Table 3.

Patient characteristics, overall and by paired quartiles.

		Paired quartiles
	Study sample	Q12	Q23	Q34	Q13	Q24	Q14
Number of patients	37,508	5649	3472	8049	5781	6035	9355
Race, n (%)
White	30,897 (82.4)	4874 (86.3)	2867 (82.6)	6302 (78.3)	4878 (84.4)	4916 (81.5)	7668 (82.0)
Non-white	6611 (17.6)	775 (13.7)	605 (17.4)	1747 (21.7)	903 (15.6)	1119 (18.5)	1687 (18.0)
Gender, n (%)
Female	20,884 (55.7)	3187 (56.4)	1880 (54.1)	4574 (56.8)	3208 (55.5)	3388 (56.1)	5127 (54.8)
Male	16,624 (44.3)	2462 (43.6)	1592 (45.9)	3475 (43.2)	2573 (44.5)	2647 (43.9)	4228 (45.2)
Low socioeconomic status, n (%)
No	28,191 (75.5)	4445 (79.0)	2563 (74.1)	5791 (72.3)	4379 (76.2)	4411 (73.6)	7145 (76.7)
Yes	9126 (24.5)	1179 (21.0)	894 (25.9)	2219 (27.7)	1370 (23.8)	1585 (26.4)	2167 (23.3)
Region, n (%)
Midwest	8604 (22.9)	1608 (28.5)	901 (26.0)	1641 (20.4)	1277 (22.1)	1484 (24.6)	1871 (20.0)
Northeast	6083 (16.2)	357 (6.3)	315 (9.1)	1852 (23.0)	699 (12.1)	941 (15.6)	2020 (21.6)
South	16,763 (44.7)	2399 (42.5)	1734 (49.9)	3610 (44.9)	2629 (45.5)	2572 (42.6)	4194 (44.8)
West	5849 (15.6)	1284 (22.7)	516 (14.9)	827 (10.3)	1156 (20.0)	1014 (16.8)	1223 (13.1)
Other	209 (0.6)	1 (0.0)	6 (0.2)	119 (1.5)	20 (0.3)	24 (0.4)	47 (0.5)
Time between paired admissions (days)
Median	NA	118.0	113.0	111.0	114.0	112.0	113.0
IQR	NA	70.0–184.0	68.0–177.0	67.0–175.0	68.0–182.0	69.0–177.0	69.0–178.0

Number of patients may not sum to total due to missing values (191 patients in the study sample had missing values in the low socioeconomic status variable); NA: In the study sample, patients might have had >2 admissions; the time between paired admissions is not available; IQR, interquartile range; Q, quartile-pair (e.g., Q12, quartile-pair comparison Q1 vs. Q2); Beneficiaries with low socioeconomic status were defined as those in the lowest quartile group of the Agency for Healthcare Research and Quality socioeconomic status index score, a composite measure of socioeconomic status that was calculated based on 7 measures from the census data.²⁰