Decline in IQ in Kids With T1DM From Diagnosis/Illness Onset
Decline in IQ in Kids With T1DM From Diagnosis/Illness Onset
Sample characteristics are presented in Table 1. At baseline, participants with type 1 diabetes did not differ significantly from HCs on age, sex, SES, or IQ scores. As previously reported, participants with type 1 diabetes had significantly lower VIQ and FSIQ scores than HCs at follow-up.
Mean changes in IQ scores for participants with type 1 diabetes, HCs, and each risk group are presented in Table 2. Those with type 1 diabetes showed significantly greater decline in VIQ and FSIQ over time than HCs (change in VIQ, F[1, 157] = 6.47, P = 0.01; change in FSIQ, F[1, 157] = 5.22, P = 0.02). There was no significant group difference in change in PIQ (F[1, 157] = 1.28; P = 0.3).
Regression analyses within the type 1 diabetes group are presented in Table 3. For any given baseline score, these models predict the IQ score at 12-year follow-up as predicted by each of the illness-related variables and covariates.
For each regression model, the overall model was significant. Baseline IQ and SES were always significantly associated with change in IQ, and length of follow-up was never significantly associated with change in IQ. A younger age at diabetes onset was significantly associated with negative change in PIQ and FSIQ. Based on the model with change in PIQ as the dependent variable, for any given PIQ score at baseline, the predicted follow-up PIQ score would be reduced by 2.36 points for each year earlier that diabetes onset occurred. Similarly, based on the model for change in FSIQ, for any given baseline FSIQ score, the predicted follow-up FSIQ score would be reduced by 0.97 points for each year earlier that diabetes onset occurred. A greater number of hypoglycemic seizures was significantly associated with negative change in VIQ. Thus, according to the model with VIQ as the dependent variable, for any given baseline VIQ score, VIQ at follow-up would be reduced by 1.19 points for each additional seizure. Metabolic control did not significantly predict change in IQ score. None of the interaction terms were significant.
Examining the Effect of Reduced HbA1c Measurements. Correlations between percentage of time HbA1c was ≥9.0% and change in VIQ, PIQ, and FSIQ conducted separately for those participants with ≥30 HbA1c values (n = 67; 70%) and those with <30 values were low for both groups (r <0.2) and not statistically significant. All regression analyses were repeated including only participants with ≥30 HbA1c values. Metabolic control still did not contribute significantly to change in VIQ, PIQ, and FSIQ (P > 0.9; P = 0.2; P = 0.4, respectively).
Potential Effect of BGL at the Time of Assessment. Mean BGL for participants with type 1 diabetes and each illness-related risk group (early or late onset, seizure history or no seizures, poor or good control) are reported in Table 2. The poor control group had significantly higher BGL prior to assessment at follow-up compared with the good control group (t[81.5] = 3.64; P < 0.001). There were no other significant group differences. Regression analyses were repeated covarying for BGL at baseline and then BGL at 12-year follow-up. Results were similar and are not reported here.
Exploration of Effect of DKA on Change in IQ. Thirty-one participants (32.6%) reported one or more episode of DKA (range 1–8; data missing on two participants). Means, SDs, and comparisons are presented in Table 4. Participants with one or more episode of DKA showed a greater loss in VIQ, PIQ, and FSIQ than participants without DKA episodes, but these were not statistically significant.
Results
Sample characteristics are presented in Table 1. At baseline, participants with type 1 diabetes did not differ significantly from HCs on age, sex, SES, or IQ scores. As previously reported, participants with type 1 diabetes had significantly lower VIQ and FSIQ scores than HCs at follow-up.
Type 1 Diabetes and HCs
Mean changes in IQ scores for participants with type 1 diabetes, HCs, and each risk group are presented in Table 2. Those with type 1 diabetes showed significantly greater decline in VIQ and FSIQ over time than HCs (change in VIQ, F[1, 157] = 6.47, P = 0.01; change in FSIQ, F[1, 157] = 5.22, P = 0.02). There was no significant group difference in change in PIQ (F[1, 157] = 1.28; P = 0.3).
Change in IQ Scores in Relation to Illness-related Factors
Regression analyses within the type 1 diabetes group are presented in Table 3. For any given baseline score, these models predict the IQ score at 12-year follow-up as predicted by each of the illness-related variables and covariates.
For each regression model, the overall model was significant. Baseline IQ and SES were always significantly associated with change in IQ, and length of follow-up was never significantly associated with change in IQ. A younger age at diabetes onset was significantly associated with negative change in PIQ and FSIQ. Based on the model with change in PIQ as the dependent variable, for any given PIQ score at baseline, the predicted follow-up PIQ score would be reduced by 2.36 points for each year earlier that diabetes onset occurred. Similarly, based on the model for change in FSIQ, for any given baseline FSIQ score, the predicted follow-up FSIQ score would be reduced by 0.97 points for each year earlier that diabetes onset occurred. A greater number of hypoglycemic seizures was significantly associated with negative change in VIQ. Thus, according to the model with VIQ as the dependent variable, for any given baseline VIQ score, VIQ at follow-up would be reduced by 1.19 points for each additional seizure. Metabolic control did not significantly predict change in IQ score. None of the interaction terms were significant.
Examining the Effect of Reduced HbA1c Measurements. Correlations between percentage of time HbA1c was ≥9.0% and change in VIQ, PIQ, and FSIQ conducted separately for those participants with ≥30 HbA1c values (n = 67; 70%) and those with <30 values were low for both groups (r <0.2) and not statistically significant. All regression analyses were repeated including only participants with ≥30 HbA1c values. Metabolic control still did not contribute significantly to change in VIQ, PIQ, and FSIQ (P > 0.9; P = 0.2; P = 0.4, respectively).
Potential Effect of BGL at the Time of Assessment. Mean BGL for participants with type 1 diabetes and each illness-related risk group (early or late onset, seizure history or no seizures, poor or good control) are reported in Table 2. The poor control group had significantly higher BGL prior to assessment at follow-up compared with the good control group (t[81.5] = 3.64; P < 0.001). There were no other significant group differences. Regression analyses were repeated covarying for BGL at baseline and then BGL at 12-year follow-up. Results were similar and are not reported here.
Exploration of Effect of DKA on Change in IQ. Thirty-one participants (32.6%) reported one or more episode of DKA (range 1–8; data missing on two participants). Means, SDs, and comparisons are presented in Table 4. Participants with one or more episode of DKA showed a greater loss in VIQ, PIQ, and FSIQ than participants without DKA episodes, but these were not statistically significant.
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