| A. Results for 1-Year Cost Analysis | ||||||
| Cost Category | Inpatient Costs | Outpatient Costs | ER Costs | DM Drug Costs | Other Costs | Total Costs |
| Distribution Assumption | ZINB Model | Gamma Model | ZINB Model | Gamma Model | Gamma Model | Gamma Model |
| Variable | Estimates | |||||
| Intercept | 11.0676 | 7.9768 | 6.6008 | 4.8953 | 7.1932 | 9.0216 |
| Sex (reference: male) | ||||||
| Female | -0.1337 | 0.0375 | 0.0594 | -0.1102 | 0.0339 | NS |
| Male | 0 | 0 | 0 | 0 | 0 | NS |
| Age (reference: 18-39 years) | ||||||
| 40-49 years | 0.2808 | 0.1776 | 0.1098 | -0.0518 | 0.1073 | 0.0966 |
| 49-64 years | 0.4309 | 0.3484 | 0.0911 | -0.0334 | 0.3081 | 0.3338 |
| ≥ 65 years | 0.1297 | 0.2699 | 0.7548 | -0.4867 | 0.2213 | 0.3385 |
| 18-39 years | 0 | 0 | 0 | 0 | 0 | 0 |
| Geographic location (reference: Northeast) | ||||||
| Midwest | -0.0665 | 0.0778 | 0.1661 | -0.0181 | -0.1829 | -0.0667 |
| South | -0.1823 | 0.1015 | 0.1202 | -0.0372 | -0.0561 | -0.1112 |
| West | -0.8922 | -0.0612 | -0.1325 | -0.074 | -0.0258 | -0.3796 |
| Unknown | -2.2988 | -0.1308 | -0.526 | -0.0972 | 0.1237 | -0.6855 |
| Northeast | 0 | 0 | 0 | 0 | 0 | 0 |
| Comorbidity (reference: no comorbidity) | ||||||
| Vascular disease: Yes | 0.217 | 0.3751 | 0.3647 | NS | 0.3192 | 0.4954 |
| Vascular disease: No | 0 | 0 | 0 | NS | 0 | 0 |
| Chronic pulmonary disease: Yes | 0.1173 | 0.2404 | 0.3227 | NS | 0.4137 | 0.3814 |
| Chronic pulmonary disease: No | 0 | 0 | 0 | NS | 0 | 0 |
| Connective tissue disease, rheumatic disease: Yes | NS | 0.4016 | 0.1282 | -0.0774 | 0.5208 | 0.3508 |
| Connective tissue disease, rheumatic disease: No | NS | 0 | 0 | 0 | 0 | 0 |
| Peptic ulcer: Yes | 0.2155 | NS | NS | NS | NS | NS |
| Peptic ulcer: No | 0 | NS | NS | NS | NS | NS |
| Mild liver disease: Yes | 0.1164 | 0.3916 | 0.1252 | NS | 0.2252 | 0.2639 |
| Mild liver disease: No | 0 | 0 | 0 | NS | 0 | 0 |
| Renal disease: Yes | NS | 0.5179 | 0.0923 | 0.1834 | 0.2457 | 0.3834 |
| Renal disease: No | NS | 0 | 0 | 0 | 0 | 0 |
| Moderate or severe liver disease: Yes | NS | NS | NS | NS | 0.5492 | 0.4724 |
| Moderate or severe liver disease: No | NS | NS | NS | NS | 0 | 0 |
| Hypertension: Yes | NS | 0.1362 | 0.2203 | 0.0512 | 0.0997 | 0.1319 |
| Hypertension: No | NS | 0 | 0 | 0 | 0 | 0 |
| Hyperlipidemia: Yes | NS | NS | NS | 0.1057 | NS | NS |
| Hyperlipidemia: No | NS | NS | NS | 0 | NS | NS |
| Obesity: Yes | NS | 0.148 | 0.1039 | 0.1142 | 0.066 | 0.1219 |
| Obesity: No | NS | 0 | 0 | 0 | 0 | 0 |
| Gastrointestinal disease: Yes | 0.0868 | 0.3789 | 0.2805 | -0.0257 | 0.2075 | 0.3584 |
| Gastrointestinal disease: No | 0 | 0 | 0 | 0 | 0 | 0 |
| Pancreatitis: Yes | 0.3637 | 0.1981 | 0.1776 | NS | 0.1846 | 0.4717 |
| Pancreatitis: No | 0 | 0 | 0 | NS | 0 | 0 |
