Evaluating dose delivered of a behavioral intervention for childhood obesity prevention: a secondary analysis

Abstract

Background: Current recommendations for intensive behavioral interventions for childhood obesity treatment do not account for variable participant attendance, optimal duration of the intervention, mode of delivery (phone vs. face-to-face), or address obesity prevention among young children. A secondary analysis of an active one-year behavioral intervention for childhood obesity prevention was conducted to test how "dose delivered" was associated with body mass index z-score (BMI-Z) across 3 years of follow-up.

Methods: Parent-child pairs were eligible if they qualified for government assistance and spoke English or Spanish. Children were between three and 5 years old and were at risk for but not yet obese (BMI percentiles ≥50th and < 95th). The intended intervention dose was 18 h over 3-months via 12 face-to-face "intensive sessions" (90 min each) and 6.75 h over the next 9 months via 9 "maintenance phone calls" (45 min each). Ordinary least-squares multivariable regression was utilized to test for associations between dose delivered and child BMI-Z immediately after the 1-year intervention, and at 2-, and 3-year follow-up, including participants who were initially randomized to the control group as having "zero" dose.

Results: Among 610 parent-child pairs (intervention n = 304, control n = 306), mean child age was 4.3 (SD = 0.9) years and 51.8% were female. Mean dose delivered was 10.9 (SD = 2.5) of 12 intensive sessions and 7.7 (SD = 2.4) of 9 maintenance calls. Multivariable linear regression models indicated statistically significant associations of intensive face-to-face contacts (B = -0.011; 95% CI [- 0.021, - 0.001]; p = 0.029) and maintenance calls (B = -0.015; 95% CI [- 0.026, - 0.004]; p = 0.006) with lower BMI-Z immediately following the 1-year intervention. Their interaction was also significant (p = 0.04), such that parent-child pairs who received higher numbers of both face-to-face intensive sessions (> 6) and maintenance calls (> 8) were predicted to have lower BMI-Z. Sustained impacts were not statistically significant at 2- or 3-year follow-up.

Conclusions: In a behavioral intervention for childhood obesity prevention, the combination of a modest dose of face-to-face sessions (> 6 h over 3 months) with sustained maintenance calls (> 8 calls over 9 months) was associated with improved BMI-Z at 1-year for underserved preschool aged children, but sustained impacts were not statistically significant at 2 or 3 year follow-up.

Clinical trial registration: The trial was registered on ClinicalTrials.gov (NCT01316653) on March 16, 2011, which was prior to participant enrollment.

Keywords: Behavioral interventions; Childhood obesity; Dose intensity.

Conflict of interest statement

Dr. Heerman is an associate editor for BMC Public Health. Dr. Heerman had no role in the review or editorial decision for the publication of this manuscript. The authors declare that they have no other competing interests.

Figures

Fig. 1

Study design of the GROW trial, indicating intended dose and data collection time points. At 12-month follow-up, 90.4% (275/304) of participants were retained in the intervention condition and 90.2% (276/306) of participants were retained in the control condition

Fig. 2

Contour plot of model-based estimates of child BMI-Z score immediately following the 1-year intervention. Children with high levels of both intensive face-to-face and maintenance phone calls had the lowest predicted BMI-Z. The data table shows predicted BMI-Z values for representative combinations of intensive and maintenance dose. This model included the main effects of face-to-face dose, maintenance dose, and their interaction, controlling for baseline child BMI-Z, child age, child gender, and parent race/ethnicity. To estimate predicted values, the following covariate profile was selected: males with the mean baseline BMI-Z, mean baseline age, who had parents of Hispanic, Mexican origin. Models using a variety of other covariate profiles generated similar results. Predicted estimates are not shown when beyond the bounds of the dose combinations present in the data (e.g., combinations of many face-to-face sessions and few maintenance phone calls). See Additional file 1 for complete distribution of dose received and additional file 5 for predicted estimates at each specific dose combination

Fig. 3

Contour plot of model-based estimates for the probability of at least a 0.1 decrease in BMI-Z immediately following the 1-year intervention. Children with high levels of both intensive face-to-face and maintenance phone calls had the highest probability of decreasing BMI-Z immediately following the 1-year intervention. The data table shows predicted probabilities for representative combinations of intensive and maintenance dose. This model included the main effects of face-to-face dose, maintenance dose, and their interaction, controlling for baseline child BMI-Z, child age, child gender, and parent race/ethnicity. To estimate predicted values, the following covariate profile was selected: males with the mean baseline BMI-Z, mean baseline age, who had parents of Hispanic, Mexican origin. Models using a variety of other covariate profiles generated similar results. Predicted estimates are not shown when beyond the bounds of the dose combinations present in the data (e.g., combinations of many face-to-face sessions and few maintenance phone calls). See Additional file 1 for complete distribution of dose received and additional file 5 for predicted estimates at each specific dose combination