The link between aerobic fitness and physical activity in children has been studied in a number of earlier studies and the results have generally shown weak to moderate correlations. This overall finding has been widely questioned partly because of the difficulty in obtaining valid estimates of physical activity. This study investigated the cross-sectional and longitudinal relationship between aerobic fitness and physical activity in a representative sample of 9 and 15-year-old children (n = 1260 cross-sectional, n = 153 longitudinal). The specific goal was to improve past studies using an objective method of activity assessment and taking into account a number of major sources of error. Data came from the Danish part of the European youth heart study, 1997-2003. The cross-sectional results generally showed a weak to moderate association between aerobic fitness and physical activity with standardized regression coefficients ranging from 0.14 to 0.33. The longitudinal results revealed a tendency towards an interaction effect of baseline physical activity on the relationship between changes in physical activity and aerobic fitness. Moderate to moderately strong regression effect sizes were observed in the lower quadrant of baseline physical activity compared to weak effect sizes in the remaining quadrants. In conclusion, the present study confirms earlier findings of a weak to moderate association between aerobic fitness and physical activity in total population of children. However, the study also indicates that inactive children can achieve notable increase in aerobic fitness by increasing their habitual physical activity level. A potential physiological explanation for these results is highlighted.
Vertebral endplate signal changes (VESC) are more common among patients with low back pain (LBP) and/or sciatica than in people who are not seeking care for back pain. The distribution and characteristics of VESC have been described in people from clinical and non-clinical populations. However, while the clinical course of VESC has been studied in patients, the natural course in the general population has not been reported. The objectives of this prospective observational study were to describe: 1) the distribution and characteristics of VESC in the lumbar spine, 2) its association with disc degeneration, and 3) its natural course from 40 to 44 years of age.
Three-hundred-and-forty-four individuals (161 men and 183 women) sampled from the Danish general population had MRI at the age of 40 and again at the age of 44. The following MRI findings were evaluated using standardised evaluation protocols: type, location, and size of VESC, disc signal, and disc height. Characteristics and distribution of VESC were analysed by frequency tables. The association between VESC and disc degeneration was analysed by logistic regression analysis. The change in type and size of VESC was analysed by cross-tabulations of variables obtained at age 40 and 44 and tested using McNemar's test of symmetry.
Two-thirds (67%) of VESC found in this study were located in the lower part of the spine (L4-S1). VESC located at disc levels L1-L3 were generally small and located only in the anterior part of the vertebra, whereas those located at disc levels L4-S1 were more likely to extend further into the vertebra and along the endplate. Moreover, the more the VESC extended into the vertebra, the more likely it was that the adjacent disc was degenerated. The prevalence of endplate levels with VESC increased significantly from 6% to 9% from age 40 to 44. Again, VESC that was only observed in the endplate was more likely to come and go over the four-year period compared with those which extended further into the vertebra, where it generally persisted.
The prevalence of VESC increased significantly over the four-year period. Furthermore, the results from this study indicate that the distribution of VESC, its association with disc degeneration and its natural course, is dependent on the size of the signal changes.
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Understanding a change score is indispensable for interpretation of results from clinical studies. One way of determining the relevance of change scores is through the use of transition questions that assesses patients' retrospective perception of treatment effect. Unfortunately, results from studies using transition questions are difficult to compare since wording of questions and definitions of important improvements vary between studies. The objectives of this study were to determine the consequence of using different transition questions on pain and disability measures and make proposals for a standardised use of such questions. Two hundred and thirty-three patients with low back pain and/or leg pain were recruited. Participants were followed over an 8-week period and randomised to two groups receiving a 7- (TQ1) and 15-point (TQ2) transition question, respectively, in addition to a numeric rating scale evaluating the importance of the perceived change. Four external criteria were generated using both stringent and less stringent standards to dichotomise patients. Discrimination was determined using area under the receiver operating characteristic curve (ROC(auc)) and responsiveness using standardised response mean (SRM). Results demonstrated small variations in ROC(auc) across the external criteria for all outcome measures. 7% more patients were classified as improved in the group receiving the 15-point TQ compared to the 7-point TQ (stringent standard). SRMs were higher for the retrospective TQs in primary sector patients compared to the serial measures with no difference between TQ1 and TQ2. On the basis of our findings we have outlined a proposal for a standardised use of transition questions.
