Table 3. Associations between dichotomous pigmentation traits for stage 1.

Pigmentation trait	p (padj)	p (padj)a	OR (95% CI)	OR (95% CI)a
Eye colour (blue)
Hair colour (blond)	<1.0 × 10−5 (3.0 × 10−5)	0.0047 (0.014)	3.6 (2.1–6.2)	2.7 (1.3–5.5)
Hair colour (red tint)
Skin type (fair, I–II)	<1.0 × 10−5 (3.0 × 10−5)	3.0 × 10−4 (9.0 × 10−4)	4.1 (2.4–7.2)	3.1 (1.7–5.6)
Hair colour (blond)b
Eye colour (blue)	1.0 × 10−5 (3.0 × 10−5)	<1.0 × 10−5 (3.0 × 10−5)c	3.6 (2.1–6.3)	4.4 (2.5–7.8)c
Skin type (fair, I–II)
Hair colour (red)	<1.0 × 10−5 (3.0 × 10−5)	<1.0 × 10−5 (3.0 × 10−5)d	5.7 (3.1–10.2)	5.7 (3.1–10.2)d
Hair colour (blond)	2.7 × 10−4 (8.1 × 10−4)	2.7 × 10−4 (8.1 × 10−4)d	2.9 (1.6–5.2)	2.9 (1.6–5.2)d

Abbreviations: CI, confidence interval; OR, odds ratio; SNP, single-nucleotide polymorphism.

p_adj: Bonferroni-adjusted P-value (three tests). All associations were evaluated in a multiple logistic regression analysis treating the remaining three traits as influential variables, and by backward selection.

^aP-values and ORs are from a multiple logistic regression analysis including the predictive SNPs from Table 2 as influential variables.

^bIn the analysis of the light-dark component of hair colour, two individuals with pure red hair colour were removed.

^cMultiple logistic regression analysis including the predictive SNPs of Table 2 eventually disregarded rs12913832 (HERC2) after backward selection.

^dMultiple logistic regression analysis eventually disregarded all predictive SNPs from Table 2 after backward selection.