Generational differences in the associations between early-life characteristics and adult SEP measured by Hollingshead index, the Uppsala Multi-generational birth cohort, Sweden (n=16 288)
| Early-life characteristics* | Model 1† | Model 2‡ | ||||
| Generation 1 | Generation 2 | Difference in association | Generation 1 | Generation 2 | Difference in association | |
| ß(95% CI)§ | ß(95% CI)§ | ß change
(95% CI)¶ | ß(95% CI)§ | ß(95% CI)§ | ß change
(95% CI)¶ | |
| Family SEP | ||||||
| High | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. |
| Medium | −24.9
(–26.8 to –23.1) | −10.8
(–12.7 to –8.9) |
14.1
(11.4 to 16.8)** | −24.9
(–26.8 to–23.0) | −10.8
(–12.8 to –8.9) |
14.1
(11.4 to 16.7)** |
| Low | −30.3
(–32.1 to –28.4) | −13.7
(–15.4 to –12.1) |
16.5
(14.0 to 19.0)** | −29.4
(–20.7 to –18.2) | −13.6
(–15.3 to –12.01) |
15.8
(13.3 to 18.3)** |
| Mother’s marital status | ||||||
| Married | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. |
| Unmarried | −5.9
(−7.2 to –4.7) | −7.4
(−9.4 to –5.3) | −1.5 (−3.8 to 1.0)** | −1.0 (−2.4 to 0.3) | −6.9
(−8.9 to –4.9) | −5.9
(–8.2 to –3.4)** |
| Mother’s parity | ||||||
| 1 | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. |
| 2 | −2.1
(−3.3 to –0.9) | −3.4
(−4.7 to –2.1) | −1.3 (−3.0 to 0.5) | −4.3
(−5.5 to –3.1) | −4.6
(−5.9 to –3.3) | −0.3 (−2.0 to 1.4) |
| ≥3 | −7.7
(−8.8 to –6.6) | −8.2
(−9.9 to –6.5) | −0.5 (−2.6 to 1.5) | −11.4
(–12.7 to –10.2) | −9.6
(–11.3 to –7.9) | 1.8 (−0.2 to 3.8) |
| Birth weight (standardised) | ||||||
| SGA | −2.9
(−4.7 to –1.2) | −1.6** (−3.8 to 0.5) | 1.3 (−1.4 to 4.1) | −3.00
(−4.6 to –1.4) | −1.5** (−3.6 to 0.5) | 1.5 (−1.1 to 4.1) |
| Normal | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. |
| LGA | −0.1 (−2.6 to 0.7) | 1.4 (−0.8 to 3.6) | 2.4 (−0.3 to 5.2) | −0.1 (−1.6 to 1.5) |
2.5
(0.4 to 4.6) | 2.6 (−0.0 to 5.2) |
| Length of gestation | ||||||
| Preterm (≤36 weeks) | −1.2 (−3.1 to 0.8) | −1.6 (−4.5 to 1.3) | −0.4 (−3.91 to 3.07) | −0.1 (−2.0 to 1.7) | −1.3 (−4.1 to 1.4) | −1.2 (−4.4 to 2.1) |
| Term (37–41 weeks) | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. |
| Post-term (≥42 weeks) | −3.1
(−4.6 to –1.6) | −2.6
(−4.6 to –0.4) | 0.5 (−2.03 to 2.96) | −2.3
(−3.7 to –0.9) | −1.7 (−3.5 to 0.2) | 0.6 (−1.7 to 2.9) |
| Multiplicity of birth | ||||||
| Singleton | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. |
| Twin/triplet | −2.8 (−6.6 to 0.9) | −6.0
(–11.6 to –0.4) | −3.2 (−9.9 to 3.5) | −2.7 (−6.1 to 0.7) | −4.5 (−10.1 to 1.1) | −1.8 (−8.3 to 4.7) |
| Mother’s age (years) at birth | ||||||
| <20 | −4.6
(−6.9 to –2.2) | −7.1
(−9.5 to –4.7) | −2.5 (−5.9 to 0.8) | 0.3 (−2.1 to 2.7) | −5.7
(−8.1 to –3.3) | −6.0
(−9.3 to –2.7) |
| 20–24 | −2.9
(−4.3 to –1.6) | −3.7
(−5.3 to –2.2) | −0.8 (−2.8 to 1.2) | −0.5 (−1.8 to –0.8) | −2.9
(−4.4 to –1.5) | −2.4
(−4.2 to –0.5) |
| 25–29 | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. |
| 30–34 | 1.0 (−0.4 to 2.5) | 0.7 (−1.2 to 2.5) | −0.3 (−2.7 to 2.0) | 0.2 (−1.1 to 1.5) | 0.8 (−1.0 to 2.6) | 0.6 (−1.7 to 2.8) |
| ≥35 | −1.7
(−3.2 to –0.2) | −1.0 (−4.3 to 2.4) | 0.7 (−2.9 to 4.4) | −2.6
(−4.0 to –1.1) | −0.9 (−4.1 to 2.4) | 1.7 (−1.8 to 5.2) |
Bold typeface indicates statistical significance (p<0.05).
*Each exposure represents a separate linear regression model.
†Model 1 statistically adjusted for year of birth (gender was also adjusted for to estimate the effect of length of gestation).
‡Model 2 additionally adjusted for different sets of confounders for different exposures. The associations with family SEP and mother’s marital status were estimated by adjusting for each other. The association with mother’s parity was estimated by adjusting for family SEP, multiplicity of birth, mother’s marital status and mother’s age at child birth. The associations with standardised birth weight, length of gestation and multiplicity of births were estimated by adjusting for all exposures. The association with mother’s age at birth was adjusted for family SEP and mother’s marital status. An exposure*generation interaction term was fitted in all models to assess if the associations vary by generation. Since a significant interaction between family SEP and generation was detected in Model 1, this interaction was adjusted for in Model 2 when appropriate.
§Obtained in post-estimation from the fitted linear regression models.
¶Obtained from linear regression models by fitting an interaction term of exposure*generation.
**Estimates modified by gender: p value for family SEP*generation*gender=0.009; p value for marital status*generation*gender=0.016. See also table 3.
ß, beta coefficient; LGA, large-for-gestational age; Ref., reference group; SEP, socioeconomic position; SGA, small-for-gestational age.