Table 2.
Mixed model analysis of the SDQ total difficulties score and subscales
| Extremely preterm participants compared to term-born controls | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Parameter | SDQ total difficulties score (n = 443) | Emotional symptoms score (n = 443) | Conduct problems score (n = 443) | Hyperactivity/inattention score (n = 444) | Peer problems score (n = 443) | |||||
| Estimate | 95% CI | Estimate | 95% CI | Estimate | 95% CI | Estimate | 95% CI | Estimate | 95% CI | |
| Constant | 7.62 | (6.87 to 8.38) | 1.85 | (1.58 to 2.13) | 1.50 | (1.29 to 1.72) | 3.13 | (2.75 to 3.50) | 0.95 | 0.75 to 1.15) |
| EPT | 4.81 | (3.76 to 5.87) | 0.67 | (0.29 to 1.05) | 0.75 | (0.42 to 1.07) | 2.33 | (1.84 to 2.83) | 1.37 | (1.05 to 1.68) |
| AGE | − 0.40 | (− 0.57 to − 0.23) | − 0.08 | (− 0.15 to − 0.01) | − 0.14 | (− 0.20 to − 0.09) | − 0.18 | (− 0.26 to − 0.11) | 0.05 | (0.03 to 0.07) |
| EPT*AGE | – | – | 0.06 | (0.01 to 0.11) | − 0.05 | (− 0.09 to − 0.02) | − 0.07 | (− 0.12 to − 0.02) | – | – |
| AGE2 | 0.03 | (0.02 to 0.04) | 0.008 | (0.003 to 0.013) | 0.01 | (0.007 to 0.014) | 0.01 | (0.01 to 0.02) | – | – |
| Extremely preterm participants only | |||||
|---|---|---|---|---|---|
| SDQ Total Difficulties Score adjusted for CBCL at 2.5 years (n = 235) | SDQ Total Difficulties Score adjusted for moderate/severe cognitive impairment at last clinical assessment (n = 249) | ||||
| Parameter | Estimate | 95% CI | Parameter | Estimate | 95% CI |
| Constant | 10.84 | (8.99 to 11.81) | Constant | 10.37 | (9.22 to 11.51) |
| AGE | − 0.37 | (− 0.60 to − 0.14) | Age | − 0.33 | (− 0.55 to − 0.10) |
| AGE2 | 0.03 | (0.01 to 0.04) | Age2 | 0.02 | (0.01 to 0.04) |
| CBCL clinically significant at 2.5 years | 6.90 | (5.10 to 8.70) | Moderate/severe cognitive impairment at last assessment | 4.27 | (2.76 to 5.77) |
EPT is the group term that tests for the difference in scores at age 6 between the EPT and control group (intercept)
The AGE term is the increase in scores per year of age from the age of 6
The EPT*AGE term tests whether the scores in EPT and control group have different trajectories over time (slope)
The AGE2 term tests whether the trajectories depart from a straight linear line (curvature)
For example, for the SDQ total difficulties score: The EPT group score is 4.81 points higher than the control group mean score of 7.62 at age 6 and scores decrease in both groups by around 0.4 points per year of age; however, there is no difference in the slope of the trajectories between groups as the EPT*AGE term is not significant
CBCL child behavior checklist, EPT extremely preterm, SDQ strengths and difficulties questionnaire