Table 2. Overall and subgroup analyses of mtDNA copy number with cancer risk by dichotomizing mtDNA copy number into high and low groups.
| Subgroups | Research counts (n) | Test of association |
95% CI | P | Heterogeneity |
I2 | Tau-squared | ||
|---|---|---|---|---|---|---|---|---|---|
| Model | OR | χ | p | ||||||
| Overall | 39 | Random | 1.044 | 0.866-1.260 | 0.651 | 499.08 | 0.000 | 92.4% | 0.3139 |
| Cancer types | |||||||||
| Lymphoma | 4 | Random | 1.645 | 1.117-2.421 | 0.012a | 6.20 | 0.102 | 51.6% | 0.0769 |
| Breast cancer | 5 | Random | 1.721 | 1.130-2.622 | 0.011a | 54.16 | 0.000 | 92.6% | 0.2015 |
| Lung cancer | 5 | Random | 0.982 | 0.788-1.223 | 0.871 | 7.84 | 0.097 | 49.0% | 0.2015 |
| Colorectal cancer | 3 | Random | 1.168 | 0.638-2.139 | 0.641 | 34.38 | 0.000 | 94.2% | 0.2681 |
| Renal carcinoma | 4 | Random | 0.856 | 0.598-1.226 | 0.397 | 19.71 | 0.000 | 84.8% | 0.1126 |
| Melanoma | 2 | Random | 1.555 | 0.598-4.045 | 0.365 | 15.73 | 0.000 | 93.6% | 0.4456 |
| Glioma | 2 | Random | 2.510 | 0.709-8.887 | 0.154 | 35.96 | 0.000 | 97.2% | 0.8091 |
| Gastric | 2 | Random | 0.412 | 0.054-3.134 | 0.392 | 25.76 | 0.000 | 96.1% | 2.0587 |
| Hepatic | 3 | Fixed | 0.622 | 0.486-0.798 | 0.000a | 0.53 | 0.767 | 0.0% | |
| Oral | 2 | Random | 0.946 | 0.295-3.029 | 0.925 | 12.43 | 0.000 | 92.0% | 0.6489 |
| Organ systems | |||||||||
| Digestive system | 12 | Random | 0.861 | 0.632-1.173 | 0.344 | 95.74 | 0.000 | 88.5% | 0.2521 |
| Urogenital system | 6 | Random | 0.876 | 0.635-1.209 | 0.420 | 43.03 | 0.000 | 88.4% | 0.1398 |
| Respiratory system | 6 | Random | 0.928 | 0.730-1.179 | 0.539 | 11.74 | 0.039 | 57.4% | 0.0488 |
| Gynecologica system | 6 | Random | 1.253 | 0.744-2.109 | 0.396 | 106.55 | 0.000 | 95.3% | 0.3847 |
| Population | |||||||||
| Western | 25 | Random | 0.951 | 0.719-1.259 | 0.728 | 456.55 | 0.000 | 94.7% | 0.4628 |
| East Asian | 11 | Random | 1.296 | 0.901-1.866 | 0.162 | 147.15 | 0.000 | 93.2% | 0.3481 |
| India | 2 | Fixed | 0.508 | 0.335-0.771 | 0.001 | 0.01 | 0.938 | 0.0% | |
| Africa | 1 | 0.799 | |||||||
| Ageb | |||||||||
| Elder | 10 | Random | 1.104 | 0.655-1.860 | 0.710 | 111.22 | 0.000 | 91.9% | 0.6352 |
| Younger | 10 | Random | 1.079 | 0.670-1.738 | 0.754 | 95.11 | 0.000 | 90.5% | 0.5213 |
| Gender | |||||||||
| Male | 16 | Random | 1.036 | 0.755-1.420 | 0.828 | 155.98 | 0.000 | 90.4% | 0.3578 |
| Female | 22 | Random | 1.109 | 0.866-1.420 | 0.414 | 191.26 | 0.000 | 89.0% | 0.2788 |
| Life styles | |||||||||
| Smoking status | |||||||||
| Ever/Frequent | 21 | Random | 0.984 | 0.765-1.267 | 0.902 | 106.17 | 0.000 | 81.2% | 0.2465 |
| Never/Occasionally | 18 | Random | 1.047 | 0.736-1.491 | 0.798 | 165.82 | 0.000 | 89.7% | 0.4972 |
| Drinking Status | |||||||||
| Ever/Frequent | 5 | Fixed | 1.261 | 1.076-1.479 | 0.004a | 4.53 | 0.340 | 11.6% | |
| Never/Occasionally | 5 | Random | 1.179 | 0.971-1.432 | 0.096 | 42.69 | 0.000 | 90.6% | 0.5403 |
| BMI | |||||||||
| Highc | 4 | Random | 1.103 | 0.413-2.942 | 0.845 | 36.84 | 0.000 | 91.9% | 0.9038 |
| Lowc | 4 | Random | 1.077 | 0.550-2.109 | 0.828 | 15.12 | 0.002 | 80.2% | 0.3609 |
ap < 0.05;
bAge was classified as elder and younger according to publication records; cRelative value which means relatively high and relatively low BMI.