Table 2.

Association between disc degeneration at the L3/L4 and L4/L5 disc levels and the carriage of Trp3, COL2A1 (A) and the IL-1βT³⁹⁵⁴ alleles

	Dark nucleus pulposus		Disc bulges		Decreased disc height		Summary score
	OR	95% CI	OR	95% CI	OR	95% CI	OR	95% CI
Absence of the Trp3 allele	1.0		1.0		1.0		1.0
Carriage of the Trp3 allele in the absence of the IL-1βT3954	7.0	1.3–38.8	1.4	0.3–6.9	4.3	0.8–21.6	8.0	1.4–44.7
Carriage of both alleles	0.8	0.3–2.2	1.1	0.4–2.9	0.5	0.2–1.5	0.9	0.3–2.4
Absence of the Trp3 and COL2A1 minor allele	1.0		1.0		1.0		1.0
Carriage of either the Trp3 or COL2A1 minor allele in the absence of the IL-1βT3954	3.5	1.0–11.5	0.7	0.2–2.5	1.9	0.6–6.1	3.9	1.2–13.0
Carriage of either the Trp3 or COL2A1 minor allele and the IL-1βT3954 allele	0.9	0.4–2.1	1.3	0.5–3.1	0.5	0.2–1.2	0.9	0.4–2.2

Disc degeneration is assessed as the number of discs with degenerative signs. Proportional odds model. Odds ratios (OR) and their 95% confidence intervals (CI) are adjusted for occupation and BMI at the age of 40–45 years