Table 1
Covariates available for analysis, their values in each group, and the impact of propensity score weighting on the differences seen in means and variances.
| CIH code group (n = 30,634) | Control group before weighting (n = 195,424) | p-value | Standardized Difference | Var† ratio | ||
|---|---|---|---|---|---|---|
| Raw | Wtd* | Wtd* | ||||
| Demographics | ||||||
| Female (Ref: Male) | 7,360 (24.0%) | 31,934 (16.3%) | < .001 | 0.192 | 0.003 | 1.004 |
| Age (Ref: 18–34 years) | ||||||
| Age 35–44 years | 10,148 (33.1%) | 62,260 (31.9%) | < .001 | 0.027 | 0.001 | 1.001 |
| Age 45–54 years | 10,738 (35.1%) | 80,105 (41.0%) | < .001 | -0.123 | -0.002 | 0.999 |
| Race/Ethnicity (Ref: Non-Hispanic White) | ||||||
| Non-Hispanic Black | 6,377 (20.8%) | 51,011 (26.1%) | < .001 | -0.125 | 0.010 | 1.015 |
| Hispanic or Latino | 4,364 (14.3%) | 15,471 (7.9%) | < .001 | 0.203 | 0.001 | 1.002 |
| Non-Hispanic Other | 1,332 (4.4%) | 6,613 (3.4%) | < .001 | 0.050 | -0.002 | 0.992 |
| Marital status (Ref: Married) | ||||||
| Single/Never married | 7,500 (24.5%) | 42,815 (21.9%) | < .001 | 0.061 | 0.003 | 1.004 |
| Divorced/Separated/Widowed | 9,008 (29.4%) | 55,939 (28.6%) | 0.005 | 0.017 | -0.004 | 0.997 |
| Missing marital | 66 (0.2%) | 524 (0.3%) | 0.093 | -0.011 | 0.001 | 1.013 |
| Veteran status and interaction with the VA healthcare system | ||||||
| Financial means test (Ref: Copay exempt) | ||||||
| Copay required | 2,183 (7.1%) | 21,157 (10.8%) | < .001 | -0.130 | -0.001 | 0.995 |
| Other financial means test | 877 (2.9%) | 8,434 (4.3%) | < .001 | -0.078 | 0.002 | 1.011 |
| Health insurance status (Ref: VA coverage only) | ||||||
| Private insurance | 6,080 (19.9%) | 45,586 (23.3%) | < .001 | -0.085 | 0.006 | 1.009 |
| Non-VA government insurance | 5,831 (19.0%) | 28,685 (14.7%) | < .001 | 0.117 | -0.005 | 0.992 |
| Eligibility for VA benefits (Ref: Priority group 1) | ||||||
| Priority group 2–6‡ | 15,409 (50.3%) | 114,162 (58.4%) | < .001 | -0.164 | 0.005 | 1.000 |
| Priority group 7–8‡ | 1,093 (3.6%) | 13,181 (6.7%) | < .001 | -0.144 | -0.003 | 0.985 |
| Missing priority group | 85 (0.3%) | 458 (0.2%) | 0.152 | 0.009 | -0.001 | 0.988 |
| Whether disability connected to military service (Ref: Service connectedness <50%) | ||||||
| Service connectedness ≥50%§ | 16,250 (53.1%) | 77,557 (39.7%) | < .001 | 0.270 | -0.002 | 1.000 |
| Missing service connectedness§ | 3,418 (11.2%) | 38,135 (19.5%) | < .001 | -0.233 | -0.005 | 0.988 |
| Pain-related comorbidities | ||||||
| Anxiety | 8,646 (28.2%) | 37,831 (19.4%) | < .001 | 0.209 | -0.001 | 0.999 |
| Depression | 16,724 (54.6%) | 74,534 (38.1%) | < .001 | 0.335 | -0.001 | 1.000 |
| Post-traumatic stress disorder | 13,862 (45.3%) | 58,147 (29.8%) | < .001 | 0.324 | 0.004 | 1.001 |
