The CAMP trial has provided a large-scale framework for examining asthma medication treatment outcomes pertaining to children with mild and moderate asthma. The results presented provide new insight for researchers into variables associated with moderate improvement and decline in quality of life outcomes. Within the current analyses, a focus on change that has occurred in quality of life between the 12-month and 36-month follow-up CAMP visits has been examined, with results indicating that change in children's self-reported quality of life are associated with several specific disease and behavioral characteristics. Moreover, change that occurs in a child's Total Score and Emotional Functioning domain of quality of life over a 24-month period was likely to be associated with specific aspects of child psychological functioning when moderate improvements in quality of life occur. Striking in these findings was how medication treatment arm did not contribute to changes (improvement or decline) in child or parent quality of life during the interval assessed. Rather, the use of steroid therapy during the preceding 4 months was the single determinant of moderate improvement in child-reported participation in the Physical Activities domain of quality of life. In contrast, a combination of poor lung function, reports of asthma interfering with the child's life, and specific child psychological functioning were the factors most strongly associated with moderate decline in child-reported quality of life total score.
Child report of subclinical depressive symptomatology was observed as an associated feature of both improvement and decline in quality of life. Child acknowledgement of depressive symptoms in this study were found to be remarkably low (overall mean raw score = 4.7, SD 4.9) suggesting that children participating in the CAMP study were reporting subclinical depressive symptoms compared to the normative population for the CDI. Our findings may be interpreted as suggesting that reports of subclinical scores on the CDI can be associated with both improvement and decline in quality of life. It is the other features associated with subclinical depressed affect that determine the valence of the moderate change in quality of life. While this line of reasoning may be perceived as controversial, there is emerging evidence suggesting that children with asthma may have increased subclinical levels of depressed affect that can be associated with physiological functioning. Von Leupoldt, Ehnes, and Dahme (2006)
have demonstrated that individuals with asthma experience change in lung function in response to both positive and negative emotional stimuli. It may be that children with asthma develop subclinical affective symptoms in response to the challenges of managing their disease. Other lines of research indicate that children with asthma who exhibit higher amounts of anxiety have increased symptom perception skills (Chen, Hermann, Rodgers, Oliver-Welker, & Strunk, 2006
), a finding that could be considered consistent with the current results.
Two major conclusions can be drawn from the present findings: 1) subclinical levels of depressed affect, as reported by children, can be associated with improvement in quality of life when there is no co-occurring change in lung function; and 2) when subclinical levels of depressed affect are observed in association with asthma treatment changes and/or changes in lung function, there is likely to be a decline in child-reported quality of life. Unlike studies that have suggested a decline in lung function when children experience some negative emotion (e.g., Miller & Wood, 1997
; Neild & Cameron, 1985
; Ritz, Claussen, & Dahme, 2001
), our findings suggest a more nuanced psychological picture where subclinical levels of depressed affect (as represented in this study by symptoms on the CDI) can be a useful tool for helping trigger intervention that lead to improved control of asthma and thus improvement in quality of life.
Parent reports of their quality of life were obtained within the clinic visit when child-reported quality of life assessments were obtained. Using a total quality of life change score during the 24-month interval, greater report of perception of disease burden (as represented by the IOF score) was associated with improvement in parent quality of life. This finding must be understood within the context of family factors, and specifically the report of the extent to which rules and procedures (represented by the FES Control scale) are used to guide family life. When parents report improvement in their quality of life, this is associated with increased awareness of burden of disease and normal levels of parental control. It may be inferred that the awareness of illness burden results in increased parent commitment to developing rules and procedures for managing and helping the child manage their asthma. Again, the data from the participants in the CAMP ancillary study reveal the influences of both family characteristics and perception of illness burden as contributors to the parent perception of improvement in quality of life.
A striking difference was observed when parents report a moderate decline in quality of life. School days missed combined with higher levels of family member independence and a restricted range of social supports each contribute to decline over the 24-month interval. Thus when the parent reports a decline in quality of life, this is very likely to be associated with an increased expectation of independence (represented by the FES Independence scale) for the child with asthma, which occurs in combination with the child missing school and lower levels of social support. Within the context of an asthma clinical setting, finding a change in parent quality of life total score of at least one point would potentially suggest targets for psychosocial intervention, such as helping the parent to make modifications in the family support system and the expectations for child independence.
The results from this study contribute to the understanding of change in quality of life scores for children with asthma. Perhaps the most significant of these contributions is that child and parent reports of quality of life moderate improvement and decline are affected by different sets of features. Previous reports on predictors of child and parent quality of life have suggested that child-reported anxiety is the predominant feature influencing quality of life (Annett, Bender, Lapidus, DuHamel & Lincoln, 2001
), and that parent perception of illness burden significantly influences their report of the quality of life of their child with asthma (Annett, Bender, DuHamel & Lapidus, 2003
). Results in this current investigation extend the previous findings by demonstrating that moderate change in quality of life over a 24-month interval is influenced by distinct features, depending upon whether the child or the parent is the source of the observation.
There are several features of the CAMP study that merit recognition in these findings. First, the interval of examination within this study is extensive. No studies to date have examined quality of life change over such an lengthy period of time for children involved in a clinical trial where changes in disease characteristics and treatment were thoroughly mapped (see CAMP, 2000
). Additionally, participants in this study were engaged in an intervention aimed at assessing differences in asthma medication treatments. As such, these participants were receiving a high level of surveillance of their asthma symptoms and active intervention for asthma exacerbations. The CAMP study participations have previously been described in significant detail (CAMP, 1999
) and appear to represent the preponderance of asthma severity in childhood (i.e., children with mild to moderate asthma). There are several limitations to the study results, including that study participants did not include children with more severe asthma. Additionally, quality of life was measured while asthma medication treatments were occurring, rather than being assessed before treatment began and again during treatment. Yet, one of the unique findings from this study was how 12 to 36-month change in quality of life was not impacted by CAMP treatment condition, raising the question of under what conditions treatment condition may impact quality of life for children with asthma and their parents. However, the unique examination of improvement and decline during medication treatment provides a contribution to the understanding of variables contributing to quality of life changes that occur for this subset of CAMP participants.
In summary, moderate improvement and decline in quality of life do occur when children with mild and moderate asthma participate in a controlled clinical research treatment program. Furthermore, these changes can be observed in reports from children about their quality of life and from the reports from parents about parent quality of life. Depending upon whether the child or the parent is the focus of the quality of life endpoint, different asthma disease features and psychological characteristics were observed to predict improvement or decline. This study has highlighted how subjective, intra-individual change of one point in a quality of life questionnaire is associated with measures of both psychological functioning and disease features. These findings propose a broadening of the procedures for assessing moderate improvement and decline in subjective reports of disease-related functioning to include measures of psychosocial parameters as well as disease characteristics.