Table 2. Association of Baseline and Year-16 Visit Characteristics With AMD: Unadjusted Model and Adjusted Model for Age, Sex, Race and Ethnicity, and Treatment Arms.
| Characteristic | No. | AMD, mean (SD) | P value | ||
|---|---|---|---|---|---|
| Without (n = 1108) | With (n = 479) | Unadjusted | Adjusteda | ||
| Age at randomization, y | 1587 | 48.0 (8.6) | 51.4 (9.6) | <.001 | NA |
| Sex, No. (%) | |||||
| Female | 1125 | 801 (71) | 324 (29) | .06 | NA |
| Male | 462 | 307 (66) | 155 (34) | ||
| Race and ethnicity, No. (%) | |||||
| African American | 333 | 241 (72) | 92 (28) | .50 | NA |
| American Indian | 126 | 90 (71) | 36 (29) | ||
| Asian | 81 | 52 (64) | 29 (36) | ||
| Hispanic | 264 | 177 (67) | 87 (33) | ||
| Non-Hispanic White | 783 | 548 (70) | 235 (30) | ||
| Education level, y | 1587 | 10.9 (3.0) | 10.6 (3.4) | .19 | .80 |
| Baseline BMI | 1587 | 33.7 (6.1) | 33.6 (6.7) | .25 | .71 |
| Baseline fasting plasma glucose, mg/dL | 1587 | 106 (8.1) | 106 (8.8) | .49 | .34 |
| Baseline 2-h plasma glucose, mg/dL | 1587 | 164 (16.5) | 165 (18.0) | .74 | .68 |
| Baseline HbA1c, % | 1583 | 5.9 (0.5) | 5.9 (0.5) | .01 | .07 |
| Baseline dietary protein intake, median (IQR), g | 1553 | 81.0 (60.8-108.4) | 78.2 (59.5-105.2) | .22 | .91 |
| Baseline weight, kg | 1587 | 92.8 (18.3) | 92.2 (19.2) | .43 | .24 |
| DPPOS variables at AMD assessment | |||||
| Follow-up weight, kg | 1587 | 91.3 (17.8) | 89.9 (19.2) | .14 | .31 |
| Follow-up HbA1c, % | 1587 | 6.1 (0.8) | 6.1 (0.7) | .50 | .72 |
| Diabetes at assessment, No. (%) | |||||
| No | 669 | 456 (68) | 213 (32) | Reference | Reference |
| Yes | 918 | 652 (71) | 266 (29) | .22 | .47 |
| Diabetic retinopathy, No. (%) | |||||
| No | 1319 | 910 (69) | 409 (31) | Reference | Reference |
| Yes | 268 | 198 (74) | 70 (26) | .11 | .07 |
| Smoking status, No. (%) | |||||
| Never | 992 | 719 (72) | 273 (28) | .001 | Reference |
| Ever | 506 | 321 (63) | 185 (37) | .02 | |
| Current | 89 | 68 (76) | 21 (24) | .23 | |
| Years with any metformin | 1587 | 8.5 (9.3) | 7.9 (9.3) | .33 | .69 |
| Years with study metformin | 1587 | 2.9 (7.0) | 2.90 (7.0) | .95 | .37 |
| Years with out-of-study metformin | 1587 | 2.9 (4.8) | 2.78 (4.8) | .23 | .71 |
Abbreviations: AMD, age-related macular degeneration; BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); DPPOS, Diabetes Prevention Program Outcomes Study; HbA1c, hemoglobin A1c, NA, not applicable.
SI conversion factors: To convert glucose to millimoles per liter, multiply by 0.0555; hemoglobin to proportion of total hemoglobin, multiply by 0.01.
For categorical variables, the unadjusted P values are calculated from Pearson χ2 tests, while the adjusted P values are calculated from logistic regressions comparing each level with the reference level. For continuous variables, the unadjusted P values are calculated from 2-sample t test or Wilcoxon rank sum test (baseline dietary protein intake), while the adjusted P values are calculated from their coefficients in the logistic regression using AMD as the outcome.