TABLE 1.

General Characteristics of Case and Control Groups

Groups	Cases	Onset or Inclusion Age (yr.)		Course of Disease (day)
		Range	$\overline{x}\pm SD$	Range	$\overline{x}\pm SD$
sMTS	22	31.0–54.0	42.3 ± 6.5	1.0–40.0	12.1 ± 9.2
dMTS	33	43.0–81.0	61.5 ± 10.6	2.0–120.0	22.5 ± 7.6
oIVCS	14	24.0–76.0	53.1 ± 16.8	3.0–30.0	6.8 ± 6.7
Control	380	15.0–92.0	47.4 ± 23.0	–	---
Statistical analysist*,†	449	F = 5.135,P = 0.002; (Ps-d = 0.008, Pd-c = 0.002; Ps-o, Ps-c, Pd-o and Po-c all p > 0.05)		F = 7.806,P = 0.002 ( Ps-d = 0.010, Pd-o = 0.010, Ps-o = 0.690)

^*c indicates control group; d/dMTS, low lumbar degeneration-related May-Thurner syndrome; o/oIVCS, other cause iliac vein compression; s/sMTS simple May-Thurner syndrome.

Ps-c means comparison among sMTS and its control group, and so on.

^†Bofferroni test was used in the statistical correction of multiple comparisons of means.