In studies evaluating the efficacy of clinical interventions, it is of paramount importance that the functional outcome measures are responsive to clinically relevant change. Knowledge thereof is in fact essential for the choice of instrument in clinical trials and for clinical decision-making. This article endeavours to investigate the sensitivity, specificity and clinically significant improvement (responsiveness) of the Danish version of the Oswestry disability index (ODI) in two back pain populations. Two hundred and thirty three patients with low back pain (LBP) and/or leg pain completed a questionnaire booklet at baseline and 8 weeks follow-up. Half of the patients were seen in the primary (PrS) and half in the secondary sectors (SeS) of the Danish Health Care System. The booklet contained the Danish version of the ODI, along with the Roland Morris Questionnaire, the LBP Rating Scale, the SF36 (physical function and bodily pain scales) and a global pain rating. At follow-up, a 7-point transition question (TQ) of patient perceived change and a numeric rating scale relating to the importance of the change were included. Responsiveness was operationalised using three strategies: change scores, standardised response means (SRM) and receiver operating characteristic (ROC) analyses. All methods revealed acceptable responsiveness of the ODI in the two patient populations which was comparable to the external instruments. SRM of the ODI change scores at 2 months follow-up was 1.0 for PrS patients and 0.3 for SeS (raw and percentage). A minimum clinically important change (MCID) from baseline score was established at 9 points (71%) for PrS patients and 8 points (27%) for SeS patients using ROC analyses. This was dependable on the baseline entry score with the MCID increasing with 5 points for every 10 points increase in the baseline score. We conclude that the Danish version of the ODI has comparable responsiveness to other commonly used functional status measures and is appropriate for use in low back pain patients receiving conservative care in both the primary and secondary sector.
Cross-sectional cohort study of a general population.
To investigate "abnormal" lumbar spine magnetic resonance imaging (MRI) findings, and their prevalence and associations with low back pain (LBP).
The clinical relevance of various "abnormal" findings in the lumbar spine is unclear. Distinguishing between inevitable age-related findings and degenerative findings with deleterious consequences is a challenge.
Lumbar spine MRI was obtained in 412, 40-year-old individuals. Predefined "abnormal" MRI findings were interpreted without any knowledge of patient symptoms. Associations between MRI abnormalities and LBP were calculated using odds ratios. The "overall picture" of each MRI finding was established on the basis of the frequencies, diagnostic values, and the strength and consistency of associations.
Most "abnormal" MRI findings were found at the lowest lumbar levels. Irregular nucleus shape and reduced disc height were common (>50% of individuals). Relatively common (25% to 50%) were hypointense disc signal, anular tears, high intensity zones, disc protrusions, endplate changes, zygapophyseal joint degeneration, asymmetry, and foraminal stenosis. Nerve root compromise, Modic changes, central spinal stenosis, and anterolisthesis/retrolisthesis were rare (4). Significantly positive associations with all LBP variables were seen for hypointense disc signals, reduced disc height, and Modic changes. All disc "abnormalities" except protrusion were moderately associated with LBP during the past year.
Most degenerative disc "abnormalities" were moderately associated with LBP. The strongest associations were noted for Modic changes and anterolisthesis. Further studies are needed to define clinical relevance.
Very few studies have reported on the effect of admission tests on medical school dropout. The main aim of this study was to evaluate the predictive validity of non-grade-based admission testing versus grade-based admission relative to subsequent dropout.
This prospective cohort study followed six cohorts of medical students admitted to the medical school at the University of Southern Denmark during 2002-2007 (n=1544). Half of the students were admitted based on their prior achievement of highest grades (Strategy 1) and the other half took a composite non-grade-based admission test (Strategy 2). Educational as well as social predictor variables (doctor-parent, origin, parenthood, parents living together, parent on benefit, university-educated parents) were also examined. The outcome of interest was students' dropout status at 2 years after admission. Multivariate logistic regression analysis was used to model dropout.
Strategy 2 (admission test) students had a lower relative risk for dropping out of medical school within 2 years of admission (odds ratio 0.56, 95% confidence interval 0.39-0.80). Only the admission strategy, the type of qualifying examination and the priority given to the programme on the national application forms contributed significantly to the dropout model. Social variables did not predict dropout and neither did Strategy 2 admission test scores.
