Background There is growing interest and investment in linking routinely collected data across health and other public services for research. For example, several birth cohort studies gain consent from participants to link and use routine data. These data can be used to explore issues around the early years of life, which has been a key policy focus in recent years, but it is unclear whether this kind of research is translating into policy and practice.

Methods A mapping review was conducted in August 2021 to: describe how linked data research has been used in UK decision-making relating to early life health; explore factors affecting the use of linked data as evidence in these decisions; and identify knowledge gaps to inform further research. Mapping review methodology collates, describes, and catalogues the available evidence relating to a topic. Both peer reviewed and grey literature were searched using key words related to the early years of life (defined as the period from conception to age 5 years) and linked routine data. Decision-making referred to changes in policy, practice or guidelines at the local or national level. A systematic map was produced, alongside a narrative review of the findings.

Results After duplicates were removed, 2400 documents were identified. 648 full-text documents were assessed for eligibility and 8 documents were included in the review. Two documents described an evaluation of the Family Nurse Partnership using linked data, which informed local and national decision-making. Six documents referred to strategies promoting the use of linked data research, which focused on stakeholder engagement throughout the research process. Limited evidence was identified regarding the barriers to using linked data research in early years decision-making. Thus, there is a gap in the knowledge for how linked data research is used by UK early years decision-makers.

Conclusion Lack of transparency around how linked routine data has informed UK decision-making is a problem for investors as it is difficult to determine the value of linked data for early life health outcomes. If research is not being utilised by early years decision-makers, this could be a missed opportunity for better informed decision-making. It is recommended that researchers and policymakers document the use of linked data in a discoverable way.