Health professional-delivered obesity prevention interventions during the first 1,000 days: a systematic review of external validity reporting [version 2; peer review: 2 approved]

Background: Childhood obesity prevention interventions delivered by
health professionals during the first 1,000 days of life show some evidence
of effectiveness, particularly in relation to behavioural outcomes. External
validity refers to how generalisable interventions are to populations or
settings beyond those in the original study. The degree to which external
validity elements are reported in such studies is unclear however. This
systematic review aimed to determine the extent to which childhood obesity
interventions delivered by health professionals during the first 1,000 days
report on elements that can be used to inform generalizability across
settings and populations.
Methods: Eligible studies meeting study inclusion and exclusion criteria
were identified through a systematic review of 11 databases and three trial
registers. An assessment tool based on the RE-AIM (Reach, Effectiveness,
Adoption, Implementation, Maintenance) framework was used to assess
the external validity of included studies. It comprised five dimensions: reach
and representativeness of individuals, reach and representativeness of
settings, implementation and adaptation, outcomes for decision making
maintenance and/or institutionalisation. Two authors independently
assessed the external validity reporting of 20% of included studies;
discrepancies were resolved, and then one completed assessments of the
remaining studies.
Results: In total, 39 trials involving 46 interventions published between
1999 and 2019 were identified. The majority of studies were randomized
controlled trials (n=24). Reporting varied within and between dimensions.
External validity elements that were poorly described included:
representativeness of individuals and settings, treatment receipt,
intervention mechanisms and moderators, cost effectiveness, and
intervention sustainability and acceptability.
Conclusions: Our review suggests that more emphasis is needed on
research designs that consider generalisability, and the reporting of
external validity elements in early life childhood obesity prevention interventions. Important gaps in external validity reporting were identified
that could facilitate decisions around the translation and scale-up of
interventions from research to practice.