Table 1.
Baseline characteristics
| Variable | Valproic acid users (n = 4596) | Phenytoin users (n = 8478) | Standardized difference |
|---|---|---|---|
| Age (median, IQR) | 76 (71–82) | 78 (72–83) | 0.12 |
| 66 – 74 | 1971 (42.9%) | 3177 (37.5%) | 0.12 |
| 75 – 84 | 1871 (40.7%) | 3700 (43.6%) | 0.06 |
| 85+ | 754 (16.4%) | 1601 (18.9%) | 0.06 |
| Female, no. (%) | 2480 (54.0%) | 4030 (47.5%) | 0.13 |
| Charlson Co-morbidity Index, No. (%) | |||
| No hospitalization | 2110 (45.9%) | 2998 (35.4%) | 0.22 |
| 0 | 732 (15.9%) | 1101 (13.0%) | 0.08 |
| 1 | 722 (15.7%) | 1465 (17.3%) | 0.04 |
| 2 + | 1032 (22.5%) | 2914 (34.4%) | 0.26 |
| Number of prescription medications in previous year (median, IQR) | 12.0 (8.0–17.0) | 10.0 (6.0–15.0) | 0.29 |
| Residence in a long-term care facility, no. (%) | 1701 (37.0%) | 2417 (28.5%) | 0.18 |
| Medication use in previous 365 days, no. (%) | |||
| Inhaled corticosteroid | 813 (17.7%) | 1453 (17.1%) | 0.01 |
| Inhaled anticholinergic | 621 (13.5%) | 1176 (13.9%) | 0.01 |
| Long-acting bronchodilator | 75 (1.6%) | 94 (1.1%) | 0.05 |
| Short-acting bronchodilator | 1018 (22.2%) | 1984 (23.4%) | 0.03 |
| Inhaled bronchodilator/corticosteroid combination | 338 (7.4%) | 462 (5.5%) | 0.08 |
| Inhaled bronchodilator/anticholinergic combination | 260 (5.7%) | 409 (4.8%) | 0.04 |
| Xanthine | 71 (1.5%) | 330 (3.9%) | 0.14 |
| Respiratory antibiotic | 1756 (38.2%) | 3150 (37.2%) | 0.02 |
| Previous diagnoses | |||
| Myocardial infarction | 363 (7.9%) | 600 (7.1%) | 0.03 |
| Diabetes | 1305 (28.4%) | 2368 (27.9%) | 0.01 |
| Asthma | 1115 (24.3%) | 1900 (22.4%) | 0.04 |
| Congestive heart failure | 1090 (23.7%) | 2284 (26.9%) | 0.07 |
| Medical conditions in previous 2 years | |||
| Aspiration pneumonia | 77 (1.7%) | 195 (2.3%) | 0.04 |
| Pneumonia | 326 (7.1%) | 808 (9.5%) | 0.09 |
| Influenza | 8 (0.2%) | 23 (0.3%) | 0.02 |
| Seizure disorder | 80 (1.7%) | 843 (9.9%) | 0.3 |
| Alcohol abuse | 147 (3.2%) | 465 (5.5%) | 0.11 |
| Pneumothorax | 10 (0.2%) | 17 (0.2%) | 0.00 |
| Stroke or transient ischemic attack | 275 (6.0%) | 1712 (20.2%) | 0.40 |
| Pulmonary embolism | 26 (0.6%) | 53 (0.6%) | 0.01 |
| Lung malignancy | 14 (0.3%) | 138 (1.6%) | 0.12 |
| Income quintile, no. (%) | |||
| 1 (lowest) | 1085 (23.6%) | 2061 (24.3%) | 0.02 |
| 2 | 985 (21.4%) | 1920 (22.7%) | 0.03 |
| 3 | 920 (20.0%) | 1684 (19.9%) | 0.00 |
| 4 | 807 (17.6%) | 1432 (16.9%) | 0.02 |
| 5 (highest) | 782 (17.0%) | 1313 (15.5%) | 0.04 |
| Missing | 17 (0.4%) | 68 (0.8%) | 0.05 |