The primary goal of the study was to determine whether stressful life events were associated with metabolic control for adolescents with diabetes. Using growth curve modeling with a fairly large sample of adolescents, we found that stressful life events were associated with poor metabolic control concurrently and predicted declines in metabolic control over time. In the cross-sectional analyses, this relation only appeared among older teens. Because we enrolled 10 to 14-year-olds in the study and followed them for five years, we were able to examine the relation of stressful life events to metabolic control for a larger age range—10 through 18 years of age. Thus, one reason that a relation between stress and metabolic control has not been found consistently in previous research is that younger adolescents’ metabolic control may not be affected by stressful life events. There are several reasons that stressful life events may play a larger role in the health of older than younger adolescents. First, older adolescents have greater knowledge, increased complexity of thought, and are able to understand the consequences of events more fully (Holmbeck et al., 2006
). Second, younger adolescents may be less affected by stressful life events because parents intervene on their behalf. Parents may exert a stronger effect on the behavior of younger teens, buffering any adverse effect of life stressors. Our cross-sectional finding for meter readings supports this possibility. For older children, more stressful life events were associated with fewer meter readings. But for younger children, more stressful life events were associated with more frequent
meter readings. It may be that parents of younger children are sensitive to the stress in their child’s environment, aware of its potential impact on metabolic control, and intervene by ensuring that the behavior—testing blood sugar—is enacted. Because previous studies have often employed wide age ranges of adolescents with small sample sizes, they have not been able to test whether the relation of stressful life events to metabolic control held for only a portion of the sample. It also is the case that age was related to more stressful life events; thus, stronger relations may have appeared among older adolescents because the frequency of stressful life events increased in this age group.
A second goal of the study was to determine whether we could explain the relation of stressful life events to poor metabolic control. We noted that there are two pathways by which stress is thought to influence metabolic control: (1) the neuroendocrine system and (2) behavior. Although we did not have direct measures of neuroendocrine function, we did assess psychological distress which is thought to be influenced by neuroendocrine hormones. Stressful events predicted all three indicators of psychological distress in cross-sectional and longitudinal analyses, but there was no evidence that psychological distress mediated the relation of stressful life events to metabolic control. Because we did not have direct measures of neuroendocrine function, we cannot rule out that pathway in the present study. However, there was some evidence that behavior mediated this relation. Stressful life events predicted both the self-care behavior index and the average number of meter readings taken per day in both cross-sectional and longitudinal analyses. The life events by age interaction was reduced to nonsignificance when meter readings was statistically controlled while the effect for meter readings remained significant. These findings are consistent with the idea that stressful life events detract from self-care behavior, including blood glucose testing, which then has adverse effects on metabolic control. This model appears to hold only for older adolescents. In addition, this mediational pathway was not significant in the longitudinal analyses. Thus, more work is certainly needed to elucidate the precise mechanism by which stress may adversely affect metabolic control among adolescents.
Although the focus of the study was on metabolic control, it also is important to note that stressful life events were associated with indicators of psychological distress, confirming previous research that has demonstrated such a relation (e.g., Byrne et al., 2007
). We anticipated that these relations would be stronger for girls than boys. There was only modest evidence that girls were more responsive to stress than boys. In cross-sectional analyses, stressful life events were more strongly associated with depressive symptoms for girls than boys. Importantly, there was no interaction between stressful life events and sex on either measure of self care or metabolic control. Thus, although stressful life events might pose a more significant source of distress for girls, stressful life events did not seem to have any stronger effects on girls’ behavior or metabolic control in this study.
These results have implications for clinicians’ treatment of children and adolescents with type 1 diabetes. In discussions with adolescents, clinicians should probe for information about potential stressors. Alternatively, clinician offices could easily administer a brief life events checklist prior to the appointment and use that instrument as a screen or vehicle for discussion. When there has been an increase in stressful life events, it would be helpful for clinicians, family, and the adolescent to understand the potential impact on behavior.
Before concluding, we must acknowledge several limitations of this study. First, the sample of children was quite homogeneous with respect to race, limiting the generalizabililty of the findings. Future research would benefit by examining stressful life events in a more diverse group both racially and economically. Second, our assessments were spaced quite far apart—once each year. Although a strength of the study is its longitudinal design, future research would benefit from studies that capture the more proximal effects of stress on blood glucose. Daily diary or ecological momentary methods are designs that could help to discern the relation of stress to blood glucose. Finally, we focused on a global checklist of stressful life events. Future research would benefit from examining specific dimensions or categories of stressors.
In sum, following a fairly large sample of adolescents for five years and spanning a large age range, we were able to demonstrate that stressful life events are associated with poor metabolic control, that this relation holds for the older end of the adolescent spectrum, and that stressful life events predicted a deterioration in metabolic control over time. We also showed that self-care behavior may be a primary contributor to this relation.