Table 2. Estimated odds ratios for overweight at age 8 years in association with BMI, weight and length trajectories from 0–24 months of age.
| Trajectory characteristicsa |
Odds ratio (95% confidence interval) of trajectory models 1–4b |
|||
|---|---|---|---|---|
| 1 | 2 | 3 | 4 | |
| BMI | ||||
| Relative BMI (size) | 1.91 (1.56–2.33)* | 2.19 (1.51–3.17)* | ||
| Relative BMI velocity (velocity) | 1.47 (1.21–1.78)* | 0.89 (0.68–1.17) | ||
| Relative timing of peak BMI velocity (timing) | 1.50 (1.24–1.81)* | 0.92 (0.69–1.22) | ||
| Length | ||||
| Relative length (size) | 1.24 (1.03–1.50)* | 1.34 (1.06–1.70)* | ||
| Relative length velocity (velocity) | 1.49 (1.23–1.79)* | 1.18 (0.74–1.88) | ||
| Relative timing of peak length velocity (timing) | 0.73 (0.61–0.87)* | 0.77 (0.49–1.23) | ||
| Weight | ||||
| Relative weight (size) | 1.74 (1.42–2.12)* | 2.02 (1.31–3.13)* | ||
| Relative weight velocity (velocity) | 1.69 (1.40–2.04)* | 1.47 (0.91–2.38) | ||
| Relative timing of peak weight velocity (timing) | 0.90 (0.76–1.07) | 0.75 (0.44–1.29) | ||
| Relative timing of peak weight velocity squaredc | 0.83 (0.73–0.95)* | |||
Abbreviation: BMI, body mass index.
Trajectory characteristics refer to size, velocity and timing estimates from SuperImposition, Translation and Rotation (SITAR) model, which estimates each child's deviation from the sample average growth curve (that is, how much bigger or smaller (size), faster or slower (velocity) and earlier or later (age at peak velocity) each child grew in relation to the sample average curve for 0–24 months of age.
Models 1–4: Model 1 includes the size parameter and covariates; Model 2 includes the velocity parameter and covariates; Model 3 includes the timing parameter and covariates; Model 4 includes size, velocity and timing parameters in addition to covariates. All models include the following covariates: age at childhood overweight measurement, sex, maternal BMI, maternal education and maternal age.
We tested quadratic terms for each of the trajectory characteristics as a test of linearity. The quadratic term was only significant and therefore only retained for the timing variable in weight trajectories.
*P<0.05.