Table 2.
Characteristics of patients ≥50 years old and free of dementia with an HbA1c between 6.5 and < 9.5 from the Veterans Health Administration (VHA; FY2002 to FY2012) and Kaiser Permanente Washington (KPW; 1996–2012) health care systems, by metformin initiation status in 6-months after HbA1c index, before inverse probability of treatment weightinga
| VHA (n=112,845) | KPW (n=14,333) | |||||||
|---|---|---|---|---|---|---|---|---|
| Covariates, mean(±sd) or n(%)b | Non-initiators (n=93,941) | MET Initiators (n=18,904) | p-value | SMD %c | Non-initiators (n=12,540) | MET Initiators (n=1,793) | p-value | SMD %c |
| Index year | <.0001 | <.0001 | ||||||
| 1996–1998 | - | - | - | - | 3526 (28.1) | 127 (7.1) | −57.5% | |
| 1999–2000 | - | - | - | - | 1529 (12.2) | 100 (5.6) | −23.4% | |
| 2001–2002 | - | - | - | - | 1323 (10.6) | 134 (7.5) | −10.8% | |
| 2002–2004 | 11591 (12.3) | 1888 (10.0) | −7.5% | - | - | - | ||
| 2003–2004 | - | - | - | 1320 (10.5) | 219 (12.2) | 5.3% | ||
| 2005–2006 | 30475 (32.4) | 5986 (31.7) | −1.7% | 1643 (13.1) | 298 (16.6) | 9.9% | ||
| 2007–2008 | 21953 (23.4) | 4906 (26.0) | 6.0% | 1291 (10.3) | 348 (19.4) | 25.8% | ||
| 2009–2012 | - | - | - | 1908 (15.2) | 567 (31.6) | 39.5% | ||
| 2009–2010 | 18739 (20.0) | 3937 (20.8) | 2.2% | - | - | - | ||
| 2011–2012 | 11183 (11.9) | 2187 (11.6) | −1.0% | - | - | - | ||
| Sociodemographic-related | ||||||||
| Age (y) | 63.2 (±9.1) | 59.5 (±7.8) | <.0001 | −43.5% | 64.3 (±9.9) | 59.9 (±7.8) | <.0001 | −49.0% |
| Age category | ||||||||
| 50–64 y | 51741 (55.1) | 13791 (73.0) | 37.9% | 6896 (55.0) | 1336 (74.5) | 41.7% | ||
| 65–74 y | 29114 (31.0) | 4053 (21.4) | <.0001 | −21.9% | 3360 (26.8) | 351 (19.6) | <.0001 | −17.2% |
| ≥ 75 y | 13086 (13.9) | 1060 (5.6) | −28.3% | 2284 (18.2) | 106 (5.9) | −38.5% | ||
| Male gender | 90990 (96.9) | 18230 (96.4) | .003 | −2.4% | 6093 (48.6) | 878 (49.0) | .764 | 0.8% |
| Race | ||||||||
| White | 76735 (81.7) | 15690 (83.0) | 3.5% | 9229 (73.6) | 1313 (73.2) | −0.8% | ||
| Black | 15336 (16.3) | 2870 (15.2) | .0001 | −3.1% | 616 (4.9) | 79 (4.4) | −2.4% | |
| Asian | - | - | - | 1039 (8.3) | 144 (8.0) | .611 | −0.9% | |
| Other | 1870 (2.0) | 344 (1.8) | −1.3% | 362 (2.9) | 53 (3.0) | 0.4% | ||
| Unknown | - | - | - | 1294 (10.3) | 204 (11.4) | 3.4% | ||
| Married | 57601 (61.3) | 10803 (57.2) | <.0001 | −8.5% | - | - | - | |
| Low nSESd | 46677 (49.7) | 9745 (51.6) | <.0001 | 3.7% | 6116 (48.8) | 949 (52.9) | .001 | 8.3% |
| VHA only insurance | 37858 (40.3) | 9582 (50.7) | <.0001 | 21.0% | - | - | - | |
| Medicaid/Medicare | - | - | - | 5573 (44.4) | 487 (27.2) | <.0001 | −36.6% | |
| High healthcare utilization | 23108 (24.6) | 5103 (27.0) | <.0001 | 5.5% | 3177 (25.3) | 382 (21.3) | .0002 | −9.5% |
| Diabetes-related | ||||||||
| HbA1c value | 6.8 (±0.4) | 7.2 (±0.7) | <.0001 | 72.5% | 7.0 (±0.6) | 7.7 (±0.8) | <.0001 | 97.6% |
| HbA1c category | ||||||||
| 6.5 to < 7.0 | 72042 (76.7) | 8213 (43.5) | −72.2% | 7623 (60.8) | 405 (22.6) | −84.0% | ||
| 7.0 to < 7.5 | 14162 (15.1) | 5042 (26.7) | 28.8% | 2641 (21.1) | 355 (19.8) | −3.1% | ||
| 7.5 to < 8.0 | 4396 (4.7) | 2652 (14.0) | <.0001 | 32.5% | 1163 (9.3) | 325 (18.1) | <.0001 | 26.0% |
| 8.0 to < 8.5 | 1789 (1.9) | 1448 (7.7) | 27.2% | 557 (4.4) | 324 (18.1) | 44.2% | ||
| 8.5 to < 9.0 | 990 (1.1) | 930 (4.9) | 22.9% | 356 (2.8) | 213 (11.9) | 35.2% | ||
