Disentangling the effects of current age, onset age, and disease duration: parent and child attitudes toward diabetes as an exemplar.

OBJECTIVE: To develop a methodology for use with cross-sectional data to disentangle the effects of current age, disease onset age, and disease duration in chronically ill children.
METHODS: We used a questionnaire data set from a large cross-sectional sample of mothers and children with Type 1 diabetes. The interdependence of current age, onset age, and disease duration precluded use of all three in the same regression model. Consequently, pairs of models were run, looking for a pattern in the results.
RESULTS: The approach successfully disentangled the differential effects of the child's current age, disease onset age, and disease duration. Child current age predicted child attitudes about diabetes management rules, child sick-role identification, and maternal attitudes toward medical staff. Onset age predicted child-perceived family disruption and mothers' confidence in detecting a hypoglycemic reaction. Disease duration predicted maternal religious beliefs about diabetes and maternal attitudes toward medical staff.
CONCLUSIONS: This study illustrates a methodology for disentangling the effects of child current age, disease onset age, and disease duration in cross-sectional data that may be useful for any childhood chronically ill population that varies in child onset age.