Inmaculada Calvo-Muñoz, Antonia Gómez-Conesa, and Julio Sánchez-Meca
Faculty of Medicine, Espinardo Campus,
University of Murcia,
Murcia, 30100, Spain.
BACKGROUND: Low back pain (LBP) is common in children and adolescents, and it is becoming a public health concern. In recent years there has been a considerable increase in research studies that examine the prevalence of LBP in this population, but studies exhibit great variability in the prevalence rates reported. The purpose of this research was to examine, by means of a meta-analytic investigation, the prevalence rates of LBP in children and adolescents.
METHODS: Studies were located from computerized databases (ISI Web of Knowledge, MedLine, PEDro, IME, LILACS, and CINAHL) and other sources. The search period extended to April 2011. To be included in the meta-analysis, studies had to report a prevalence rate (whether point, period or lifetime prevalence) of LBP in children and/or adolescents (≤ 18 years old). Two independent researchers coded the moderator variables of the studies, and extracted the prevalence rates. Separate meta-analyses were carried out for the different types of prevalence in order to avoid dependence problems. In each meta-analysis, a random-effects model was assumed to carry out the statistical analyses.
RESULTS: A total of 59 articles fulfilled the selection criteria. The mean point prevalence obtained from 10 studies was 0.120 (95% CI: 0.09 and 0.159). The mean period prevalence at 12 months obtained from 13 studies was 0.336 (95% CI: 0.269 and 0.410), whereas the mean period prevalence at one week obtained from six studies was 0.177 (95% CI: 0.124 and 0.247). The mean lifetime prevalence obtained from 30 studies was 0.399 (95% CI: 0.342 and 0.459). Lifetime prevalence exhibited a positive, statistically significant relationship with the mean age of the participants in the samples and with the publication year of the studies.
CONCLUSIONS: The most recent studies showed higher prevalence rates than the oldest ones, and studies with a better methodology exhibited higher lifetime prevalence rates than studies that were methodologically poor. Future studies should report more information regarding the definition of LBP and there is a need to improve the methodological quality of studies.
From the FULL TEXT Article
The term low back pain (LBP) was defined by Andersson  as “pain limited to the region between the lower margins of the 12th rib and the gluteal folds”. LBP is the most common type of back pain , occurring in about 60–80% of people at some point in their lives .
LBP often begins in childhood, and in adolescents the prevalence is similar to that of adults [4, 5]. One characteristic of LBP in childhood and adolescence is its high recurrence and the tendency to reappear with greater intensity . Although initially intensity is usually low  and it generally lasts for less than a week [7, 8], LBP causes limitations in carrying out activities , school absenteeism and the reduction or ceasing of physical activity .
In recent years there has been a considerable increase in research studies that examine the prevalence of LBP in this population [7, 10-16], but studies exhibit great variability in prevalence rates, with estimates ranging from 1.1%  to 66% .
This variability found in the prevalence estimates may be due to differences among the studies in such factors as the age of the sample, the sample size, the definition of LBP, the LBP recall period, the strategy for extracting data and the methodology used.
The prevalence of a condition is the number of cases in a specified population at a particular time . The prevalence is described in terms such as: point prevalence (the number of persons in a defined population who had a specified disease or condition at a particular point in time, usually the time the survey was carried out), period prevalence (the number of persons who had a specified disease or condition at any time during a specified time interval), and lifetime prevalence (the number of persons who had a specified disease or condition at some point in their life) .
According to the literature on the epidemiology of LBP in children and adolescents, the prevalence rates increase with the age of the subjects [11, 19-21] and females have higher prevalence rates than males [12, 16, 22-24]. Epidemiological studies indicate that the point prevalence is less than the period prevalence and, in turn, this is less than the lifetime prevalence [12, 25, 26].
Several narrative reviews have been published about the prevalence of LBP in children and adolescents [27-29]. However, to our knowledge, a meta-analysis of the LBP prevalence in children and adolescents has not yet been carried out. Thus, the main purpose of this research was to systematically review the prevalence of LBP obtained in studies with samples composed by children and/or adolescents, in order to: (a) obtain estimates of point, period, and lifetime prevalence rates; (b) determine whether the heterogeneity exhibited by the prevalence rates of the studies can be explained by random sampling alone or, on the contrary, the studies present very discrepant prevalence rates, and (c) in the latter case, to search for substantive and methodological characteristics of the studies that can explain this heterogeneity.
