| Characteristic | Adjusted OR (99% CI)* |
|---|---|
| Patient | |
| Age, yr | |
| 18–35 | Ref |
| 36–50 | 0.92 (0.81–1.05) |
| 51–65 | 0.69 (0.61–0.79) |
| 66–80 | 0.46 (0.40–0.53) |
| > 80 | 0.21 (0.18–0.25) |
| Male sex | 0.87 (0.80–0.95) |
| Income quintile | |
| 1 (lowest) | Ref |
| 2 | 0.98 (0.87–1.10) |
| 3 | 0.93 (0.82–1.05) |
| 4 | 1.06 (0.94–1.21) |
| 5 | 1.12 (0.98–1.27) |
| Comorbidity index quartile | |
| 1 (lowest) | Ref |
| 2 | 0.90 (0.80–1.01) |
| 3 | 0.89 (0.79–1.00) |
| 4 | 0.67 (0.60–0.75) |
| Common bile duct obstruction | 0.41 (0.36–0.47) |
| Pancreatitis | 1.14 (0.94–1.37) |
| Hospital | |
| Annual volume of acute cholecystitis admissions (quartile) | |
| 5–17 | 0.53 (0.35–0.78) |
| 18–39 | 0.67 (0.52–0.87) |
| 40–65 | 0.84 (0.72–0.97) |
| 66–164 | Ref |
| After-hours operating room use† (quartile) | |
| 1 (lowest) | 0.97 (0.72–1.30) |
| 2 | 0.84 (0.66–1.07) |
| 3 | 0.79 (0.64–0.97) |
| 4 | Ref |
| Annual volume of elective cholecystectomies (quartile) | |
| 0–74 | 1.02 (0.63–1.63) |
| 75–159 | 1.15 (0.82–1.60) |
| 160–279 | 1.11 (0.91–1.35) |
| 280–905 | Ref |
| Academic teaching hospital | 0.71 (0.27–1.85) |
Note: CI = confidence interval, OR = odds ratio, Ref = reference. *All listed covariates were included in a multivariable model that also accounted for the nonindependence of patients admitted to the same hospital. †Ratio of total after-hours operative cases (for all surgical specialties) divided by the number of all-cause emergency department visits.