Table 1.
Participant Characteristics: Vitamin B12 Status and Metformin Use by DPP Treatment Group and Study Visit
| DPP Baselinea |
DPPOS Year 1 (Mean 5 y of Follow-up) |
DPPOS Year 9 (Mean 13 y of Follow-up) |
|||||
|---|---|---|---|---|---|---|---|
| Total | MET | PLA | P Value | MET | PLA | P Value | |
| No. of participants | 1800 | 859 | 856 | 753 | 736 | ||
| Age, y | 51.2 ± 10.0 | 56.7 ± 10.1 | 56.0 ± 9.9 | n.s. | 65.5 ± 9.6 | 63.9 ± 9.7 | n.s. |
| Sex, n (%) | |||||||
| Female | 1217 (67.6) | 574 (66.8) | 586 (68.5) | n.s. | 496 (65.9) | 499 (67.8) | n.s. |
| Male | 583 (32.4) | 285 (33.2) | 270 (31.5) | n.s. | 257 (34.1) | 237 (32.2) | n.s. |
| Race/ethnicity, % non-white | 45.2 | 43.8 | 46.0 | n.s. | 45.1 | 47.1 | n.s. |
| BMI, kg/m2 | 33.6 ± 7.04 | 33.2 ± 6.9 | 33.0 ± 6.9 | .03 | 32.8 ± 6.7 | 33.5 ± 6.8 | .03 |
| HbA1c, % | 6.06 ± 1.02 | 5.90 ± 0.64 | 6.02 ± 0.74 | <.01 | 5.99 ± 0.99 | 6.15 ± 1.10 | <.01 |
| Acid suppression inhibitor use, % | 10.9 | 6.2 | 8.9 | .03 | 11.4 | 10.1 | n.s. |
| Metformin-years of exposure | 0 | 2.9 ± 1.7 | 0.1 ± 0.6 | <.01 | 9.5 ± 4.4 | 1.7 ± 2.8 | <.01 |
| Patients with diabetes, % | 0 | 33.2 | 39.0 | <.01 | 52.3 | 59.7 | <.01 |
| Vitamin B12 level, pg/mL | NM | 546 ± 337.2 | 606.6 ± 352.7 | <.01 | 615.9 ± 503.8 | 650.0 ± 498 | .19 |
| Vitamin B12 deficiency (≤ 203 pg/mL), n (%) | NM | 37 (4.3) | 20 (2.3) | .02 | 56 (7.4) | 40 (5.4) | .12 |
| Vitamin B12 deficiency or borderline-low (≤ 298 pg/mL), n (%) | NM | 164 (19.1) | 81 (9.5) | <.01 | 153 (20.3) | 115 (15.6) | .02 |
| Vitamin B12 deficiency among current active users of study metformin, n (%)b | NM | 29 (5.2) | NA | NA | 39 (9.2) | NA | NA |
| Homocysteine level, μmol/L | NM | 10.8 ± 3.6 | 10.3 ± 2.9 | <.01 | 11.7 ± 4.1 | 11.4 ± 3.9 | .09 |
| Hemoglobin, g/dl | 13.8 ± 1.3 | 13.6 ± 1.3 | 13.8 ± 1.3 | <.01 | 13.4 ± 1.2 | NM | NA |
| Hematocrit, % | 41.0 ± 3.5 | 40.6 ± 3.7 | 41.1 ± 3.6 | <.01 | 40.1 ± 3.5 | NM | NA |
| Patients with anemia, % | 9.8 | 14.3 | 10.5 | .02 | 21.0 | NA | NA |
| Patients with neuropathy, % | NM | 9.7 | 9.9 | n.s. | 13.3 | 12.9 | n.s. |
Abbreviations: MET, metformin group; PLA, placebo group; NA, not applicable; NM, not measured. Values are expressed as mean ± SD or percentage, unless described otherwise.
a
Participants with B12 measurement at DPPOS year 1, DPPOS year 9, or both.
b
Any study metformin use since last DPP visit.