Table 2.

Distributions of mtDNA copy number among cancer‐free controls

Selected variables	N	mtDNA copy number median (quartile)	P a
Overall	597	3.50 (1.93–11.22)
Age
<60	285	3.33 (1.94–9.23)	0.273
≥60	312	3.90 (1.89–12.84)
Gender
Male	374	3.46 (1.83–11.21)	0.48
Female	223	3.59 (2.06–11.85)
Smoking status
Never	344	3.51 (2.00–11.83)	0.627
Ever	253	3.47 (1.76–10.88)
Drinking status
Never	405	3.59 (1.90–12.09)	0.684
Ever	192	3.43 (2.00–9.44)

^aDerived from rank‐sum test for mtDNA copy number between subgroups divided by characteristics.