Table 1.
Baseline characteristics by visit frequency
| Characteristics | All n (%) | Exposure Variable (Mean Number of Monthly Visits to Incident Patients During Run-In) | Instrumental Variable (Mean Number of Monthly Visits to Prevalent Patients) | ||||
|---|---|---|---|---|---|---|---|
| <4 | ≥4 | Absolute Difference | <3.7 | ≥3.7 | Absolute Difference | ||
| All | 130,892 (100) | ||||||
| Age (years) | |||||||
| 20–44 | 11,566 (8.8) | 9.3 | 8.5 | 0.8 | 8.9 | 8.8 | 0.1 |
| 45–64 | 37,535 (28.7) | 29.3 | 28.3 | 1.0 | 29.0 | 28.4 | 0.6 |
| 65–74 | 38,708 (29.6) | 29.4 | 29.7 | −0.3 | 29.6 | 29.6 | 0.0 |
| ≥75 | 43,083 (32.9) | 32.0 | 33.5 | −1.5 | 32.6 | 33.3 | −0.7 |
| Women | 61,038 (46.6) | 46.4 | 46.8 | −0.4 | 46.8 | 46.5 | 0.3 |
| Race | |||||||
| white | 84,723 (64.7) | 65.9 | 64.0 | 1.9 | 65.2 | 64.2 | 1.0 |
| African-American | 40,273 (30.8) | 28.8 | 32.1 | −3.3 | 29.6 | 32.0 | −2.4 |
| other | 5896 (4.5) | 5.3 | 4.0 | 1.3 | 5.1 | 3.8 | 1.3 |
| Hispanic | 14,838 (11.3) | 11.5 | 11.3 | 0.2 | 11.4 | 11.3 | 0.1 |
| Primary cause of ESRD | |||||||
| diabetes | 63,484 (48.5) | 47.9 | 48.9 | −1.0 | 48.4 | 48.6 | −0.2 |
| hypertension | 40,607 (31.0) | 30.9 | 31.1 | −0.2 | 31.1 | 31.0 | 0.1 |
| glomerulonephritis | 7514 (5.7) | 5.9 | 5.6 | 0.3 | 5.7 | 5.7 | 0.0 |
| other | 19,287 (14.7) | 15.3 | 14.4 | 0.9 | 14.8 | 14.7 | 0.1 |
| dual eligibilitya | 51,569 (39.4) | 39.3 | 39.5 | −0.2 | 39.2 | 39.6 | −0.4 |
| Comorbidity score | |||||||
| ≤4 | 50,248 (38.4) | 40.9 | 36.7 | 4.2 | 39.0 | 37.8 | 0.02 |
| >4 to ≤8 | 40,975 (31.3) | 31.0 | 31.5 | −0.5 | 31.0 | 31.7 | −0.01 |
| ≥8 | 39,669 (30.3) | 28.1 | 31.8 | −3.7 | 30.1 | 30.6 | −0.01 |
| Comorbid conditions | |||||||
| ASHD | 65,170 (49.8) | 47.8 | 51.1 | −3.3 | 49.5 | 50.1 | −0.6 |
| CHF | 72,212 (55.2) | 53.3 | 56.4 | −3.1 | 54.9 | 55.4 | −0.5 |
| CVA/TIA | 26,704 (20.4) | 19.4 | 21.1 | −1.7 | 20.3 | 20.5 | −0.2 |
| PVD | 48,663 (37.2) | 35.3 | 38.5 | −3.2 | 36.5 | 37.9 | −1.4 |
| Other cardiac | 41,098 (31.4) | 30.2 | 32.2 | −2.0 | 31.6 | 31.2 | 0.4 |
| COPD | 29,697 (22.7) | 21.8 | 23.3 | −1.5 | 22.8 | 22.6 | 0.2 |
| GI bleeding | 9575 (7.3) | 6.9 | 7.6 | −0.7 | 7.3 | 7.4 | −0.1 |
| Liver disease | 11,209 (8.6) | 7.5 | 9.3 | −1.8 | 7.7 | 9.5 | −1.8 |
| Dysrhythmia | 36,722 (28.1) | 26.9 | 28.8 | −1.9 | 28.3 | 27.8 | 0.5 |
