Characteristics of 868 participants eligible to take study metformin* at DPPOS baseline by category of metformin adherence at >80% of prescribed dose during DPPOS
| Adherence category | (1) | (2) | (3) | (4) | P value |
| No metformin taken in DPPOS | Adherent at 0% of DPPOS visits | Adherent at >0%–<80% of DPPOS visits | Adherent at ≥80% of DPPOS visits | ||
| Number of participants | 204 | 42 | 247 | 375 | |
| Age at DPPOS baseline (years) | 0.141 | ||||
| 30–49 | 62 (23.6%) | 14 (5.3%) | 89 (33.8%) | 98 (37.3%) | |
| 50–64 | 98 (22.1%) | 19 (4.3%) | 120 (27.1%) | 206 (46.5%) | |
| ≥65 | 43 (26.9%) | 9 (5.6%) | 37 (23.1%) | 71 (44.4%) | |
| Race/ethnicity† | 0.004 | ||||
| White | 115 (23.3%) | 14 (2.8%) | 132 (26.8%) | 232 (47.1%) | |
| Black | 44 (25.6%) | 14 (8.1%) | 60 (34.9%) | 54 (31.4%) | |
| Hispanic | 25 (19.5%) | 7 (5.5%) | 35 (27.3%) | 61 (47.7%) | |
| Other‡ | 20 (26.7%) | 7 (9.3%) | 20 (26.7%) | 28 (37.3%) | |
| Sex | 0.290 | ||||
| Male | 69 (24.4%) | 11 (3.9%) | 71 (25.1%) | 132 (46.6%) | |
| Female | 135 (23.1%) | 31 (5.3%) | 176 (30.1%) | 243 (41.5%) | |
| Marital status at DPP baseline | 0.386 | ||||
| Married/Living together | 78 (26.2%) | 16 (5.4%) | 86 (28.9%) | 118 (39.6%) | |
| Single, separated, divorced, or widowed | 126 (22.1%) | 26 (4.6%) | 161 (28.2%) | 257 (45.1%) | |
| Marital status at DPPOS baseline | 0.145 | ||||
| Married/Living together | 83 (26.9%) | 17 (5.5%) | 89 (28.9%) | 119 (38.6%) | |
| Single, separated, divorced, or widowed | 120 (21.5%) | 25 (4.5%) | 157 (28.1%) | 256 (45.9%) | |
| Educational status at DPP baseline | 0.490 | ||||
| ≤ High School | 43 (20.5%) | 15 (7.1%) | 60 (28.6%) | 92 (43.8%) | |
| Attended College | 102 (24.5%) | 20 (4.8%) | 116 (27.9%) | 178 (42.8%) | |
| Attended Graduate School | 59 (24.4%) | 7 (2.9%) | 71 (29.3%) | 105 (43.4%) | |
| Educational status at DPPOS baseline | 0.126 | ||||
| <High School | 37 (17.8%) | 15 (7.2%) | 59 (28.4%) | 97 (46.6%) | |
| Attended College | 111 (26.4%) | 19 (4.5%) | 122 (29.0%) | 169 (40.1%) | |
| Attended Graduate School | 55 (23.2%) | 8 (3.4%) | 65 (27.4%) | 109 (46.0%) | |
| Employment at DPP baseline | 0.682 | ||||
| Full or part time | 153 (23.0%) | 30 (4.5%) | 191 (28.7%) | 292 (43.8%) | |
| Retired | 31 (27.2%) | 6 (5.3%) | 27 (23.7%) | 50 (43.9%) | |
| Other§ | 20 (22.7%) | 6 (6.8%) | 29 (33.0%) | 33 (37.5%) | |
| Employment status at DPPOS baseline¶ | 0.003 | ||||
| Full or part time | 134 (21.8%) | 26 (4.2%) | 185 (30.1%) | 269 (43.8%) | |
| Retired | 43 (24.9%) | 12 (6.9%) | 33 (19.1%) | 85 (49.1%) | |
| Other§ | 26 (32.9%) | 4 (5.1%) | 28 (35.4%) | 21 (26.6%) | |
| Income status at DPP baseline | 0.076 | ||||
| <$20 000 | 23 (22.5%) | 6 (5.9%) | 27 (26.5%) | 46 (45.1%) | |
| $20–$75 000 | 130 (25.8%) | 26 (5.2%) | 144 (28.6%) | 203 (40.4%) | |