| Foot disease: Yes | 0.1924 | 0.3608 | 0.1699 | 0.0783 | 0.2163 | 0.3887 |
| Foot disease: No | 0 | 0 | 0 | 0 | 0 | 0 |
| Neuropathy: Yes | NS | 0.1346 | 0.1317 | 0.1665 | 0.1888 | 0.1854 |
| Neuropathy: No | NS | 0 | 0 | 0 | 0 | 0 |
| Retinopathy: Yes | 0.0601 | 0.2053 | NS | 0.2784 | 0.109 | 0.1177 |
| Retinopathy: No | 0 | 0 | NS | 0 | 0 | 0 |
| Endocrinologist visit (reference: no endocrinologist visit) | ||||||
| Yes | NS | 0.2316 | NS | 0.6146 | 0.2982 | 0.2239 |
| No | NS | 0 | NS | 0 | 0 | 0 |
| Adherencea | -0.032 | -0.055 | -0.0335 | 0.4652 | 0.1229 | 0.0141 |
| Hypoglycemia (Reference: no hypoglycemia) | ||||||
| Nonhospitalized/ER hypoglycemia | 0.2038 | 0.2682 | 0.1179 | 0.1737 | 0.176 | 0.2878 |
| Hospitalized/ER hypoglycemia | 0.2845 | 0.267 | 0.5136 | 0.0989 | 0.2189 | 0.4665 |
| No hypoglycemia | 0 | 0 | 0 | 0 | 0 | 0 |
| A1c level (reference: ≤ 7%) | ||||||
| 7%-8% | 0.0832 | -0.0095 | 0.0603 | 0.3732 | -0.1213 | 0.0588 |
| 8%-9% | -0.0607 | -0.0423 | -0.0303 | 0.7333 | -0.145 | 0.0565 |
| < 9% | 0.0536 | -0.1207 | 0.2325 | 0.8383 | -0.2075 | 0.1187 |
| ≤ 7% | 0 | 0 | 0 | 0 | 0 | 0 |
| B. Results for 3-Year Cost Analysis | ||||||
| Cost Category | Inpatient Costs | Outpatient Costs | ER Costs | DM Drug Costs | Other Costs | Total Costs |
| Distribution Assumption | ZINB Model | Gamma Model | ZINB Model | Gamma Model | Gamma Model | Gamma Model |
| Variable | Estimates | |||||
| Intercept | 10.4881 | 8.0584 | 6.0139 | 5.0883 | 7.217 | 9.1081 |
| Sex (reference: male) | ||||||
| Female | -0.1304 | NS | 0.0904 | -0.1096 | 0.0212 | NS |
| Male | 0 | NS | 0 | 0 | 0 | NS |
| Age (reference: 18-39 years) | ||||||
| 40-49 years | 0.1707 | 0.2156 | 0.1334 | -0.0458 | 0.1298 | 0.1102 |
| 49-64 years | 0.3747 | 0.3921 | 0.2073 | -0.0448 | 0.3197 | 0.3706 |
| ≥ 65 years | 0.0755 | 0.3029 | 0.814 | -0.5418 | 0.2705 | 0.4148 |
| 18-39 years | 0 | 0 | 0 | 0 | 0 | 0 |
| Geographic location (reference: Northeast) | ||||||
| Midwest | -0.0433 | 0.0985 | 0.1373 | -0.0001 | -0.1544 | -0.0435 |
| South | -0.1911 | 0.1154 | 0.0723 | -0.0387 | -0.0253 | -0.1088 |
| West | -0.9283 | -0.0959 | -0.2351 | -0.1017 | 0.0597 | -0.4 |
| Unknown | -2.3012 | -0.1897 | -0.5066 | -0.1115 | 0.1646 | -0.7714 |
| Northeast | 0 | 0 | 0 | 0 | 0 | 0 |
| Comorbidity (reference: no comorbidity) | ||||||
| Vascular disease: Yes | 0.2976 | 0.343 | 0.4431 | NS | 0.2869 | 0.473 |
| Vascular disease: No | 0 | 0 | 0 | NS | 0 | 0 |
| Chronic pulmonary disease: Yes | 0.1807 | 0.2318 | 0.3642 | NS | 0.3933 | 0.3574 |
| Chronic pulmonary disease: No | 0 | 0 | 0 | NS | 0 | 0 |
| Connective tissue disease, rheumatic disease: Yes | 0.1282 | 0.374 | 0.1514 | -0.0785 | 0.5274 | 0.3495 |
| Connective tissue disease, rheumatic disease: No | 0 | 0 | 0 | 0 | 0 | 0 |
