164 Chapter 5 Table 3. Spearman correlation coefficients for delta leptin values and delta fatigue, sleep, hunger score and fat mass. Delta Leptin SDS 95%-Confidence Interval n rs Lower bound Upper bound Delta fat mass (kg) 78 -0.18 -0.38 0.05 Delta BMI 83 0.13 -0.09 0.33 Delta Hunger score 71 Average 0.18 -0.06 0.40 Most 0.05 -0.19 0.28 Least 0.08 -0.16 0.31 Fasting 0.04 -0.20 0.27 Delta Fatigue SDS 73 0.04 -0.20 0.26 Delta Sleep SDSC Total score 82 -0.14 -0.35 0.08 Abbreviations: SDS: standardized deviation score, SDSC: sleep disturbance scale for children. Potential influencing factors for high leptin To explore which patient and treatment factors may contribute to a high leptin level (SDS>1.5) on T1, we estimated univariable logistic regression models (Table 4). An older age increased the odds of a high leptin level at T1 with 1.51 per year (95%-CI 1.28 to 1.77). A higher fat mass at T1 increased the odds with 1.19 per kg (95%-CI 1.07 to 1.33). Earlier weeks of maintenance treatment (i.e. how far along a patient was in his/her treatment) revealed higher leptin values: every week further in maintenance gave a 0.96 lower odds (95%-CI 0.92 to 0.99) of high leptin. Fatigue, sleep problems and hunger scores at T1 were not associated with a high leptin at T1. Linear regression models were estimated to study the effect of possible explanatory variables on the change in leptin SDS during a dexamethasone course, with a correction for T1 leptin values (Table 5). Age at measurement was associated with the change in leptin: one year increase, increased delta leptin SDS with 0.08 (95%-CI 0.02 to 0.15). Week of maintenance was also negatively associated with delta leptin values: -0.02 (95%-CI -0.04 to -0.01). Whether a child received asparaginase during the study was also associated with the increase in leptin: if a child received asparaginase, delta leptin SDS was 1.09 higher (95%-CI 0.39 to 1.79). Of note, only 11 children received asparaginase during the study measurements.
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