Table 1.
Distribution of breast cancer risk factors in cases and controls in the Nigerian Breast Cancer Study (1998–2015)
| Characteristics | Case | Control | Age-adjusted odds ratio | P | Ptrend |
|---|---|---|---|---|---|
| N | 1811 | 2225 | |||
| Age group | <0.001 | <0.001 | |||
| <25 | 9 (0.5) | 153 (6.9) | 0.06 (0.03–0.13) | ||
| 25~29.9 | 59 (3.3) | 212 (9.5) | 0.30 (0.21–0.41) | ||
| 30~34.9 | 151 (8.3) | 314 (14.1) | 0.51 (0.40–0.66) | ||
| 35~39.9 | 273 (15.1) | 327 (14.7) | 0.89 (0.71–1.12) | ||
| 40~44.9 | 297 (16.4) | 317 (14.3) | 1.00 | ||
| 45~49.9 | 306 (16.9) | 263 (11.8) | 1.24 (0.99–1.56) | ||
| 50~54.9 | 254 (14.0) | 222 (10.0) | 1.22 (0.96–1.55) | ||
| 55~59.9 | 176 (9.7) | 145 (6.5) | 1.30 (0.99–1.70) | ||
| 60~64.9 | 132 (7.3) | 139 (6.3) | 1.01 (0.76–1.35) | ||
| 65~69.9 | 75 (4.1) | 67 (3.0) | 1.19 (0.83–1.72) | ||
| 70~74.9 | 50 (2.8) | 43 (1.9) | 1.24 (0.80–1.92) | ||
| ≥75 | 29 (1.6) | 23 (1.0) | 1.35 (0.76–2.38) | ||
| Age at menarche | 0.017 | 0.013 | |||
| ≥17 | 421 (23.3) | 564 (25.4) | 1.00 | ||
| 16~16.9 | 255 (14.1) | 343 (15.4) | 1.02 (0.83–1.26) | ||
| 15~15.9 | 515 (28.4) | 538 (24.2) | 1.33 (1.11–1.59) | ||
| 14~14.9 | 255 (14.1) | 341 (15.3) | 1.09 (0.88–1.35) | ||
| 13~13.9 | 186 (10.3) | 219 (9.8) | 1.27 (1.00–1.62) | ||
| 12~12.9 | 151 (8.3) | 171 (7.7) | 1.30 (1.00–1.69) | ||
| 8~11.9 | 28 (1.6) | 49 (2.2) | 0.86 (0.52–1.42) | ||
| Benign breast diseases | 207 (11.4) | 144 (6.5) | 1.80 (1.43–2.26) | <0.001 | <0.001 |
| Family history of breast cancer | 95(5.3) | 68 (3.1) | 1.96 (1.40–2.74) | <0.001 | <0.001 |
| Parity | <0.001 | 0.001 | |||
| 0 | 155 (8.6) | 246 (11.1) | 1.00 | ||
| 1 | 126 (7.0) | 209 (9.4) | 0.57 (0.40–0.80) | ||
| 2 | 198 (10.9) | 268 (12.0) | 0.48 (0.35–0.66) | ||
| 3 | 287 (15.8) | 326 (14.7) | 0.49 (0.36–0.67) | ||
| 4 | 297 (16.4) | 393 (17.7) | 0.36 (0.26–0.49) | ||
| 5 | 306 (16.9) | 325 (14.6) | 0.41 (0.30–0.56) | ||
| 6 | 213 (11.8) | 206 (9.3) | 0.41 (0.29–0.58) | ||
| 7 | 119 (6.6) | 124 (5.6) | 0.37 (0.25–0.54) | ||
| ≥8 | 110 (6.1) | 128 (5.8) | 0.32 (0.22–0.47) | ||
| Age of first live birth | <0.001 | <0.001 | |||
| <20 | 352 (19.6) | 428 (19.3) | 1.00 | ||
| 20~24.9 | 679 (37.7) | 827 (37.2) | 1.00 (0.83–1.19) | ||
| 25~29.9 | 419 (23.3) | 542 (24.4) | 0.98 (0.80–1.19) | ||
| ≥30 | 195 (10.8) | 178 (8.0) | 1.25 (0.97–1.60) | ||
| No birth | 155 (8.6) | 246 (11.1) | 2.25 (1.67–3.04) | ||
