar associations were observed for each 1-cm change in height in 6 months with spinal pain duration (IRR [95% CI] = 1.19 [1.15, 1.23]) and frequency (IRR [95% CI] = 1.14 [1.11, 1.17]). The relations between pubertal development and spinal pain, as well as growth and spinal pain, were largely independent. CONCLUSIONS: In young people, pubertal development and linear growth are likely to be independent risk factors for the development of spinal pain. Pubertal development demonstrates evidence of dose-response in its relationship with spinal pain. This knowledge may assist healthcare providers with clinical decision-making when caring for pediatric patients. These slides can be retrieved under Electronic Supplementary Material.

Does lower extremity pain precede spinal pain? A longitudinal study.

The main objective was to investigate whether children aged 9-15 years at baseline were more likely to experience an incident event of spinal pain after experiencing lower extremity pain. Children's musculoskeletal pain was monitored by weekly mobile phone text message responses from parents, indicating whether the child had spinal pain, lower extremity pain, or upper extremity pain the preceding week. Data were analyzed using mixed effect logistic regression models and cox regression models. The association between an incident event of spinal pain and LE pain the preceding weeks increased with increasing observation period and was statistically significant for 12 and 20 weeks (OR = 1.34 (95% CI 1.05 to 1.70) and OR = 1.39 (95% CI 1.11 to 1.75), respectively). We found that the likelihood increased in children with more frequent or longer duration of lower extremity pain. The reversed relationship was investigated as well, and we also found a positive association between spinal pain and a subsequent incidence event of lower extremity pain, but less pronounced.Conclusion: Children were more likely to experience an incident event of spinal pain after experiencing lower extremity pain. The likelihood increased in children with more frequent or longer duration of lower extremity pain. What is Known: • Both spinal pain and lower extremity pain often start early in life and is common already in adolescence. What is New: • Children were more likely to experience an incident event of spinal pain after experiencing LE pain. • The likelihood increased in children with more frequent or longer duration of LE pain.

Spinal pain and co-occurrence with stress and general well-being among young adolescents: a study within the Danish National Birth Cohort.

This study aims to describe the patterns in low back, mid back, and neck pain complaints in young adolescents from the Danish National Birth Cohort (DNBC) and to investigate the co-occurrence of spinal pain and stress and general well-being, respectively. Cross-sectional data from the 11-year follow-up of DNBC were used. As part of a web-based survey, a total of 45,371 young adolescents between 10 and 14 years old completed the Young Spine Questionnaire, the Stress in Children Questionnaire, and a one-item question on general well-being. Associations between spinal pain and, respectively, stress and general well-being were estimated by means of multiple logistic regression models. Almost one fifth of boys and one quarter of girls reported spinal pain. Compared with adolescents who reported no stress, adolescents reporting medium and high values of stress had odds ratios (OR) of 2.19 (95% CI 2.08-2.30) and 4.73 (95% CI 4.28-5.23), respectively, of reporting spinal pain (adjusted for age, gender, and maternal education). Adolescents who reported poor general well-being had an OR of 2.50 (95% CI 2.31-2.72) for reporting spinal pain compared to adolescents with good general well-being. CONCLUSION: Spinal pain is a common complaint among young adolescents and co-occurs with stress and poor general well-being. The mutual dependency between the factors remained to be explained. What is Known: • The prevalence of spinal pain increases rapidly during childhood and adolescence, but different measurement instruments result in great variation in the estimates of spinal pain in children and adolescents. • Some studies have shown that different psychosocial measures are associated with spinal pain in children and adolescents. What is New: • Spinal pain, as measured by the newly developed and validated Young Spine Questionnaire, is a common complaint in young adolescents aged 10-14 years. • Spinal pain in young adolescents co-occurs with stress and poor general well-being.

Prevalence and incidence of musculoskeletal extremity complaints in children and adolescents. A systematic review.

BACKGROUND: It is difficult to gain an overview of musculoskeletal extremity complaints in childhood although this is essential to develop evidence-based prevention and treatment strategies. The objectives of this systematic review were therefore to describe the prevalence and incidence of musculoskeletal extremity complaints in children and adolescents in both general and clinical populations in relation to age, anatomical site and mode of onset. METHODS: MEDLINE and EMBASE were electronically searched; risk of bias was assessed; and data extraction was individually performed by two authors. RESULTS: In total, 19 general population studies and three clinical population studies were included with children aged 0-19 years. For most of the analyses, a division between younger children aged 0-12 years, and older children aged 10-19 years was used. Lower extremity complaints were more common than upper extremity complaints regardless of age and type of population, with the most frequent pain site changing from ankle/foot in the youngest to knee in the oldest. There were about twice as many non-traumatic as traumatic complaints in the lower extremities, whereas the opposite relationship was found for the upper extremities in the general population studies. There were relatively more lower extremity complaints in the general population studies than in the clinical population studies. The review showed no pattern of differences in reporting between studies of high and low risk of bias. CONCLUSIONS: This review shows that musculoskeletal complaints are more frequent in the lower extremities than in the upper extremities in childhood, and there are indications of a large amount of non-traumatic low intensity complaints in the population that do not reach threshold for consultation. A meta-analysis, or even a simple overall description of prevalence and incidence of musculoskeletal extremity complaints in children and adolescents was not feasible, due to a large variety in the studies, primarily related to outcome measurements.

How can latent trajectories of back pain be translated into defined subgroups?

