Table 3. ORs and 95% CI for mtDNA copy number and risk of oral cancer.

mtDNA copy number quartile	Cases (n = 124)	Controls (n = 140)	OR (95%CI)
Quartile 1 (≤0.1)	58	43	2.92[1.32–6.43]
Quartile 2 (>0.1–1)	35	42	1.80[0.79–4.09]
Quartile 3 (>1–10)	19	29	1.41[0.57–3.47]
Quartile 4 (>10)	12	26	1 (ref)
P trend 0.003