Table 1. Baseline Characteristics of the Sample.
| Distribution of IL-6 at Age 9 ya |
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|---|---|---|---|---|
| Characteristic | Bottom Third | Middle Third | Top Third | P Valueb |
| Total No. of participants | 1590 | 1525 | 1470 | |
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| Age at outcome, mean (SD), y | 17.8 (0.36) | 17.8 (0.38) | 17.8 (0.35) | .32 |
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| Male sex, No. (%) | 944 (59.4) | 779 (51.1) | 615 (41.8) | <.001 |
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| British white ethnicity, No. (%)c | 1457 (98.0) | 1371 (98.0) | 1298 (98.0) | .41 |
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| Father’s occupation, nonmanual, No. (%)d | 885 (63.0) | 789 (61.0) | 715 (59.0) | .04 |
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| Mother’s postnatal depression score, mean (SD)e | 5.7 (4.45) | 5.9 (4.69) | 5.9 (4.60) | .23 |
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| SDQ total score at age 7 y, mean (SD) | 7.0 (4.62) | 7.3 (4.76) | 7.4 (4.81) | .08 |
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| BMI at age 9 y, mean (SD) | 16.7 (1.91) | 17.5 (2.50) | 18.5 (3.42) | <.001 |
Abbreviations: BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); IL-6, interleukin 6; SDQ, Strengths and Difficulties Questionnaire.
Cut off values for the top and bottom thirds of the distribution of IL-6 values in the total sample (cases and noncases combined) were 1.08 and 0.57 pg/mL, respectively.
One-way analysis of variance for continuous data (age, mother’s depression score, SDQ score, and BMI); χ2 test for proportions (male sex, British white ethnicity, and father’s occupation).
Data were available for 4210 participants (denominators for the bottom, middle, and top thirds were 1487, 1399, and 1324, respectively).
Data were available for 3911 participants (denominators for the bottom, middle, and top thirds were 1405,1294, and 1212, respectively).
Edinburgh Postnatal Depression Scale total score recorded at 8 weeks post partum.