Table 2.

Descriptive statistics of qualified MarketScan^® procedures records (n = 7,702,846). SSI: Surgical site infection.

Variable	All		No SSI		SSI during admission		SSI after discharge
	Mean (SD)	Range	Mean (SD)	Range	Mean (SD)	Range	Mean (SD)	Range
Age (years)	50.2 (16.8)	18–108	50.2 (16.8)	18–108	55.3 (14.9)	18–98	50.1 (16.3)	18–105
Charlson comorbidity Index	2.4 (2.9)	0–26	2.4 (2.9)	0–26	3.9 (3.4)	0–22	2.8 (3.1)	0–23
Length of stay (days)	3.5 (5.3)	1–541	3.5 (5.2)	1–541	10.2 (11.9)	1–307	4.5 (6.8)	1–342
Maximum daily precipitation (mm/day)	33.6 (21.2)	0–231	33.6 (21.2)	0–231	32.1 (20.8)	0–221	33.9 (21.4)	0–221
Mean daily precipitation (mm/day)	2.9 (1.8)	0–21	2.9 (1.8)	0–21	2.9 (1.9)	0–16.6	2.9 (1.8)	0–18.5
Maximum daily specific humidity (kg/kg)	0.012 (0.004)	0.001–0.02	0.012 (0.004)	0.001–0.02	0.011 (0.004)	0.001–0.02	0.011 (0.004)	0.002–0.02
Mean daily specific humidity (kg/kg)	0.007 (0.004)	0.001–0.02	0.007 (0.004)	0.001–0.02	0.007 (0.004)	0.001–0.02	0.007 (0.004)	0.001–0.02
Maximum daily maximum temperature (°C)	28.7 (7.6)	− 4.3–47.7	28.7 (7.9)	− 4.3–47.7	28.1 (8.1)	0.2–46.3	28.9 (7.8)	− 2.2–47.7
Mean daily maximum temperature (°C)	19.7 (9.8)	− 12.9–43.2	19.7 (9.8)	− 12.9–43.2	19.5 (9.9)	− 10.6–42.3	20 (9.7)	− 11.8–43.2
Minimum daily maximum temperature (°C)	9.4 (11.7)	− 27.1–39.9	9.4 (11.7)	− 27.1–39.9	9.8 (11.7)	− 25–38.5	9.6 (11.6)	− 26.5–39.9
Maximum daily minimum temperature (°C)	16 (7.1)	− 16.7–31.7	16 (7.1)	− 16.7–31.7	15.6 (7.3)	− 11.2–31.6	16.2 (7.1)	− 13.7–31.4
Mean daily minimum temperature (°C)	7.7 (8.8)	− 27.2–28.6	7.7 (8.8)	− 27.2–28.6	7.6 (8.9)	− 21.9–27.3	8 (8.8)	− 24.1–27.9
Minimum daily minimum temperature (°C)	− 1.3 (10.6)	− 38.2–25.5	− 1.3 (10.6)	− 38.2–25.5	− .94 (10.7)	− 37.6–24.1	− 1 (10.6)	-38.2–25.1