Table 4.
Cox Proportional Hazards Model Estimating the Hazard of Cataract Surgerya
| Covariate | HR (95% CI) | P Value |
|---|---|---|
| Race | ||
| White | 1 [Reference] | |
| Black | 0.85 (0.83–0.87) | <.001 |
| Latino | 1.08 (1.05–1.10) | <.001 |
| Asian | 1.09 (1.05–1.12) | <.001 |
| Other | 1.04 (0.99–1.10) | .01 |
| Income, $ | ||
| <30 000 | 1 [Reference] | |
| 30 000 to <60 000 | 0.99 (0.98–1.01) | .35 |
| 60 000 to <100 000 | 0.94 (0.93–0.96) | <.001 |
| 100 000 to <125 000 | 0.90 (0.88–0.92) | <.001 |
| ≥125 000 | 0.84 (0.82–0.87) | <.001 |
| Education | ||
| <High school | 1 [Reference] | |
| High school diploma | 0.91 (0.88–0.95) | <.001 |
| Some college | 0.83 (0.80–0.86) | <.001 |
| College diploma | 0.76 (0.73–0.79) | <.001 |
| Advanced degree | 0.69 (0.61–0.78) | <.001 |
| Diabetesb | ||
| None | 1 [Reference] | |
| Uncomplicated | 0.94 (0.93–0.95) | <.001 |
| Complicated | 0.95 (0.93–0.96) | <.001 |
| Urban vs rural status | ||
| Urban | 1 [Reference] | |
| Large rural | 1.07 (1.05–1.09) | <.001 |
| Small rural | 1.05 (1.03–1.07) | <.001 |
| Age at cataract diagnosis | 1.02 (1.02–1.03) | <.001 |
| Eye trauma | 1.30 (1.26–1.34) | <.001 |
| Charlson Comorbidity index | 1.01 (1.01-1.01) | <.001 |
| Latitude | 0.99 (0.98–0.99) | <.001 |
| PE GPCI | 0.40 (0.38–0.43) | <.001 |
| Average time in plan | 1.00 (1.00-1.00) | <.001 |
| No. of optometrists per 100 000 population | 1.00 (1.00-1.00) | <.001 |
Abbreviations: ACGME, Accreditation Counsel for Graduate Medical Education; HR, hazard ratio; PE PGCI, Practice Expense–Geographic Practice Cost Index.
Community-level covariates that were considered but not selected as part of the best subset include cost of living index, number of ophthalmologists per 100 000 population, number of physicians per 100 000 population, proportion of population driving to work, longitude, median total charges per patient, number of days of sunshine, UV index, and ACGME Ophthalmology Residency. Patient-level covariates that were considered but not selected as part of the best subset include sex, dementia, and depression.
Uncomplicated diabetes refers to diabetes with no record of end-organ damage from this condition. Complicated diabetes refers to diabetes with a record of end-organ damage (eg, nephropathy).