Table 2.
Changes in insulin sensitivity and β-cell function over time
| 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 | |
|---|---|---|---|---|---|
| HOMA2%Scpep | |||||
| Vitamin D | 17.1 (13.2, 22.4) | 16.8 (13, 22.3) | 16.9 (13.1, 22.4) | -1.0% (-2.1 to 0.0) | 0.1% (-1.4 to 1.5) |
| n | 888 | 886 | 696 | ||
| Placebo | 16.9 (13.3, 21.4) | 16.8 (12.6, 22.5) | 16.5 (12.8, 21.4) | -1.0% (-2.1 to 0.0) | |
| n | 886 | 877 | 665 | ||
| P value | 0.32 | 0.56 | 0.16 | ||
| HOMA2%Sins | |||||
| Vitamin D | 62.0 (43.1, 91.1) | 63.1 (41.8, 95.4) | 65.2 (42.4, 93.9) | -0.1% (-2.3 to 2.2) | -0.6% (-3.8 to 2.6) |
| n | 888 | 886 | 696 | ||
| Placebo | 59.2 (40.8, 87.7) | 61.5 (39.1, 91.1) | 60.1 (41.4, 88.2) | 0.5% (-1.7 to 2.8) | |
| n | 886 | 877 | 665 | ||
| P value | 0.03 | 0.12 | 0.07 | ||
| CPI | |||||
| Vitamin D | 5.9 (3.9, 8.7) | 5.86 (3.8, 8.5) | 5.84 (3.7, 8.4) | -1.6% (-2.7 to -0.5) | -0.8% (-2.4 to 0.8) |
| n | 888 | 864 | 670 | ||
| Placebo | 5.8 (4.1, 8.3) | 5.9 (3.9, 8.5) | 5.8 (3.9, 8.2) | -0.8% (-2.0 to 0.3) | |
| n | 886 | 861 | 642 | ||
| P value | 0.64 | 0.61 | 0.995 | ||
| IGI | |||||
| Vitamin D | 91.2 (55.5, 152.4) | 90.2 (52.2, 145.6) | 87.8 (50.2, 144.9) | -2.6% (-3.9 to -1.3) | -0.9% (-2.7 to 0.9) |
| n | 888 | 864 | 670 | ||
| Placebo | 95.7 (60.3, 148.7) | 90.6 (56.6, 149.5) | 89.19 (53.9, 147.2) | -1.7% (-3.0 to -0.5) | |
| n | 886 | 861 | 642 | ||
| P value | 0.32 | 0.44 | 0.59 | ||
| DIcpep | |||||
| Vitamin D | 100.2 (66.4, 146.3) | 94.6 (63.5, 147.6) | 96.5 (62.3, 141.2) | -1.2% (-2.3 to -0.1) | -0.8% (-2.4 to 0.8) |
| n | 888 | 864 | 670 | ||
| Placebo | 98.4 (67.9, 144.1) | 96.1 (62.3, 148.3) | 93.0 (59.9, 143.6) | -0.4% (-1.5 to 0.7) | |
| n | 886 | 861 | 642 | ||
| P value | 0.51 | 0.87 | 0.61 | ||
| DIins | |||||
| Vitamin D | 5641.4 (3741.9, 8662.1) | 5365.4 (3488.1, 8922.3) | 5401.1 (3369.5, 8422.7) | -3.7% (-6.2 to -1.2) | -1.5% (-5.1 to 2.1) |
| n | 888 | 864 | 670 | ||
| Placebo | 5571.9 (3615.9, 8191.7) | 5383.1 (3346.4, 8859.2) | 5293.2 (3430.2, 8505.8) | -2.2% (-4.8 to 0.3) | |
| n | 886 | 861 | 642 | ||
| P value | 0.30 | 0.69 | 0.45 | ||
| HOMA2%Bcpep | |||||
| Vitamin D | 235.5 (190.0, 285.9) | 235.7 (192.1, 287.5) | 229.7 (186.3, 275.3) | -0.8% (-1.8 to 0.2) | 0.7% (-0.7 to 2.0) |
| n | 888 | 886 | 696 | ||
| Placebo | 236.45 (194.1, 286.5) | 237 (194.6, 289.1) | 233 (191.8, 276.5) | -1.5% (-2.4 to -0.5) | |
| n | 886 | 877 | 665 | ||
| P value | 0.28 | 0.55 | 0.26 | ||
| HOMA2%Bins | |||||
| Vitamin D | 90.6 (68.3, 119.9) | 90.5 (69.5, 116.6) | 86.4 (66, 113.6) | -2.1% (-3.8 to -0.5) | 1.8% (-0.5 to 4.2) |
| n | 888 | 886 | 696 | ||
| Placebo | 94.6 (71.7, 125.3) | 91.8 (70.3, 123.3) | 90.3 (67.7, 113.5) | -4.0% (-5.6 to -2.3) | |
| n | 886 | 877 | 665 | ||
| P value | 0.02 | 0.13 | 0.08 |
Data are presented as median (IQR). P values for each visit are from Wilcoxon rank-sum test.
Abbreviations: CPI, C-peptide index; DIins, disposition index using insulin-based indices; HOMA2%Bcpep, Homeostasis Model Assessment of β-cell function using C-peptide values; HOMA2%Bins, Homeostasis Model Assessment of β-cell function using insulin values; HOMA2%Scpep, Homeostasis Model Assessment of steady-state insulin sensitivity derived from C-peptide values; HOMA2%Sins, Homeostasis Model Assessment of β-cell function derived from insulin values; IGI, insulinogenic index; 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.