Risk factors | Category | Relative risk (95Â % CI) | Study design | Source | Prevalence (%)a | Source |
---|---|---|---|---|---|---|
Breast cancer | Â | Â | Â | Â | Â | Â |
 Pregnancy/age at first birth | Nulliparous | 1.06 (0.82-1.36) | Case–control study | SeBCS | 3 | KNHANES, 2005 |
 | ≤23 years | 1.00 |  |  | 36 |  |
 | 24 – 30 year | 1.13 (0.98-1.32) |  |  | 57 |  |
 | ≥31 year | 1.27 (0.98-1.66) |  |  | 4 |  |
 Total period of breast feeding | Never | 1.03 (0.87-1.21) | Case–control study | SeBCS | 17 (18b) | KNHANES, 2005 |
 | ≤6 months | 1.28 (1.07-1.53) |  |  | 9 (10b) |  |
 | ≥7 months | 1.00 |  |  | 70 (72b) |  |
 Oral contraceptive use | Never | 1.00 | Meta-anlaysis | SeBCS and [31] | 82 | KNHANES, 2005 |
 | Ever | 1.31 (1.04-1.64) |  |  | 18 |  |
 Hormone replacement therapy use | Never | 1.00 |  |  | 30 (95c) | KNHANES, 2005 |
 | Ever | 1.16 (0.36-3.78) | Meta-anlaysis | SeBCS and [31] | 2 (5c) |  |
Ovarian cancer | Â | Â | Â | Â | Â | Â |
 Pregnancy | Nulliparous | 1.42 (1.31-1.54) | Meta-anlaysis | 3 | KNHANES, 2005 | |
 | Parous | 1.00 |  |  | 97 |  |
 Breast feeding experience | Never | 1.17 (1.02-1.33) | Meta-anlaysis | 17 (18b) | KNHANES, 2005 | |
 | Ever | 1.00 |  |  | 79(82b) |  |
 Tubal ligation | No | 1.44 (1.33-1.56) | Meta-anlaysis | Ko-EVE and [44] | 75 (77b) | Ko-EVEd, 2009-2011 |
 | Yes | 1.00 |  |  | 22 (23b) |  |
 Oral contraceptive use | Never | 1.87 (0.89-3.94) | Meta-anlaysis | Ko-EVE and [45] | 82 | KNHANES, 2005 |
 | Ever | 1.00 |  |  | 18 |  |