Table 2.
Univariate odds ratios for vitamin D deficiency (<25.0 nmol/L) in breastfeeding women
| Determinants | N | Persons at risk (% of category) | P value | Odds ratios | 95% CI | P value |
|---|---|---|---|---|---|---|
| Season | ||||||
| Summer and Autumn | 77 | 15 (19.5) | 0.021* | 1.0 | Ref. | |
| Winter and Spring | 47 | 18 (38.3) | 2.6 | 1.1, 5.8 | 0.023 | |
| Regiona | ||||||
| Latitude | / | / | / | 1.1 | 0.9, 1.3 | 0.378 |
| Longitude | / | / | / | 0.7 | 0.6, 0.9 | 0.006 |
| Skin type | ||||||
| Light | 109 | 29 (26.6) | 0.996* | 1.0 | Ref. | |
| Dark | 15 | 4 (26.7) | 1.0 | 0.3, 3.4 | 0.996 | |
| Recent holidays | ||||||
| Yes | 5 | 1 (20.0) | 0.733* | 1.0 | Ref. | |
| No | 119 | 32 (26.9) | 0.7 | 0.2, 13.7 | 0.734 | |
| Smoking | ||||||
| No | 113 | 30 (26.5) | 0.959* | 1.0 | Ref. | |
| Yes | 11 | 3 (27.3) | 1.0 | 0.3, 4.2 | 0.959 | |
| Agea | / | / | / | 0.9 | 0.9, 1.0 | 0.163 |
| BMIa | / | / | / | 1.1 | 1.0, 1.2 | 0.045 |
| Duration of breastfeeding (month)b | / | / | / | 1.0 | 1.0, 1.0 | 0.703 |
| Stage of life | ||||||
| Breastfeeding women | 124 | 16 (12.9) | 0.007* | 1.0 | Ref. | |
| NPNB women | 124 | 33 (26.6) | 2.5 | 1.3, 4.7 | 0.008 | |
25(OH)D, 25-hydroxyvitamin D; Autumn, September – November; BMI, body mass index; CI, confidence interval; NPNB, non-pregnant and non- breastfeeding; Ref., reference category with the lowest assumed prevalence of vitamin D deficiency; Spring, March – May; Summer, June – August; Winter, December – February
*Chi-square test for prevalence differences of 25(OH)D concentrations below 25 nmol/L
aOdds ratio for an increase per one unit
b n = 123