Selection by admission testing appeared to have an independent, protective effect on dropout in this setting.
To identify correlates of objectively measured moderate and vigorous physical activity (MVPA) in children during preschool attendance.
This cross-sectional study included data from 426 apparently healthy Danish children (49.5% boys), 5 to 6 years of age enrolled in 42 randomly selected preschools. The percentage of time spent in MVPA (= 574 counts/15 second) during preschool attendance was measured using ActiGraph accelerometers over 4.3 preschool days in May and June in 2009. Thirty-seven potential correlates across the child, preschool staff, and preschool environment domains were tested for associations with MVPA.
The final multivariate model identified 9 significant correlates of MVPA. Preterm birth, vegetation on the playground, and rainy days were negatively associated with MVPA, whereas child motor coordination, location of preschool building on the playground, gender (boys), percentage afternoon hours, and size of indoor area per child were positively associated with MVPA. The direction of the significant association with the parental mean education level was unclear.
We identified a number of new modifiable correlates of MVPA during preschool attendance. The positive association with size of indoor area per child and location of the preschool building on the playground seem important correlates to be targeted in future studies.
Vertebral endplate signal changes (VESC), also known as Modic changes, have been reported to be associated with low back pain (LBP). However, little is known about predisposing factors for the development of new VESC. The aim of this study was to investigate the predictive value of lifestyle factors and disc-related magnetic resonance imaging (MRI) findings in relation to the development of new VESC. This prospective observational study included 344 people from the Danish general population who had an MRI and completed LBP questionnaires at the age of 40 and again at 44 years. Potential predictors of new VESC were female gender, disc-related MRI findings (disc degeneration, disc bulges, disc herniation, and other endplate changes) and lifestyle factors [high physical work or leisure activity, high body mass index (BMI), and heavy smoking]. Bivariate and multivariate logistic regressions were used to identify predictors of new VESC. New VESC at the age of 44 appeared in 67 of the 344. The majority (84%) of these new signal changes were type 1 VESC and almost half (45%) were only in the endplate and did not extend into the vertebral body. In the multivariate analysis, lumbar disc levels with disc degeneration, bulges or herniations at 40 were the only predictors of new VESC at age 44. Therefore, the development of new VESC at the age of 44 appears to be based on the status and dynamics of the disc, rather than being the result of gender or lifestyle factors such as smoking and physical load.
It is generally acknowledged that back pain (BP) is a common condition already in childhood. However, the development until early adulthood is not well understood and, in particular, not the individual tracking pattern. The objectives of this paper are to show the prevalence estimates of BP, low back pain (LBP), mid back pain (MBP), neck pain (NP), and care-seeking because of BP at three different ages (9, 13 and 15 years) and how the BP reporting tracks over these age groups over three consecutive surveys.
A longitudinal cohort study was carried out from the years of 1997 till 2005, collecting interview data from children who were sampled to be representative of Danish schoolchildren. BP was defined overall and specifically in the three spinal regions as having reported pain within the past month. The prevalence estimates and the various patterns of BP reporting over time are presented as percentages.
Of the 771 children sampled, 62%, 57%, and 58% participated in the three back surveys and 34% participated in all three. The prevalence estimates for children at the ages of 9, 13, and 15, respectively, were for BP 33%, 28%, and 48%; for LBP 4%, 22%, and 36%; for MBP 20%, 13%, and 35%; and for NP 10%, 7%, and 15%. Seeking care for BP increased from 6% and 8% at the two youngest ages to 34% at the oldest. Only 7% of the children who participated in all three surveys reported BP each time and 30% of these always reported no pain. The patterns of development differed for the three spinal regions and between genders. Status at the previous survey predicted status at the next survey, so that those who had pain before were more likely to report pain again and vice versa. This was most pronounced for care-seeking.
It was confirmed that BP starts early in life, but the patterns of onset and development over time vary for different parts of the spine and between genders. Because of these differences, it is recommended to report on BP in youngsters separately for the three spinal regions, and to differentiate in the analyses between the genders and age groups. Although only a small minority reported BP at two or all three surveys, tracking of BP (particularly NP) and care seeking was noted from one survey to the other. On the positive side, individuals without BP at a previous survey were likely to remain pain free at the subsequent survey.