Based on the results of previous research, several hypotheses were raised: (a) the mean estimate of point prevalence will be lower than that of period prevalence and, in turn, this will be lower than that of lifetime prevalence; (b) the prevalence rates will increase with the age of the participants in the samples, and (c) females will present higher prevalence rates than males.
The aim of this research was to examine, by means of a meta-analytic investigation, the prevalence rates of LBP in children and adolescents, as well as to search for characteristics of the studies that can explain the heterogeneity exhibited by the prevalence rates. With this purpose, a total of 59 studies fulfilled our selection criteria and were included in our meta-analysis.
The results confirmed the hypothesis that the lifetime prevalence is higher than the period prevalence and, in turn this is higher than the point prevalence. These results coincide with those obtained by Louw et al.  that detected mean LBP point, one-year, and lifetime prevalences for adolescents of 12%, 33%, and 36%, respectively.
The hypothesis that the prevalence rate would increase with the age of the participants in the samples was confirmed by our results. These findings are in line with those obtained by Balagué et al.  and Jones et al. . Balagué et al.  reported lifetime prevalences of 16% and 58% for children and adolescents, respectively, and Jones et al.  reported lifetime prevalences of 18.2% for 10 years old children and of 65.6% for 16 year old adolescents.
With regards to gender, authors such as Shebad et al.  and Kovacs et al.  found higher lifetime prevalences for women (64.7% and 69.3%, respectively) than for men (50.8% and 50.9%, respectively). On the contrary, Newcomer et al.  reported higher prevalence rates for men than for women (57% and 44%, respectively). Finally, Olsen et al.  did not find relevant differences between the lifetime prevalence rates for men and women (30.7% and 30%, respectively). The results of our meta-analysis exhibited a nonstatistically significant relationship between gender and lifetime prevalence and, as a consequence, our hypothesis of a larger prevalence for women than for men was not confirmed.
The large heterogeneity found in all types of prevalence indicates the existence of characteristics of the studies causing this variability. The publication year influenced the lifetime prevalence rates, with the higher prevalence rates being reported in the most recent studies. This result seems to be very solid, as in the multiple meta-regression model publication year was one of the two predictors that achieved a statistically significant relationship with the lifetime prevalence, once controlled the methodological quality of the studies, the delimitation of pain, and the mean age of the sample. However, what our analyses do not enable us to determine are the reasons of that increase in the prevalence rates. Thus, it could be that children are changing their activity level or they are more overweight; it could be that the actual prevalence has not changed but the reporting has; or it could be that the questions used to assess the prevalence have changed. This point would need more research. Regarding the methodological quality of the studies, the studies with a better quality tended to show higher lifetime prevalence rates than studies that were methodologically poor.
The most common methodological shortcomings of the studies included in the review were the lack of a clear definition and delimitation of LBP and the absence of important specifications of LBP such as the frequency of episodes, its intensity and duration. In particular, out of the studies published between 1980 and 2001, only 40.9% reported a clear definition of LBP, whereas in the most recent studies (from 2002 to date) this percentage was 73%. With regards to the LBP specifications, the percentage was 71% for studies published in the last 10 years and 29% for those that were not published in the last 10 years.
Limitations of the meta-analysis
It is important to note some limitations of our meta-analysis. The small number of studies that reported point and period prevalence rates discouraged the analysis of moderator variables and, as a consequence, this kind of analysis was applied for lifetime prevalence rates only. On the other hand, the absence of a more detailed description in the primary studies about such important aspects as the exact area of pain caused uncertainty in our coding process.
Implications for clinical practice
The results of our meta-analysis have important consequences for professionals. Our finding of higher prevalence rates in the most recent studies suggests that LBP is a problem that is increasing in childhood and adolescence. As a consequence, more attention should be devoted to develop and apply prevention programs for young children in order to break this trend. On the other hand, our finding of higher prevalence rates in the studies with older subjects points to the need for efforts towards an early detection of LBP in children and adolescents.
Implications for future research
Our results enable us to make recommendations for future research in this field. Firstly, it is advisable that future studies report more information regarding the definition of LBP. Issues relating to the exact area of pain, the frequency of episodes, their intensity, and the duration need to be specified. Secondly, there is a need to improve the methodological quality of studies in order to avoid threats against the representativeness of the samples and the internal validity of the studies. Finally, studies should report prevalence rates of LBP disaggregated by age and sex.
In conclusion, the most recent studies seem to show higher prevalence rates than the oldest ones, and studies with a better methodology tend to show higher lifetime prevalence rates than studies that are methodologically poor.