A priori groups of variables used in analyses
| Variable group | Potential risk factors | Data source |
| Model 1: Maternal demographic factors | Ethnicity, whether born in the UK, education level,* maternal age,* parental employment,* financial security, size of household | BiBBS baseline questionnaire |
| Model 2: Maternal language factors | Native language, languages spoken at home | BiBBS baseline questionnaire |
| Model 3: Perinatal factors | Birth weight, preterm status | Linked health data (maternity records) |
| Model 4: Distal child factors | Child sex, child age | Linked health data (maternity records), Talking Together service data |
| Model 5: Proximal child factors | Receptive vocabulary score, parent-reported hearing concerns | Talking Together service data (Oxford CDI-Short; parent-reported questionnaire) |
For information on how data was linked, see online supplemental supporting information.
*This variable was derived using the data source listed. See online supplemental supporting information for further details.
BiBBS, Born in Bradford’s Better Start; CDI, Communicative Development Inventory.