BACKGROUND: Similar types of trajectory patterns have been identified by Latent Class Analyses (LCA) across multiple low back pain (LBP) cohorts, but these patterns are impractical to apply to new cohorts or individual patients. It would be useful to be able to identify trajectory subgroups from descriptive definitions, as a way to apply the same definitions of mutually exclusive subgroups across populations. In this study, we investigated if the course trajectories of two LBP cohorts fitted with previously suggested trajectory subgroup definitions, how distinctly different these subgroups were, and if the subgroup definitions matched with LCA-derived patterns. METHODS: Weekly measures of LBP intensity and frequency during 1 year were available from two clinical cohorts. We applied definitions of 16 possible trajectory subgroups to these observations and calculated the prevalence of the subgroups. The probability of belonging to each of eight LCA-derived patterns was determined within each subgroup. LBP intensity and frequency were described within subgroups and the subgroups of 'fluctuating' and 'episodic' LBP were compared on clinical characteristics. RESULTS: All of 1077 observed trajectories fitted with the defined subgroups. 'Severe episodic LBP' was the most frequent pattern in both cohorts and 'ongoing LBP' was almost non-existing. There was a clear relationship between the defined trajectory subgroups and LCA-derived trajectory patterns, as in most subgroups, all patients had high probabilities of belonging to only one or two of the LCA patterns. The characteristics of the six defined subgroups with minor LBP were very similar. 'Fluctuating LBP' subgroups were significantly more distressed, had more intense leg pain, higher levels of activity limitation, and more negative expectations about future LBP than 'episodic LBP' subgroups. CONCLUSION: Previously suggested definitions of LBP trajectory subgroups could be readily applied to patients' observed data resulting in subgroups that matched well with LCA-derived trajectory patterns. We suggest that the number of trajectory subgroups can be reduced by merging some subgroups with minor LBP. Stable levels of LBP were almost not observed and we suggest that minor fluctuations in pain intensity might be conceptualised as 'ongoing LBP'. Lastly, we found clear support for distinguishing between fluctuating and episodic LBP.

Latent class analysis derived subgroups of low back pain patients - do they have prognostic capacity?

BACKGROUND: Heterogeneity in patients with low back pain is well recognised and different approaches to subgrouping have been proposed. One statistical technique that is increasingly being used is Latent Class Analysis as it performs subgrouping based on pattern recognition with high accuracy. Previously, we developed two novel suggestions for subgrouping patients with low back pain based on Latent Class Analysis of patient baseline characteristics (patient history and physical examination), which resulted in 7 subgroups when using a single-stage analysis, and 9 subgroups when using a two-stage approach. However, their prognostic capacity was unexplored. This study (i) determined whether the subgrouping approaches were associated with the future outcomes of pain intensity, pain frequency and disability, (ii) assessed whether one of these two approaches was more strongly or more consistently associated with these outcomes, and (iii) assessed the performance of the novel subgroupings as compared to the following variables: two existing subgrouping tools (STarT Back Tool and Quebec Task Force classification), four baseline characteristics and a group of previously identified domain-specific patient categorisations (collectively, the 'comparator variables'). METHODS: This was a longitudinal cohort study of 928 patients consulting for low back pain in primary care. The associations between each subgroup approach and outcomes at 2 weeks, 3 and 12 months, and with weekly SMS responses were tested in linear regression models, and their prognostic capacity (variance explained) was compared to that of the comparator variables listed above. RESULTS: The two previously identified subgroupings were similarly associated with all outcomes. The prognostic capacity of both subgroupings was better than that of the comparator variables, except for participants' recovery beliefs and the domain-specific categorisations, but was still limited. The explained variance ranged from 4.3%-6.9% for pain intensity and from 6.8%-20.3% for disability, and highest at the 2 weeks follow-up. CONCLUSIONS: Latent Class-derived subgroups provided additional prognostic information when compared to a range of variables, but the improvements were not substantial enough to warrant further development into a new prognostic tool. Further research could investigate if these novel subgrouping approaches may help to improve existing tools that subgroup low back pain patients.

Identifying subgroups of patients using latent class analysis: should we use a single-stage or a two-stage approach? A methodological study using a cohort of patients with low back pain.

BACKGROUND: Heterogeneity in patients with low back pain (LBP) is well recognised and different approaches to subgrouping have been proposed. Latent Class Analysis (LCA) is a statistical technique that is increasingly being used to identify subgroups based on patient characteristics. However, as LBP is a complex multi-domain condition, the optimal approach when using LCA is unknown. Therefore, this paper describes the exploration of two approaches to LCA that may help improve the identification of clinically relevant and interpretable LBP subgroups. METHODS: From 928 LBP patients consulting a chiropractor, baseline data were used as input to the statistical subgrouping. In a single-stage LCA, all variables were modelled simultaneously to identify patient subgroups. In a two-stage LCA, we used the latent class membership from our previously published LCA within each of six domains of health (activity, contextual factors, pain, participation, physical impairment and psychology) (first stage) as the variables entered into the second stage of the two-stage LCA to identify patient subgroups. The description of the results of the single-stage and two-stage LCA was based on a combination of statistical performance measures, qualitative evaluation of clinical interpretability (face validity) and a subgroup membership comparison. RESULTS: For the single-stage LCA, a model solution with seven patient subgroups was preferred, and for the two-stage LCA, a nine patient subgroup model. Both approaches identified similar, but not identical, patient subgroups characterised by (i) mild intermittent LBP, (ii) recent severe LBP and activity limitations, (iii) very recent severe LBP with both activity and participation limitations, (iv) work-related LBP, (v) LBP and several negative consequences and (vi) LBP with nerve root involvement. CONCLUSIONS: Both approaches identified clinically interpretable patient subgroups. The potential importance of these subgroups needs to be investigated by exploring whether they can be identified in other cohorts and by examining their possible association with patient outcomes. This may inform the selection of a preferred LCA approach.