Table 2.
Distribution of selected characteristics of case patients with renal cell carcinoma and healthy control subjects*
| Variable | Case patients (n = 260) | Control subjects (n = 281) | P value† |
| Sex, No. (%) | |||
| Male | 172 (66) | 175 (62) | |
| Female | 88 (34) | 106 (38) | .348 |
| Smoking status, No. (%) | |||
| Never | 136 (52) | 126 (45) | |
| Former | 93 (36) | 107 (38) | |
| Current | 30 (12) | 48 (17) | .099 |
| Hypertension history, No. (%) | |||
| Yes | 144 (55) | 111 (40) | |
| No | 116 (45) | 170 (60) | <.001 |
| Body mass index, No. (%) | |||
| <25 kg/m2 | 52 (20) | 90 (32) | |
| ≥25 and <30 kg/m2 | 109 (42) | 104 (37) | |
| ≥30 kg/m2 | 99 (38) | 87 (31) | .006 |
| Age, mean (SD), y | 59.20 (10.57) | 59.52 (10.91) | .730 |
| Mean pack-years of smoking‡ (SD) | 28.95 (25.96) | 31.08 (31.93) | .547 |
| mtDNA content, copy number | |||
| Mean (SD) | 1.18 (0.43) | 1.29 (0.44) | .006 |
| Median (range) | 1.14 (0.44–4.67) | 1.22 (0.41–4.24) | .001 |
*
mtDNA = mitochondrial DNA.
†
Differences in the distribution of sex, smoking status, hypertension history, and body mass index were tested with the Pearson χ2 test. Student t test was used to test for differences in age, pack-years of smoking, and mtDNA content. All statistical tests were two-sided.
‡
Pack-years of smoking was assessed for ever smokers only.