| >$75 000 | 31 (15.9%) | 7 (3.6%) | 56 (28.7%) | 101 (51.8%) | |
| Early metformin adherence at 3 months in DPP** | §amp;lt;0.001 | ||||
| Non-adherent | 83 (34.6%) | 18 (7.5%) | 73 (30.4%) | 66 (27.5%) | |
| Early adherent | 110 (18.2%) | 20 (3.3%) | 169 (28.0%) | 304 (50.4%) | |
| Mental Component Score of SF-36 | |||||
| DPP baseline | 54.1 ± 7.3 | 53.4 ± 8.6 | 53.4 ± 8.8 | 54.6 ± 7.3 | 0.305 |
| Mean score during DPPOS | 53.9 ± 7.1 | 52.3 ± 7.0 | 52.9 ± 6.9 | 54.1 ± 6.4 | 0.109 |
| Physical Component Score of SF-36 | |||||
| DPP baseline | 50.4 ± 7.4 | 49.4 ± 7.5 | 50.0 ± 7.4 | 50.5 ± 6.8 | 0.746 |
| Mean score during DPPOS†† | 46.4 ± 8.3 | 46.5 ± 8.8 | 46.6 ± 8.0 | 48.2 ± 7.1 | 0.028 |
| Beck Anxiety Score†† | |||||
| Median DPP baseline | 2.0 (0.0, 5.0) | 3.0 (1.0, 6.0) | 3.0 (1.0, 6.0) | 2.0 (0.0, 5.0) | 0.313 |
| Median score during DPPOS | 3.0 (1.1, 5.6) | 3.9 (1.8, 5.8) | 3.4 (1.6, 6.1) | 2.8 (1.2, 5.2) | 0.060 |
| Beck Depression Score‡‡ | |||||
| Median DPP baseline | 4.0 (1.0, 7.0) | 3.0 (1.0, 7.0) | 4.0 (1.0, 7.0) | 3.0 (1.0, 6.0) | 0.438 |
| Median score during DPPOS¶ | 3.1 (1.5, 6.0) | 3.8 (1.6, 7.2) | 3.8 (2.1, 6.6) | 2.7 (1.1, 5.5) | 0.001 |
| Number of concomitant medications | |||||
| Median DPP baseline | 0.0 (0.0, 2.0) | 0 (0.0, 1.0) | 1.0 (0.0, 2.0) | 1.0 (0.0, 2.0) | 0.063 |
| Median during DPPOS | 2.2 (0.9, 3.9) | 2 (1.2, 4) | 2.6 (1.3, 4.3) | 2.7 (1.4, 4.3) | 0.105 |
Percentages add to 100% across each row. Other statistics are mean±SD, or median (25th, 75th percentiles).
Significant pairwise tests (Holm adjusted) of column groups for covariates with significant overall p values (ANOVA for continuous variables, χ² tests for categorical variables).
DPP baseline data are included when DPPOS baseline data are not available and when a comparison to DPPOS mean data is appropriate.
*DPPOS metformin participants who had a fasting plasma glucose ≥140 mg/dL during DPP were ineligible to continue study metformin during DPPOS. They were advised to consult their private physicians for treatment of their diabetes. Participants with a new diagnosis of diabetes during DPPOS are included until they reach an A1c threshold of 7%.
†Significant pairwise comparisons: 2 vs 4 (p<0.05).
‡Combined Asian and American Indians due to small cell size.
§Unemployed, homemaker, student, seasonally employed, never worked, and other.
¶Significant pairwise comparisons: 3 vs 4 (p<0.05).
**Significant pairwise comparisons: 1 vs 3 (p< 0.05); 1 vs 4 (p< 0.05); 2 vs 4 (p< 0.05); 3 vs 4 (p<0.05).
††Significant pairwise comparisons: No pairwise comparisons significant.
‡‡The Beck depression and anxiety scores were calculated from the standard 21-question inventory for each.
ANOVA, analysis of variance; DPP, Diabetes Prevention Program; DPPOS, DPP Outcomes Study; SF-36, Short Form-36.