| Peptic ulcer: Yes | 0.1915 | NS | NS | NS | 0.1081 | 0.126 |
| Peptic ulcer: No | 0 | NS | NS | NS | 0 | 0 |
| Mild liver disease: Yes | 0.1208 | 0.3141 | 0.1671 | NS | 0.2201 | 0.2386 |
| Mild liver disease: No | 0 | 0 | 0 | NS | 0 | 0 |
| Renal disease: Yes | 0.1139 | 0.5776 | 0.1156 | 0.1646 | 0.2522 | 0.4002 |
| Renal disease: No | 0 | 0 | 0 | 0 | 0 | 0 |
| Moderate or severe liver disease: Yes | 0.3707 | 0.2196 | NS | NS | 0.5293 | 0.5622 |
| Moderate or severe liver disease: No | 0 | 0 | NS | NS | 0 | 0 |
| Hypertension: Yes | NS | 0.1284 | 0.2553 | 0.0491 | 0.0833 | 0.1551 |
| Hypertension: No | NS | 0 | 0 | 0 | 0 | 0 |
| Hyperlipidemia: Yes | NS | NS | NS | 0.1227 | NS | -0.0246 |
| Hyperlipidemia: No | NS | NS | NS | 0 | NS | 0 |
| Obesity: Yes | 0.0608 | 0.1287 | 0.0927 | 0.122 | 0.0583 | 0.108 |
| Obesity: No | 0 | 0 | 0 | 0 | 0 | 0 |
| Gastrointestinal disease: Yes | 0.157 | 0.3228 | 0.3267 | NS | 0.1872 | 0.303 |
| Comorbidity (reference: no comorbidity) | ||||||
| Gastrointestinal disease: No | 0 | 0 | 0 | NS | 0 | 0 |
| Pancreatitis: Yes | 0.3482 | 0.1773 | 0.2406 | NS | 0.1612 | 0.4011 |
| Pancreatitis: No | 0 | 0 | 0 | NS | 0 | 0 |
| Foot disease: Yes | 0.238 | 0.3229 | 0.2327 | 0.084 | 0.2031 | 0.3664 |
| Foot disease: No | 0 | 0 | 0 | 0 | 0 | 0 |
| Neuropathy: Yes | NS | 0.1412 | 0.1722 | 0.1676 | 0.1954 | 0.1954 |
| Neuropathy: No | NS | 0 | 0 | 0 | 0 | 0 |
| Retinopathy: Yes | 0.0831 | 0.2358 | NS | 0.2668 | 0.1114 | 0.1506 |
| Retinopathy: No | 0 | 0 | NS | 0 | 0 | 0 |
| Endocrinologist visit (reference: no endocrinologist visit) | ||||||
| Yes | NS | 0.1918 | -0.0787 | 0.6071 | 0.291 | 0.1929 |
| No | NS | 0 | 0 | 0 | 0 | 0 |
| Adherence | -0.0459 | -0.0623 | -0.0492 | 0.4165 | 0.1087 | NS |
| Hypoglycemia (reference: no hypoglycemia) | ||||||
| Nonhospitalized/ER hypoglycemia | 0.2139 | 0.2598 | 0.1157 | 0.1517 | 0.1608 | 0.2706 |
| Hospitalized/ER hypoglycemia | 0.4011 | 0.3136 | 0.7325 | 0.1 | 0.2336 | 0.4563 |
| No hypoglycemia | 0 | 0 | 0 | 0 | 0 | 0 |
| A1c level (reference: ≤ 7%) | ||||||
| 7%-8% | 0.1401 | NS | 0.1219 | 0.4022 | -0.1015 | 0.086 |
| 8%-9% | 0.026 | NS | 0.019 | 0.7735 | -0.1054 | 0.0908 |
| < 9% | 0.1808 | NS | 0.2207 | 0.871 | -0.1833 | 0.1831 |
| ≤ 7% | 0 | NS | 0 | 0 | 0 | 0 |
Note: NS is not significant. These variables are not significant predictors of costs in the variable selection process (using a threshold of P<0.1) and therefore are not included in the cost equation.
aAdherence was defined as an ordinal variable but was considered as a continuous variable, since a linear relationship with cost variables was observed.
A1c = hemoglobin; DM = diabetes mellitus; ER = emergency room; ZINB = zero-inflated negative binomial.