Table 5.
Association between vitamin D levels and skin type, sun exposure, diet, smoking, and socioeconomic status in infants (See above for details)
| Season‐adjusted | Season + exposure + diet | All other variables | ||||||
|---|---|---|---|---|---|---|---|---|
| Factor | Levels | N | Difference | p | Difference | p | Difference | p |
| Baby‐cord blood—25OHD nmol/L | ||||||||
| Maternal age | Per year | 345 | .8 (.4–1.2) | <.001 | .5 (.1–.9) | .017 | .2 (−.3–.7) | .478 |
|
Skin type |
I | 37 | Ref | .017 | Ref | .062 | Ref | .003 |
| II | 110 | 7.4 (−.2–15) | 6.1 (−1.3–13.5) | 3.7 (−4.4–11.8) | ||||
| III | 178 | 10.2 (3–17.4) | 8.1 (1–15.2) | 10.5 (2.6–18.4) | ||||
| IV | 20 | 8.5 (−2.6–19.6) | 6.7 (−4.1–17.4) | 6.7 (−7.5–20.8) | ||||
|
Mother time outside |
<15 min | 21 | Ref | .461 | Ref | .664 | Ref | .584 |
| 15–30 min | 111 | 3.1 (−6.5–12.7) | 1.5 (−7.7–10.7) | −2.9 (−12.5–6.7) | ||||
| 30 min–2 hrs | 180 | 3.3 (−6–12.6) | 1.5 (−7.4–10.4) | −1.7 (−11.2–7.7) | ||||
| >2 hrs | 33 | 5 (−6.2–16.3) | 2.9 (−7.9–13.7) | 2.2 (−9.8–14.2) | ||||
|
Travelled abroad |
No | 292 | Ref | .003 | Ref | .029 | Ref | .355 |
| Yes | 53 | 9.1 (3.1–15.2) | 6.7 (.7–12.7) | 3 (−3.4–9.4) | ||||
| Maternal dietary intake | μg/day | 344 | .4 (−.6–1.5) | .401 | .3 (−.7–1.3) | .581 | .9 (−.1–2) | .084 |
| Maternal supplements | No | 91 | Ref | <.001 | Ref | <.001 | Ref | <.001 |
| Yes | 254 | 12.9 (8.2–17.7) | 12.2 (7.4–17) | 11.9 (5.7–18.1) | ||||
| Maternal Total intake | μg/day | 344 | 1.1 (.7–1.5) | <.001 | 1 (0.6–1.5) | <.001 | 1.1 (.6–1.7) | <.001 |
|
Mother smoker |
No | 316 | Ref | .822 | Ref | .319 | Ref | .258 |
| Yes | 29 | −.9 (−8.7–6.9) | 3.9 (−3.8–11.6) | −5.7 (−15.6–4.2) | ||||
| Infant birth weight | Per kg | 230 | 1.6 (−3.1–6.3) | .501 | 1.3 (−3.2–5.8) | .574 | 2.9 (−2.1–7.8) | .254 |
| Gestation at birth | Per week | 345 | −.3 (−2–1.4) | .745 | −.6 (−2.3–1) | .448 | −1.4 (−3.5–.7) | .179 |
|
IMD quintile |
1st | 22 | Ref | .087 | Ref | .331 | Ref | .564 |
| 2nd | 40 | 2 (−8.5–12.5) | 2.7 (−7.4–12.9) | 8 (−2.4–18.4) | ||||
| 3rd | 49 | 2 (−8.1–12.2) | 2.2 (−7.6–12.1) | 4.3 (−5.6–14.3) | ||||
| 4th | 78 | −1.5 (−11–8.1) | −.8 (−10–8.5) | .6 (−8.6–9.7) | ||||
| 5th | 149 | −3.3 (−12.3–5.7) | −.9 (−9.7–7.9) | 2.1 (−6.6–10.9) | ||||
| Baby—4 months—25OHD nmol/L | ||||||||
|
Infant time outside |
<15 min | 9 | Ref | .043 | Ref | .005 | Ref | .010 |
| 15–30 min | 80 | −19.9 (−45.4–5.7) | −5.4 (−24.5–13.7) | −4.3 (−23.5–15) | ||||
| 30 min–2 hrs | 188 | −9.6 (−34.4–15.2) | 4.3 (−14.3–22.8) | 5.5 (−13.1–24.1) | ||||
| >2 hrs | 40 | −1.3 (−28.5–26) | 9.1 (−11.2–29.5) | 8.8 (−11.7–29.2) | ||||
|
Travelled abroad |
No | 282 | Ref | .251 | Ref | .614 | Ref | .655 |
| Yes | 36 | −8.1 (−21.8–5.7) | 2.6 (−7.7–12.9) | 2.4 (−8.1–12.8) | ||||
| Baby supplements | No | 261 | Ref | .147 | Ref | .005 | Ref | .004 |
| Yes | 58 | 7.8 (−2.7–18.3) | 11.2 (3.4–19.1) | 12.1 (3.9–20.2) | ||||
|
Feeding |
Breast | 108 | Ref | <.001 | Ref | <.001 | Ref | <.001 |
| Formula | 126 | 52.7 (45.6–59.9) | 53.4 (46.2–60.5) | 55.7 (48.2–63.3) | ||||
| Mixed | 85 | 48.9 (41–56.8) | 48.6 (40.8–56.5) | 49.8 (41.9–57.8) | ||||
|
Mother smoker |
No | 285 | Ref | .236 | Ref | .288 | Ref | .38 |
| Yes | 33 | 8 (−5.3–21.4) | −5.5 (−15.6–4.7) | −4.6 (−15.1–5.8) | ||||
|
IMD quintile |
1st | 24 | Ref | .031 | Ref | .256 | Ref | .341 |
| 2nd | 43 | 10.3 (−8.2–28.9) | −.4 (−14.3–13.6) | −.7 (−14.6–13.3) | ||||
| 3rd | 56 | 4.6 (−13.1–22.3) | −7.2 (−20.4–6) | −7.3 (−20.6–5.9) | ||||
| 4th | 70 | 15.3 (−1.8–32.5) | −.4 (−13.4–12.6) | −.3 (−13.3–12.7) | ||||
| 5th | 123 | 15.7 (−.5–31.9) | −6.7 (−19.3–5.8) | −6.2 (−18.8–6.4) | ||||