This is the first study to demonstrate the feasibility and utility of actigraphy-based physical activity monitoring as an objective indicator of physical functioning in adolescents with JPFS. Adolescents wore hip-mounted actigraphs for one week of continuous activity monitoring, and adolescents and parents provided information about the adolescents’ pain intensity, psychological symptoms and perceived disability using validated, self-report measures. Although hip-mounted actigraphs are somewhat less convenient than ankle or wrist placements, they provide an accurate indication of whole body movement. It was not uncommon for adolescents to miss one or two days of wearing the monitor for the week, but we were able to obtain at least 5 days of complete data for all participants.
Results showed that adolescents with JPFS spent relatively little time in moderate or vigorous physical activity despite receiving the usual medical recommendations at all study sites for increased aerobic exercise. In fact, only 23% of adolescents met rheumatology recommendations for 30 minutes of moderate to vigorous physical activity and only one met national guidelines of 60 minutes of moderate to vigorous physical activity daily 4
. These results were not unexpected, given the decreased activity levels found in children and adolescents with chronic pain 25
. National statistics also show that physical activity levels in adolescents in general are quite low 3
. The Youth Risk Behavior Surveillance System reported that only 34.7% of adolescents met recommended levels of physical activity 5
and 22.6% of youth did not engage in any type of vigorous physical activity 2
. Nevertheless, the low overall levels of activity in JPFS patients are concerning because increased exercise is generally viewed as a key component for improved pain management in JPFS.
Higher pain intensity ratings were not significantly associated with lower levels of vigorous activity or activity counts in the overall sample, suggesting that pain by itself may not be directly related to whether or not adolescents with JPFS are able to engage in higher activity levels. This is contrary to what most adolescents with JPFS and parents typically report, as pain is routinely cited as the primary reason for inability to exercise. This is also different from the results of the Long et al. pediatric study 25
which found that adolescent report of functional impairment, depression and pain were significantly (inversely) associated with activity levels. The results of our study did not replicate these findings, possibly due to differences in actigraphy methodology, or the characteristics of the pain population - which included only adolescents with JPFS in this study. Aside from chronic pain, JPFS patients have a number of associated symptoms such as fatigue, sleep difficulties etc. which may affect activity levels as well. In the current study, it appeared that parents were more likely than adolescents to recognize that psychological factors, such as depressive symptoms, may affect their adolescent’s activity. According to parent reports, higher levels of depressive symptoms and functional disability were significantly correlated with lower engagement in vigorous activity and fewer activity counts whereas correlations between adolescents’ responses on self-report measures and objective measurement of physical activity were very low. The fact that there was essentially no relationship between adolescents’ perception of their functional disability and actual levels of physical activity was notable. Together, these findings suggest that activity monitoring provides a unique source of information which has the potential to be very helpful in educating and monitoring adolescents’ engagement in physical activity. This finding also underscores the importance of multi-method approaches to measurement of physical impairment in adolescents with chronic pain.
There were a small number of adolescents with JPFS who maintained high levels of vigorous activity, which is consistent with our clinical knowledge of this population. Clinicians often report that a subset of patients with JPFS make a concerted effort to remain involved in sports or other vigorous activities despite their symptoms. This group is particularly interesting from the point of view of understanding how some adolescents adaptively cope with their condition and show relatively little physical impairment. Significant differences emerged when we looked more closely at differences between adolescents who were in the most active and least active quartiles of vigorous activity. After controlling for the known effects of age, the subset of the sample that included the most active adolescents reported lower levels of pain, and their parents reported that they had significantly lower depressive symptoms and disability than the least active group. It should be noted that causal connections cannot be made in this cross sectional study. Therefore, higher pain levels in the least active group may be related to their decreased activity or vice versa. Also, the results of this subgroup analysis may not be generalizable to all adolescents with JPFS. Nevertheless, it is clear that patients with JPFS who were highly active were qualitatively different and appeared to have lower levels of physical and psychological impairment.
In contrast to the study in adults with fibromyalgia, there were no significant differences in vigorous activity among adolescents who were diagnosed with a depressive disorder and those who were not. This might be due to the differences in the manifestation of clinical depression in adults (who may have more vegetative symptoms) compared to children, so that a DSM-IV diagnosis of depression in adolescents may not have the same implications for their activity levels. On the other hand, parent-report of the severity of the adolescents’ depressive symptoms appeared to be a more sensitive indicator because it was shown to be significantly associated with activity levels. The presence of anxiety disorders did not appear to have any significant bearing on physical activity.
The findings of this study should be interpreted in light of several limitations. Because this is the first study to use actigraphy in the JPFS population, there are no established norms or comparable studies using the same methodology in other pediatric populations. Hence, replication of the findings is needed to confirm the results of this study. Additionally, there was no control group in this study vigorous physical activity levels of adolescents with JPFS could not be compared to “typical” adolescents. We suspect that the wider availability of newer technologies such as actigraphy will make it more likely that such objective and ecologically valid (real-world setting) measures will be increasingly integrated into chronic pain research. A second limitation is that the cross-sectional nature of the study precludes making any causal connections beyond demonstrating that adolescents who (objectively) remain highly active tend to have fewer depressive symptoms and are seen as less disabled by their parents. Third, we examined activity levels during daytime hours, which may have overlapped with time spent sleeping for those adolescents who napped during the day. Additionally, we did not measure fear or avoidance of activity related to anticipatory anxiety which may partially explain the lack of relationship between adolescents’ reported pain and decreased vigorous physical activity. Finally, there appear to be sex differences in physical activity but these could not be sufficiently examined in this study because JPFS is prevalent mainly in adolescent girls, and more studies with pediatric pain populations are needed to explore how sex differences in physical activity might influence clinical outcomes.
Future studies are needed to investigate whether exercise-based programs and/or cognitive-behavioral approaches that include recommendations for greater physical activity levels have an effect on objectively measured physical activity. It would also be beneficial to explore whether increased physical activity levels might be related to better prognosis and long-term outcomes in those diagnosed with JPFS. Objective information regarding an individual’s engagement in physical activity may be eventually used as an effective tool to increase the effectiveness of treatment approaches to reduce disability and enhance quality of life in adolescent JPFS patients.