| 9.0 to < 9.5 | 562 (0.6) | 619 (3.3) | 19.5% | 200 (1.6) | 171 (9.5) | 35.2% | ||
| Creatinine value | 1.1 (±0.2) | 1.0 (±0.2) | <.0001 | −18.9% | 1.0 (±0.2) | 0.9 (±0.2) | <.0001 | −26.4% |
| Other comorbidities | ||||||||
| Obesity | 47925 (51.0) | 12352 (65.3) | <.0001 | 29.4% | 5313 (42.4) | 1057 (58.9) | <.0001 | 33.6% |
| Hypertension | 84366 (89.8) | 16942 (89.6) | .441 | −0.6% | 6684 (53.3) | 1024 (57.1) | .003 | 7.7% |
| Hyperlipidemia | 80162 (85.3) | 15995 (84.6) | .011 | −2.0% | 3890 (31.0) | 673 (37.5) | <.0001 | 13.8% |
| Stroke | 6232 (6.6) | 1087 (5.8) | <.0001 | −3.7% | 216 (1.7) | 28 (1.6) | .622 | −1.3% |
| Ischemic heart disease | 46389 (49.4) | 8342 (44.1) | <.0001 | −10.5% | 2074 (16.5) | 209 (11.7) | <.0001 | −14.1% |
| Congestive heart failure | 16873 (18.0) | 2721 (14.4) | <.0001 | −9.7% | 803 (6.4) | 56 (3.1) | <.0001 | −15.5% |
| Atrial fibrillation | 14167 (15.1) | 2052 (10.9) | <.0001 | −12.6% | 864 (6.9) | 75 (4.2) | <.0001 | −11.9% |
| Traumatic brain injury | 5053 (5.4) | 1021 (5.4) | .902 | 0.1% | 144 (1.2) | 19 (1.1) | .740 | −0.9% |
| Vitamin B12 deficiency | 4657 (5.0) | 733 (3.9) | <.0001 | −5.3% | 100 (0.8) | 19 (1.1) | .252 | 2.7% |
| Psychiatric and substance comorbidities | ||||||||
| Depression | 21398 (22.8) | 5545 (29.3) | <.0001 | 15.0% | 472 (3.8) | 71 (4.0) | .685 | 1.0% |
| PTSD | 13381 (14.2) | 3817 (20.2) | <.0001 | 15.8% | 32 (0.3) | 9 (0.5) | .067 | 4.0% |
| Other anxietye | 10757 (11.5) | 2496 (13.2) | <.0001 | 5.3% | 287 (2.3) | 50 (2.8) | .191 | 3.2% |
| Bipolar disorder | 5608 (6.0) | 1579 (8.4) | <.0001 | 9.3% | 139 (1.1) | 29 (1.6) | .061 | 4.4% |
| Schizophrenia | 4523 (4.8) | 1139 (6.0) | <.0001 | 5.4% | 25 (0.2) | 6 (0.3) | .249 | 2.6% |
| Nicotine dependence/smoker | 46163 (49.1) | 10251 (54.2) | <.0001 | 10.2% | 1862 (14.8) | 320 (17.8) | .001 | 8.1% |
| Alcohol abuse/dependence | 12432 (13.2) | 3195 (16.9) | <.0001 | 10.3% | 214 (1.7) | 27 (1.5) | .536 | −1.6% |
| Illicit drug abuse/dependence | 6218 (6.6) | 1671 (8.8) | <.0001 | 8.3% | 55 (0.4) | 11 (0.6) | .306 | 2.4% |
| Other medications f | ||||||||
| Statins | 64341 (68.5) | 12880 (68.1) | .335 | −0.8% | 3168 (25.3) | 531 (29.6) | <.0001 | 9.8% |
| Anticholinergic drugs | 37148 (39.5) | 8610 (45.6) | <.0001 | 12.2% | 2776 (22.1) | 394 (22.0) | .876 | −0.4% |
| NSAIDs | 46725 (49.7) | 10971 (58.0) | <.0001 | 16.7% | 2389 (19.1) | 340 (19.0) | .929 | −0.2% |
| Antihypertensive drugs | 81594 (86.9) | 16493 (87.3) | .147 | 1.2% | 7731 (61.6) | 1144 (63.8) | .079 | 4.5% |
FY = fiscal year; MET=metformin; HbA1c = hemoglobin A1c; nSES = neighborhood socioeconomic status; NSAID = nonsteroidal anti-inflammatory drug; PTSD = posttraumatic stress disorder.
VHA measures covariates from start of FY00 to index HbA1c while KPW measures from 2 years prior and up to index HbA1c.
SMD% = standardized mean difference percentage comparing metformin initiation to non-initiation; SMD% >10 was considered a large difference.
low nSES = top 50th percentile of factor score from 7 measures obtained from 2009–2013 5-year census estimates from the American Community Survey.
Other anxiety disorders = panic disorder, obsessive-compulsive disorder, social phobia, generalized anxiety disorder, anxiety
Other medications associated with dementia = sustained use on or before index HbA1c (≥ 2 fills in a 6-mo period).