| Traumatic brain injury | 4,416 (14.4%) | 13,767 (7.0%) | < .001 | 0.240 | -0.001 | 0.997 |
| Substance abuse | 13,384 (43.7%) | 80,137 (41.0%) | < .001 | 0.054 | -0.006 | 0.998 |
| Sleep disturbance | 9,196 (30.0%) | 47,343 (24.2%) | < .001 | 0.131 | -0.001 | 0.999 |
| Types of musculoskeletal disorders | ||||||
| Back pain | 17,859 (58.3%) | 97,441 (49.9%) | < .001 | 0.170 | -0.007 | 1.002 |
| Neck pain | 6,855 (22.4%) | 29,710 (15.2%) | < .001 | 0.184 | -0.009 | 0.988 |
| Joint pain | 9,243 (30.2%) | 79,249 (40.6%) | < .001 | -0.218 | 0.012 | 1.011 |
| Osteoarthritis | 2,180 (7.1%) | 16,661 (8.5%) | < .001 | -0.053 | -0.002 | 0.994 |
| Temporomandibular joint disorder | 236 (0.8%) | 863 (0.4%) | < .001 | 0.042 | 0.001 | 1.010 |
| Fibromyalgia | 2,461 (8.0%) | 13,227 (6.8%) | < .001 | 0.048 | 0.007 | 1.021 |
| General comorbidities | ||||||
| Human immunodeficiency virus | 204 (0.7%) | 1,301 (0.7%) | < .001 | 0.001 | -0.001 | 0.990 |
| Cancer | 3,713 (12.1%) | 18,367 (9.4%) | < .001 | 0.088 | -0.003 | 0.992 |
| Diabetes | 4,909 (16.0%) | 35,296 (18.1%) | < .001 | -0.054 | -0.001 | 0.999 |
| Obesity | 12,403 (40.5%) | 73,397 (37.6%) | < .001 | 0.060 | 0.005 | 1.001 |
| Headache | 13,370 (43.6%) | 60,205 (30.8%) | < .001 | 0.268 | -0.002 | 0.999 |
| Hypertension | 10,724 (35.0%) | 75,358 (38.6%) | < .001 | -0.074 | 0.000 | 1.000 |
| Heart disease | 10,493 (34.3%) | 59,083 (30.2%) | < .001 | 0.087 | -0.006 | 0.996 |
| Cerebrovascular | 867 (2.8%) | 4,553 (2.3%) | < .001 | 0.032 | -0.000 | 0.999 |
| Chronic obstructive pulmonary disease | 4,393 (14.3%) | 24,213 (12.4%) | < .001 | 0.057 | -0.007 | 0.986 |
| Asthma | 3,522 (11.5%) | 17,974 (9.2%) | < .001 | 0.076 | -0.003 | 0.993 |
| Mental illness | 26,873 (87.7%) | 157,388 (80.5%) | < .001 | 0.198 | 0.001 | 0.998 |
| Charlson index‖ | 4,893 (16.0%) | 30,394 (15.6%) | 0.060 | 0.012 | -0.005 | 0.991 |
| Year-before the start date values for each outcome | ||||||
| Annual healthcare cost | $10,729 ($9,562) | $5,818 ($6,589) | < .001 | 0.598 | -0.070 | 0.639 |
| Time-weighted pain score | 4.33 (2.3) | 3.76 (2.6) | < .001 | 0.232 | -0.005 | 0.887 |
| Opioid use | 20,408 (66.6%) | 105,516 (54.0%) | < .001 | 0.268 | -0.012 | 1.009 |
†Variance ratio = ratio of the variances seen in each group. Ideally, after weighting this number should be near 1.0.
‡Eligibility priority group based on a Veteran’s service, service-related disability, honors, and income: priority group 1 (highest), priority group 2–6, priority group 7–8.
§Service connected disability was incurred or aggravated during active military service. The percentage relates to the level of disability incurred.
‖Based on Quan H, Sundararajan V, Halfon P, et al. Coding algorithms for defining comorbidities in ICD-9-CM and ICD-10 administrative data. Med Care. 2005: 1130–39.