Table 1. Baseline Characteristics of Patients in the Surgical Group vs Control Group.
| Variable | Original cohort before COVID-19 outbreak (N = 20 212)a | At-risk cohort after COVID-19 outbreak (n = 11 809)b | ||||
|---|---|---|---|---|---|---|
| Surgical group, No. (%) | Control group, No. (%) | Standardized mean difference, %c | Surgical group, No. (%) | Control group, No. (%) | Standardized mean difference, %c | |
| All patients | 5053 (25.0) | 15 159 (75.0) | NA | 2958 (25.0) | 8851 (75.0) | NA |
| Index year, median (IQR) | 2013 (2010 to 2015) | 2013 (2010 to 2015) | 0.5 | 2013 (2011 to 2016) | 2013 (2011 to 2016) | 0.4 |
| Age, median (IQR), y | 46.0 (37.0 to 55.0) | 46.0 (34.0 to 57.0) | 1.5 | 46.0 (38.0 to 55.0) | 46.0 (34.0 to 56.0) | 5.3 |
| Sex | ||||||
| Female | 3884 (76.9) | 11 806 (77.9) | 2.4 | 2325 (78.6) | 6950 (78.5) | 0.2 |
| Male | 1169 (23.1) | 3353 (22.1) | 2.4 | 633 (21.4) | 1901 (21.5) | 0.2 |
| BMI, median (IQR) | 45.5 (41.0 to 51.6) | 45.3 (40.8 to 50.9) | 6.5 | 45.4 (40.9 to 51.4) | 45.3 (40.8 to 50.7) | 5.6 |
| BMI category | ||||||
| 35-39.9 | 1005 (19.9) | 2839 (18.7) | 2.9 | 606 (20.5) | 1654 (18.7) | 4.5 |
| 40-44.9 | 1372 (27.2) | 4410 (29.1) | 4.3 | 817 (27.6) | 2616 (29.6) | 4.3 |
| 45-49.9 | 1150 (22.8) | 3586 (23.7) | 2.1 | 663 (22.4) | 2099 (23.7) | 3.1 |
| 50-54.9 | 743 (14.7) | 2213 (14.6) | 0.3 | 434 (14.7) | 1319 (14.9) | 0.6 |
| 55-59.9 | 393 (7.8) | 1074 (7.1) | 2.6 | 230 (7.8) | 602 (6.8) | 3.7 |
| 60-80 | 390 (7.7) | 1037 (6.8) | 3.4 | 208 (7.0) | 561 (6.3) | 2.8 |
| Race and ethnicityd | ||||||
| Black | 1153 (22.8) | 3428 (22.6) | 0.5 | 780 (26.4) | 2059 (23.3) | 7.2 |
| White | 3724 (73.7) | 11 196 (73.9) | 0.4 | 2068 (69.9) | 6484 (73.3) | 7.4 |
| Othere | 176 (3.5) | 535 (3.5) | 0.3 | 110 (3.7) | 308 (3.5) | 1.3 |
| State of residence | ||||||
| Ohio | 3997 (79.1) | 12 397 (81.8) | 6.8 | 2578 (87.2) | 7645 (86.4) | 2.3 |
| Florida | 829 (16.4) | 2109 (13.9) | 7.0 | 326 (11.0) | 991 (11.2) | 0.6 |
| Other US states | 227 (4.5) | 653 (4.3) | 0.9 | 54 (1.8) | 215 (2.4) | 4.2 |
| Smoking status | ||||||
| Never | 3019 (59.7) | 9322 (61.5) | 3.6 | 1760 (59.5) | 5500 (62.1) | 5.4 |
| Former | 1889 (37.4) | 5498 (36.3) | 2.3 | 1126 (38.1) | 3170 (35.8) | 4.7 |
| Current | 145 (2.9) | 339 (2.2) | 4.0 | 72 (2.4) | 181 (2.0) | 2.6 |
| Annual income within zip code, median (IQR), $ | 51 962 (42 613 to 67 184) | 50 642 (39 814 to 66 468) | 7.0 | 51 962 (40 664 to 69 434) | 51 089 (39 850 to 67 717) | 4.6 |
| Missing data | 88 (1.7) | 171 (1.1) | NA | 24 (0.8) | 69 (0.8) | NA |
| Charlson Comorbidity Index score, median (IQR)f | 2.0 (1.0 to 3.0) | 1.0 (0 to 3.0) | 14.6 | 2.0 (1.0 to 3.0) | 2.0 (0 to 3.0) | 12.8 |
| Elixhauser Comorbidity Index score, median (IQR)g | 1.0 (−4.0 to 8.0) | 0 (−2.0 to 4.0) | 9.3 | 3.0 (−4.0 to 9.0) | 0 (−2.0 to 5.0) | 17.5 |
| eGFR, median (IQR), mL/minh | 104 (86.2 to 122) | 92.3 (74.5 to 111) | 37.2 | 104 (86.2 to 121) | 93.2 (76.0 to 112) | 32.7 |
| Missing data | 0 | 3249 (21.4) | NA | 0 | 1567 (17.7) | NA |
| Diabetes medication use | 1789 (35.4) | 4708 (31.1) | 9.2 | 1071 (36.2) | 3063 (34.6) | 3.3 |
| Antihypertensive medication use | 4283 (84.8) | 7685 (50.7) | 78.2 | 2527 (85.4) | 4823 (54.5) | 71.7 |
| Lipid-lowering medication use | 1817 (36.0) | 4530 (29.9) | 13.0 | 1086 (36.7) | 2882 (32.6) | 8.7 |
| Aspirin use | 1164 (23.0) | 3032 (20.0) | 7.4 | 744 (25.2) | 1891 (21.4) | 9.0 |
| Follow-up time, median (IQR), y | 5.9 (3.4 to 9.0) | 6.2 (3.9 to 9.0) | 7.7 | 7.5 (5.1 to 10.4) | 7.6 (5.2 to 10.2) | 0.8 |
Abbreviations: BMI, body mass index; eGFR, estimated glomerular filtration rate; NA, not applicable.
Baseline characteristics of patients in the original cohort (5053 in the surgical group and 15 159 in the control group) were well balanced with matching.
Baseline characteristics of patients who were at risk for COVID-19 infection between March 1, 2020, and March 1, 2021 (2958 in the surgical group and 8851 in the control group), were largely balanced. For the few remaining variables, the surgical group had a higher baseline profile (eg, higher rate of antihypertensive medication use and comorbidity scores). All baseline variables were included in the fully adjusted Cox proportional hazards regression models. The intention of the regression adjustment was to be the main method of actual statistical adjustment for comparison of study groups to control any imbalances that remained after the matching process.
Standardized mean differences (%) are the absolute value of the difference in means or proportions between the surgical group and control group divided by pooled SD. Values of 10% or less indicate appropriate matching.
Race and ethnicity were obtained from electronic health records and based on patients selecting from fixed categories.
Other category included American Indian or Alaska Native, Asian, Native Hawaiian or Other Pacific Islander, and multiracial.
Charlson Comorbidity Index score range: 0 to 29, with the highest score indicating maximal disease burden and predicting the risk of death.
Elixhauser Comorbidity Index with van Walraven weights score range: –19 to 89, with the highest score indicating greater comorbidity burden and greater likelihood for in-hospital death.
eGFR was approximated using the Modification of Diet in Renal Disease study equation.