| Age at menopause | 0.536 | 0.384 | |||
| <35 | 26 (3.23) | 12 (1.90) | 0.57 (0.201.63) | ||
| 35~44.9 | 162 (20.15) | 96 (15.19) | 1.04 (0.75–1.45) | ||
| 45~54.9 | 521 (64.80) | 444 (70.25) | 1.00 | ||
| ≥55 | 95 (11.82) | 80 (12.66) | 1.19 (0.84–1.69) | ||
| Total month of breastfeeding | <0.001 | <0.001 | |||
| <12 | 225 (12.4) | 342 (15.4) | 1.00 | ||
| 12~23.9 | 155 (8.6) | 193 (8.7) | 0.71 (0.53–0.96) | ||
| 24~35.9 | 224 (12.4) | 263 (11.8) | 0.56 (0.42–0.71) | ||
| 36~47.9 | 207 (11.5) | 224 (10.1) | 0.57 (0.43–0.77) | ||
| 48~59.9 | 215 (11.9) | 263 (11.8) | 0.47 (0.35–0.63) | ||
| 60~71.9 | 163 (9.0) | 225 (10.1) | 0.37 (0.40–0.72) | ||
| 72~83.9 | 215 (11.9) | 203 (9.1) | 0.53 (0.40–0.72) | ||
| 84~95.9 | 82 (4.5) | 103 (4.6) | 0.38 (0.26–0.55) | ||
| ≥96 | 325 (18.0) | 409 (18.4) | 0.35 (0.26–0.46) | ||
| Height in cm | <0.001 | <0.001 | |||
| <150 | 85 (4.7) | 136 (6.1) | 0.91 (0.68–1.23) | ||
| 150~159 | 654 (36.1) | 1067 (48.0) | 1.00 | ||
| 160~169 | 819 (45.2) | 885 (39.8) | 1.58 (1.37–1.82) | ||
| ≥170 | 253 (14.0) | 137 (6.2) | 3.26 (2.57–4.15) | ||
| Body mass index in kg/m2 | |||||
| Before menopause | 0.001 | 0.004 | |||
| 18.5~24.9 | 425 (44.1) | 700 (44.8) | 1.00 | ||
| <18.5 | 67 (7.0) | 95 (6.1) | 1.43 (1.00–2.05) | ||
| 25~29.9 | 276 (28.6) | 432 (27.6) | 0.89 (0.73–1.09) | ||
| ≥30 | 196 (20.3) | 338 (21.6) | 0.71 (0.57–0.89) | ||
| After menopause | <0.001 | <0.001 | |||
| 18.5~24.9 | 327 (38.6) | 191 (28.9) | 1.00 | ||
| <18.5 | 55 (6.5) | 28 (4.2) | 1.12 (0.68–1.85) | ||
| 25~29.9 | 242 (28.6) | 248 (37.6) | 0.57 (0.44–0.74) | ||
| ≥30 | 223 (26.3) | 193 (29.2) | 0.68 (0.52–0.89) | ||
| Waist-hip ratio | 0.061 | 0.055 | |||
| <0.80 | 453 (25.4) | 599 (27.5) | 1.00 | ||
| 0.80~0.84 | 458 (25.7) | 528 (24.3) | 1.04 (0.87–1.25) | ||
| ≥0.85 | 871 (48.9) | 1050 (48.2) | 0.87 (0.74–1.02) | ||
| Oral contraceptive | 512 (28.3) | 741 (33.4) | 0.75 (0.65–0.86) | <0.001 | <0.001 |
| Alcohol consumption | 179 (9.9) | 109 (4.9) | 1.95 (1.52–2.52) | <0.001 | <0.001 |
| Study periods | 0.009 | 0.389 | |||
| 1998~2004 | 619 (34.2) | 732 (32.9) | 1.00 | ||
| 2005~2010 | 588 (32.5) | 770 (34.6) | 0.79 (0.67–0.92) | ||
| 2011~2015 | 604 (33.4) | 723 (32.5) | 0.93 (0.80–1.09) |
Note: There were 15, 71, 77 and 10 women with missing in age of first birth, age at menopause, waist-hip ratio and oral contraceptive, respectively.
P value and Ptrend value were all adjusted by age.