Table 4.
Changes in β-cell function over time among those with 25(OH)D < 20 ng/mL at baseline
| Baseline | Month 12 | Month 24 | Average percent difference compared with baseline (95% CI)a | Overall (unadjusted) least-squares mean percent difference for vitamin D vs placebo (95% CI)b | |
|---|---|---|---|---|---|
| DIcpep | |||||
| Vitamin D | 102.2 (70.3, 147.7) | 95.4 (66.3, 153.3) | 101.5 (64.8, 137.4) | -0.3% (-2.8 to 2.2) | 1.6% (-2.2 to 5.3) |
| n | 204 | 201 | 145 | ||
| Placebo | 107.4 (69.4, 155.4) | 94.4 (59.9, 151.0) | 100.1 (60.4, 146.2) | -1.9% (-4.7 to 0.9) | |
| n | 171 | 168 | 112 | ||
| P value | 0.75 | 0.71 | 0.72 | ||
| DIins | |||||
| Vitamin D | 5695.7 (3763.2, 8420.3) | 5189.8 (3698.4, 8929.8) | 5421.2 (3467.8, 8847.0) | -0.3% (-6.1 to 5.5) | 7.5% (-1.2 to 16.2) |
| n | 204 | 201 | 145 | ||
| Placebo | 5660.6 (3745.2, 8636.4) | 4882.5 (2919.9, 8664.8) | 5217.8 (3298.7, 8757.4) | -7.8% (-14.3 to -1.3) | |
| n | 171 | 168 | 112 | ||
| P value | 0.97 | 0.22 | 0.48 |
Data are presented as median (IQR). P values for each visit are from Wilcoxon rank sum test.
Abbreviations: DIcpep, change in the disposition index for C peptide; DIins, disposition index using insulin-based indices; IQR, interquartile range.
a Average percent difference compared with baseline is based on linear mixed model for repeated measures data.
b Unadjusted between-group difference in least square means using all available visits.