Table 4.
Multilevel logistic regression models for prevalent eczema at follow‐up (319 of 31 036 records)
| Model 1a | Model 2b | Model 3c | |
|---|---|---|---|
| Prevalent eczema at follow‐up | Coefficient (95% CI) | Coefficient (95% CI) | Coefficient (95% CI) |
| Hard water (per 50 mg L−1 increase) | |||
| OR | – | 0·98 (0·91–1·05) | 1·00 (0·94–1·07) |
| General contextual effects | |||
| Postcode variance | 0·053 (0·005–5·25) | 0·033 (0·001–52) | 0·034 (0·001–43·2) |
| ICC | 1·6% (0·2–11·4) | 4·1% (1·4–11·6) | 1·0% (0·1–92·9) |
| Hard water (> 200 mg L−1) | |||
| OR | 0·92 (0·64–1·33) | 1·00 (0·70–1·42) | |
| General contextual effects | |||
| Postcode variance | 0·046 (0·001–9·7) | 0·043 (0·001–13·6) | |
| ICC | 1·4% (0·1–74·6) | 1·3% (0·1–80·5) | |
| Hard water groups | |||
| OR (ref. 0–60 mg L−1) | – | – | |
| 60–120 mg L−1 | 0·88 (0·66–1·18) | 0·95 (0·71–1·27) | |
| 120–180 mg L−1 | 1·34 (0·90–2·00) | 1·39 (0·93–2·07) | |
| > 180 mg L−1 | 0·90 (0·63–1·28) | 0·99 (0·70–1·39) | |
| General contextual effects | |||
| Postcode variance | 0·030 (0·001–140) | 0·029 (0·001–172) | |
| ICC | 0·9% (0·1–97·8) | 0·9% (0·1–98·1) |
Hard water values are given as the concentration of CaCO3. CI, confidence interval; ICC, intraclass correlation coefficient; OR, cluster‐specific odds ratio of the association between domestic hard water and eczema outcomes. aNull model with no covariate adjustment. bAdjusted for sex, age, ethnicity and income. cAdjusted for sex, age, ethnicity, income, Index of Multiple Deprivation and Townsend index.