In this study we compared participation in life activities and perceived QoL between boys with DMD and an age-matched population of unaffected boys. The results showed that participation in physical activities was significantly lower in boys with DMD than unaffected controls, although other participation measures were much the same as healthy boys. Furthermore, perceived QoL was markedly diminished in children with DMD relative to unaffected controls. Another objective of this study was to compare younger boys to older boys in both the DMD and unaffected cohorts to explore both within group and between group differences in participation and QoL. For within group differences, we found that the amount of time boys with DMD engage in an activity (frequency), as well as participation in social activities, declined for our older cohort but there was no decline in participation observed for our older unaffected boys. No differences in perceived QoL were observed between the younger and older boys with DMD or the unaffected boys. Significant between age group differences were observed among the boys with DMD and the unaffected controls. Comparisons between our younger boys with DMD and our younger unaffected boys showed lower scores in diversity of activities they participate in, as well as participation in physical activities. Quality of life scores were lower in the physical subscale as well as the overall total composite score. For our older boys with DMD, lower scores were reported in both physical and social participation, as well as quality of life subscales of physical, social and total composite scores compared to our older unaffected boys. No differences were observed in the PedsQLTM subscales of emotional or school related QoL for our older boys. Finally, no correlations were observed between reports of participation and QoL in these two groups.
Our study is one of the first to explore self-report of participation in activities in a population of boys with DMD. The results demonstrated that, overall, the boys with DMD chose diverse activities in which to participate and that they were involved in their chosen activities as frequently as healthy boys. However, the activities of choice for boys with DMD were less physical in nature than unaffected boys their age. It certainly comes as no surprise that children with muscular weakness are less likely to participate in physical activities, especially as they age [46, 47]. Interestingly, physical activity for healthy boys has been reported to decline during later childhood or adolescence stages [48, 49], although we did not observe a decline in our unaffected group of boys. In contrast, this age-related decline in physical activities for unaffected boys does not appear to be due to the bodily demands of the activity [49, 50]. Moreover, physical activity participation is typically high for younger unaffected boys , but was significantly lower in our younger boys with DMD.
In boys with DMD, participation in social activities, such as visiting friends, going to parties or going to the movies was significantly lower after the age of 10 years. This is often the age when boys with DMD experience a decrease in motor abilities, such as ambulation [5, 46] and may, therefore, have less opportunity for community-based social engagement. It’s important to note the connection between physical abilities and social engagement. Poor motor skills have been associated with peer relationship difficulties, lower peer regard and greater likelihood of suffering from withdrawal . Actively engaging in physical activities, such as team sports or playing with others on the playground, helps children form peer relationships and experience a sense of self-worth and belonging to a group [30, 40, 51, 52]. Unfortunately, little is known about the social engagement of children with DMD. Although parents more often report prolonging ambulation as the most important factor in dealing with DMD [39, 53], the resulting emotional challenges of DMD and the increasing social needs of boys as they age is also of great concern [39, 54].
Our study also used self-report measures to determine the perceived QoL of the boys with DMD relative to unaffected controls. The boys with DMD reported lower physical, social and school-related scores, resulting in significantly lower total composite QoL scores. However, there was no effect of the disease in the emotional area of QoL, even as the boys aged. The differences in these responses may be due to the types of questions used in the PedsQLTM assessment. The questions addressed in the physical, social, and school-related areas are based on difficulties in actual performance, such as physical activities, making friends, or missing school due to medical/physician appointments. On the other hand, the emotional subscale of the PedsQLTM consists of questions about feelings of sadness, anger, and fear. These may be emotions that are evident in most children to some degree and may not necessarily be exaggerated by the disease. It is interesting to note that although QoL scores for boys with DMD were significantly lower than for unaffected boys, these scores did not notably decrease within the cohort of children with DMD when the disease has typically progressed. Other researchers have also reported no changes in QoL related to disease progression [11, 12, 43, 55]. In a longitudinal study, Simon and colleagues (2010) used the Life Satisfaction Index for Adolescents, which they determined to be a more effective instrument for boys with DMD based on its limited focus on physical abilities. No comparisons were made with unaffected boys, but the cohort of 95 boys with DMD did not show a significant decrease and no loss of QoL was observed among the boys most affected by the progression of the disease . Abresch et al. [56, 57] determined that physical functioning and level of disability alone did not alter overall QoL, a finding that was also reported by Kohler et al.  using the Short-Form 36 of the medical outcome questionnaire. Finally, based on PedsQLTM scores established and validated in a variety of patient populations [37, 58], the overall scores for our cohort of boys with DMD were lower than scores from children with other major chronic health issues.
In our study, we did not find a relationship between CAPE participation scores and PedsQLTM quality of life scores for unaffected boys or boys with DMD, although relationships between QoL and specific clinical measures that are typically assessed in boys with DMD have been observed. Bray et al.  found relationships between age, steroid use, physical functioning and QoL in DMD. McDonald et al.  utilized parent-proxy report and found direct relationships between the physical domains of QoL, age, and such clinical assessments as supine to stand, walk/run 10 meters and walk up 4 stairs. Findings from other studies in DMD support the thought that meaningful and developmentally important life activities, such as playing with and actively engaging with friends, may be related to QoL [11, 59]. It is difficult to explain these varying results and why we did not find a correlation between participation and QoL. Although our sample size was small, it would also appear that QoL is complex and more global in nature than the straightforward and explicit report of actual participation. As Colver theorized, QoL cannot be measured directly, but only captured through a variety of questions that seek to place value on a particular variable . Therefore, QoL is a concept and is subjective , while participation is a real life experience and is objective [61–63]. Finally, our results may differ from some studies because we chose to use child report in lieu of parent proxy report to obtain a full understanding of the children’s perception of their QoL. Literature in this area shows that parents and children often differ in their agreement of the child’s QoL [13, 44, 64], but the larger issue appears to be whether a child is capable of self-report [65, 66]. We took the stance, as others have, that children can provide valuable information about their health and that quality of life is subjective and therefore should be a person’s individual view [33, 61, 65, 66].
We acknowledge there are a few limitations to our study. Although our population of boys with DMD is rare, our sample size may be considered relatively small, especially when broken into age groups. Moreover, as this was not a longitudinal study, comparing different age groups may not be giving us information about changes as the disease progresses. Lastly, although the PedsQLTM is a thoroughly developed generic measure that is brief, easy to understand, and captures information relevant to both children with a disease/illness and unaffected children, we acknowledge that the PedsQLTM domains are limited, are not designed to assess a full range of functioning and are not specific to children with a neuromuscular disorder.