Table 2. Summary of variables used as exposures.
Other than household income (measured when study children were aged 3/4 years) and partner financial difficulties (measured 8 months post-partum), all variables were assessed in pregnancy or shortly after.
| Variable ( variable name) | Variable coding | Notes |
|---|---|---|
| Demographic variables | ||
| Age ( AgeAtBirth; AgeInPreg for partners) | Continuous (years) | |
| Ethnicity ( nonWhiteEthnic) | Binary (White vs Other than White) | Also used recent COVID4
questionnaire to fill in missing data |
| Marital status ( maritalStatus) | Unordered category (never married vs currently married vs
widowed/divorced/separated) |
|
| Residential mobility (in last 5 years; mobility) | Ordered category (0 moves vs 1 move vs 2 moves vs 3
moves vs 4 moves vs 5 or more moves) |
|
| Urban/rural status ( rural) | Binary (town/village/hamlet vs urban) | For partners, using
mothers data |
| Parity ( parity) | Ordered category (0 vs 1 vs 2 or more) | For partners, using
mothers data |
| Socioeconomic variables | ||
| Highest education qualification ( education) | Ordered category (CSE/none vs vocational vs O-level vs
A-level vs degree) a |
|
| Mother’s highest education qualification
( maternalEdu) |
Ordered category (CSE/none vs vocational vs O-level vs
A-level vs degree) a |
|
| Father’s highest education qualification
( paternalEdu) |
Ordered category (CSE/none vs vocational vs O-level vs
A-level vs degree) a |
|
| Occupational social class ( highSocClass) | Binary (low [III manual/IV/V] vs high [I/II/III non-manual]) b | |
| Mother’s occupational social class
( highSocClass_mat) |
Binary (low [III manual/IV/V] vs high [I/II/III non-manual]) b | |
| Father’s occupational social class
( highSocClass_pat) |
Binary (low [III manual/IV/V] vs high [I/II/III non-manual]) b | |
| Household income ( income) | Continuous (log income per/week) | |
| Index of multiple deprivation ( IMD) | Ordered category (1
st quintile [least deprived] vs 2
nd quintile
vs 3 rd quintile vs 4 th quintile vs 5 th quintile [most deprived]) |
For partners, using
mothers data |
| Townsend deprivation index ( townsendDep) | Ordered category (1
st quintile [least deprived] vs 2
nd quintile
vs 3 rd quintile vs 4 th quintile vs 5 th quintile [most deprived]) |
For partners, using
mothers data |
| Mother or partner access to car ( accessToCar) | Binary (yes vs no) | |
| Housing status ( housing) | Unordered category (owned/mortgaged vs renting vs
council/housing association vs other) |
For partners, using
mothers data |
| Recent financial difficulties ( financeDiffs) | Binary (yes vs no) | |
| Financial difficulties score ( financeDiffsScore) | Continuous (from 0 [no difficulties] to 15 [severe
difficulties]) |
|
| Family’s financial circumstances got worse
during childhood ( poorerChildhood) |
Binary (yes vs no) | |
| Crowding index ( crowding) | Ordered category (calculated by dividing the number of
people in the household by the number of rooms; ≤ 0.5; > 0.5 to 0.75; > 0.75 to 1; > 1) |
For partners, using
mothers data |
| Self-reported neighbourhood quality index
( neighPercept) |
Continuous (score from 0 [low quality neighbourhood] to 12
[high quality neighbourhood]) |
|
| Partner absence in pregnancy
( partnerAbsence) |
Binary (partner present vs partner absent) | Not applicable for
partners |
a CSE = Certificate of Secondary Education qualification (examinations sat at the end of secondary school at approx. age 16; compulsory from the early 1970s, unless completing O-level qualifications instead); O-level = Ordinary level qualifications (examinations sat at the end of secondary school, often for more academically-able pupils at approx. age 16); A-level = Advanced level qualification (non-compulsory examinations sat at the end of college or sixth form at approx. age 18).
b For more information on these occupational social classes, see: https://sru.soc.surrey.ac.uk/SRU9.html.