Table 3.
Determinants of vitamin D status in IBD patients stratified by season
| End of summer | End of winter | p valuesa | ||||||
|---|---|---|---|---|---|---|---|---|
| Total | Vitamin D deficiency <50 nmol/L | Vitamin D adequacy ≥50 nmol/L | Total | Vitamin D deficiency <50 nmol/L | Vitamin D adequacy ≥50 nmol/L | Vitamin D deficiency vs. adequacy | ||
| n = 316 | n = 122 | n = 194 | n = 281 | n = 160 | n = 121 | Summer | Winter | |
| Oral vitamin D supplementation, n (%) | 106 (33.5) | 32 (26.6) | 74 (38.1) | 117 (43.5) | 53 (34.6) | 64 (55.2) | 0.029 | <0.001 |
| Fatty fish intake, units/month (SD) | 2.6 (2.5) | 2.7 (2.8) | 2.5 (2.0) | 2.6 (2.2) | 2.8 (2.4) | 2.5 (2.0) | NS | NS |
| Outdoor activities at least 2 h a day, days/week (SD) | 5.4 (2.1) | 5.3 (2.1) | 5.5 (2.1) | 3.0 (2.5) | 3.1 (2.5) | 2.9 (2.5) | NS | NS |
| Recent sun holiday, n (%) | 138 (44.5) | 39 (33.1) | 99 (51.6) | 28 (10.1) | 11 (7.0) | 17 (14.3) | <0.001 | 0.047 |
| Regular solarium visits, n (%) | 64 (20.6) | 14 (11.9) | 50 (26.0) | 28 (10.1) | 7 (4.5) | 21 (17.6) | 0.003 | 0.012 |
| Serum 25OHD level, nmol/L (SD) | 55.1 (16.4) | 39.1 (7.8) | 65.1 (11.8) | 48.4 (20.0) | 35.6 (11.0) | 65.5 (16.0) | – | – |
aStatistical analyses were performed by using a parametric test (unpaired t test) when a normal distribution was present and when in order a non-parametric test (Mann–Whitney U) to assess univariate significant associations between the stated continuous determinants and vitamin D deficiency. Categorical determinants were analysed by using Pearson’s Chi-square test (or Fisher’s exact test when expected frequencies were low). All p values >0.10 are noted as NS (non-significant). All p values between 0.5 and 0.10 are noted in order to evaluate non-significant trends associated with vitamin D deficiency