Effectiveness of a telephone-based randomised clinical trial targeting obesity risk of preschool-aged children: An extension study during the COVID-19 pandemic.

Background: There is a great need for determining the effectiveness of telephone-based early obesity interventions targeting preschool-aged children. This was particularly important during the COVID-19 pandemic when most face-to-face health promotion programs were suspended. The aim of this study was to determine the effects of a two-year telephone-based intervention on body mass index (BMI), eating habits, active play, and screen time behaviours among preschool-aged children.

Methods: We conducted an extension study to a randomised controlled trial (RCT) with 662 mother-child dyads at ages 2-3 years in 2019-20 in the Greater Sydney metropolitan area of New South Wales (NSW), Australia. In 2020-22, we extended the RCT for another two years, with one-year intervention (3-4 years) and one-year follow-up (4-5 years). Participants remained in the same group allocation as the original trial. The intervention comprised five nurse-led telephone support calls and SMS plus mailed intervention booklets to mothers to promote the health behaviours of their children from ages 2 to 4 years. The primary outcome was children's BMI, with weight and height measured at ages 3, 4, and 5 years. We conducted intention-to-treat analysis with a multiple imputation approach. Mixed linear models were built to compare the outcomes between intervention and control groups. Sub-group analysis by household income was also conducted.

Results: Of the 662 mothers, 537 (81%), 491 (74%), and 405 (61%) completed the assessments when their children were 3, 4, and 5 years old. The intervention was significantly associated with a lower mean BMI: 15.90 (SE 0.08) vs. 16.20 (SE 0.08), difference -0.30 (95% CI: -0.59 to -0.01, P = 0.039). This association was stronger among low-income families, difference -0.57 (95% CI: -1.05 to -0.10, P = 0.018).

Conclusions: The two-year telephone-based intervention was associated with decreased mean BMI of preschool-aged children. Telephone-based support for mothers could reduce obesity risk in preschool-aged children, particularly among low-income families.

Trial registration: The original RCT is registered with the Australian Clinical Trial Registry (ACTRN12618001571268).