Table 2.

Hazard ratios (95 % confidence interval) for the relation between CoW completeness and future ischemic stroke, after a mean follow-up of 9.2 ± 3.0 years (n = 976)

	Ischemic stroke (n = 30)	Anterior circulation stroke (n = 24)
Completeness of individual CoW collateral pathways
Anterior CoW completeness
Complete anterior CoW (n = 753)	1.0 (reference)	1.0 (reference)
Incomplete anterior CoW (n = 223)	1.9 (0.9–4.1)	2.8 (1.3–6.3)*
Posterior CoW completeness
Complete posterior CoW (n = 287)	1.0 (reference)	1.0 (reference)
One-sided incomplete posterior CoW (n = 291)	1.4 (0.5–3.6)	2.2 (0.7–7.1)
Two-sided incomplete posterior CoW (n = 398)	1.3 (0.5–3.2)	1.9 (0.6–5.9)
Completeness of combined anterior and posterior CoW collateral pathways
Complete anterior and posterior CoW (n = 233)	1.0 (reference)	1.0 (reference)
Complete anterior CoW, one-sided incomplete posterior CoW (n = 225)	1.2 (0.4–3.9)	2.5 (0.5–12.9)
Complete anterior CoW, two-sided incomplete posterior CoW (n = 295)	1.2 (0.4–3.6)	2.2 (0.4–10.9)
Incomplete anterior CoW, complete posterior CoW (n = 54)	1.6 (0.3–8.3)	4.0 (0.6–28.6)
Incomplete anterior CoW, one-sided incomplete posterior CoW (n = 66)	2.8 (0.7–10.3)	7.0 (1.3–38.2)*
Incomplete anterior CoW, two-sided incomplete posterior CoW (n = 103)	2.1 (0.6–7.4)	5.4 (1.0–27.8)*

CoW circle of Willis

*p < 0.05