| Cancer | 15,161 (11.6) | 11.1 | 11.9 | −0.8 | 11.3 | 11.9 | −0.7 |
| Diabetes | 89,481 (68.4) | 67.4 | 69.0 | −1.6 | 68.3 | 68.5 | 0.2 |
| SES principle component < medianb | 63,001 (48.1) | 49.0 | 47.5 | 1.5 | 49.0 | 47.3 | 1.7 |
| Urban | 93,012 (71.1) | 67.6 | 73.4 | −5.8 | 69.6 | 72.6 | −3.0 |
| Dialysis sessions during run-in | |||||||
| <38 | 27,354 (20.9) | 27.3 | 16.7 | 10.6 | 21.5 | 20.3 | 1.2 |
| ≥38 to <39 | 14,419 (11.0) | 11.6 | 10.6 | 1.0 | 11.0 | 11.1 | −0.1 |
| ≥39 | 89,119 (68.1) | 61.2 | 72.7 | −11.5 | 67.5 | 68.7 | −1.2 |
| Hospital days during run-in | |||||||
| 0 | 88,885 (67.9) | 72.0 | 65.2 | 6.8 | 67.5 | 68.3 | −0.8 |
| >0 to <8 | 21,164 (16.2) | 14.9 | 17.0 | −2.1 | 16.3 | 16.1 | 0.2 |
| ≥8 | 20,843(16.0) | 13.1 | 17.8 | −4.7 | 16.2 | 15.6 | 0.6 |
| Estimated GFR (ml/min per 1.73 m2) | |||||||
| <10 | 69,641 (53.2) | 52.8 | 53.5 | −0.7 | 52.3 | 54.2 | −1.9 |
| 10 to <15 | 40,884 (31.2) | 31.4 | 31.1 | 0.3 | 31.6 | 30.8 | 0.8 |
| ≥15 | 18,787 (14.4) | 14.6 | 14.2 | 0.4 | 14.8 | 13.9 | 0.9 |
| Missing | 1580 (1.2) | 1.2 | 1.2 | 0.0 | 1.3 | 1.1 | 0.2 |
| Hemoglobin (g/dl) | |||||||
| <11 | 86,461 (66.1) | 66.0 | 66.1 | 0.1 | 66.3 | 65.9 | 0.4 |
| ≥11.0 | 35,354 (27.0) | 26.7 | 27.2 | −0.5 | 26.6 | 27.6 | −1.0 |
| Missing | 9077 (6.9) | 7.4 | 6.7 | 0.3 | 7.2 | 6.7 | 0.5 |
| Serum albumin (g/dl) | |||||||
| <3.4 | 59,174 (45.2) | 44.6 | 45.6 | −1.0 | 44.9 | 45.6 | −0.7 |
| ≥3.4 | 39,768 (30.4) | 30.0 | 30.6 | −0.6 | 29.5 | 31.3 | −1.8 |
| Missing | 31,950 (24.4) | 25.4 | 23.8 | 1.6 | 25.7 | 23.1 | 2.6 |
| BMI (kg/m2) | |||||||
| <18.5 | 4912 (3.8) | 3.8 | 3.7 | 0.1 | 3.8 | 3.7 | 0.1 |
| 18.5 to <25 | 42,962 (32.8) | 33.1 | 32.6 | 0.5 | 32.9 | 32.8 | 0.1 |
| ≥25 | 81,402 (62.2) | 61.9 | 62.4 | −0.5 | 62.1 | 62.3 | −0.2 |
| Missing | 1616 (1.2) | 1.2 | 1.3 | 0.1 | 1.3 | 1.2 | 0.1 |
Unless otherwise indicated, all data are expressed as percentages. ASHD, atherosclerotic heart disease; CHF, congestive heart failure; CVA/TIA, cerebrovascular accident/transient ischemic attack; PVD, peripheral vascular disease; COPD, chronic obstructive pulmonary disease; GI, gastrointestinal; SES, socioeconomic status; BMI, body mass index.
a
Medicare and Medicaid.
b
SES groups based on first principle component.