1Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea
2Cancer Research Institute, Seoul National University, Seoul, Korea
3Department of Biomedical Science, Seoul National University Graduate School, Seoul, Korea
4National Cancer Center Graduate School of Cancer Science and Policy, Goyang, Korea
5National Cancer Control Institute, National Cancer Center, Goyang, Korea
6Department of Surgery, Soonchunhyang University College of Medicine, Seoul, Korea
7Department of Surgery, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea
8Armed Forces Capital Hospital, Seongnam, Korea
Copyright © 2017 The Korean Society for Preventive Medicine
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
CONFLICT OF INTEREST
The authors have no conflicts of interest associated with the material in this paper.
Total women |
Premenopausal women |
Postmenopausal women |
|||||||
---|---|---|---|---|---|---|---|---|---|
BC cases n (%) | Controls n (%) | OR (95% CI) | BC cases n (%) | Controls n (%) | OR (95% CI) | BC cases n (%) | Controls n (%) | OR (95% CI) | |
Parity | |||||||||
Nullipara | 291 (2.3) | 144 (1.1) | 1.35 (1.06, 1.69) | 152 (2.4) | 94 (1.5) | 1.16 (0.86-1.59) | 139 (2.12) | 50 (0.8) | 1.72 (1.18, 2.50) |
Para | 12 598 (97.7) | 12 745 (98.9) | 1.00 (reference) | 6170 (97.6) | 6228 (98.5) | 1.00 (reference) | 6428 (97.9) | 6517 (99.2) | 1.00 (reference) |
No. of childbirths | |||||||||
0 | 291 (2.3) | 144 (1.1) | 1.00 (reference) | 152 (2.4) | 94 (1.5) | 1.00 (reference) | 139 (2.1) | 50 (0.8) | 1.00 (reference) |
1 | 2046 (15.9) | 1370 (10.6) | 0.88 (0.69, 1.14) | 1200 (19.0) | 853 (13.5) | 1.01 (0.74, 1.39) | 846 (12.9) | 517 (7.9) | 0.72 (0.48, 1.06) |
2 | 7461 (57. 9) | 7552 (58.6) | 0.71 (0.61, 0.83) | 4248 (67.2) | 4526 (71.6) | 0.80 (0.65, 0.97) | 3213 (48.9) | 3026 (46.1) | 0.58 (0.45, 0.74) |
3+ | 3091 (24.0) | 3823 (29.7) | 0.62 (0.54, 0.80) | 722 (11.4) | 849 (13.4) | 0.81 (0.70, 0.94)1 | 2369 (36.1) | 2974 (45.3) | 0.40 (0.35, 0.43)1 |
Breastfeeding | |||||||||
No children | 291 (2.3) | 144 (1.1) | 1.38 (1.10, 1.75) | 152 (2.4) | 94 (1.5) | 1.17 (0.86, 1.58) | 139 (2.1) | 50 (0.8) | 1.80 (1.24, 2.62) |
Never | 2966 (23.0) | 1975 (15.3) | 1.00 (reference) | 1945 (30.8) | 1340 (21.2) | 1.00 (reference) | 1021 (15.6) | 635 (9. 7) | 1.00 (reference) |
Ever | 9632 (74.7) | 10 770 (83.6) | 0.60 (0.55, 0.64) | 4225 (66.8) | 4888 (77.3) | 0.59 (0.54, 0.65) | 5407 (82.3) | 5882 (89.6) | 0.60 (0.53, 0.68) |
Breastfeeding duration (mo) | |||||||||
0 | 3257 (25.3) | 2119 (16.4) | 1.00 (reference) | 2097 (33.2) | 1434 (22.7) | 1.00 (reference) | 1160 (17.7) | 685 (10.4) | 1.00 (reference) |
1-12 | 4116 (31.9) | 3624 (28.1) | 0.77 (0.71, 0.84) | 2372 (37.5) | 2470 (39.1) | 0.67 (0.60, 0.74)1 | 1744 (26.6) | 1154 (17.6) | 0.99 (0.86, 1.14)1 |
13-24 | 2901 (22.5) | 3576 (27.7) | 0.57 (0.52, 0.62) | 1293 (20.5) | 1711 (27.1) | 0.55 (0.48, 0.62) | 1608 (24.5) | 1865 (28.4) | 0.60 (0.52, 0.70) |
25+ | 1973 (15.3) | 3002 (23.3) | 0.41 (0.37, 0.46) | 398 (6.3) | 599 (9.5) | 0.44 (0.37, 0.53) | 1575 (24.0) | 2403 (36.6) | 0.44 (0.38, 0.52) |
The OR (95% CI) in all women was estimated in conditional logistic regression stratified by age and enrollment year and adjusted for family history of BC, age at menarche, age at first full-term pregnancy, duration of oral contraceptive use, BMI, and breastfeeding duration in the analyses of parity and number of childbirths; or adjusted for family history of BC, age at menarche, age at first full-term pregnancy, duration of oral contraceptive use, BMI, and number of childbirths in the analyses of breastfeeding and its duration. The OR (95% CI) in premenopausal and postmenopausal women was estimated in an unconditional logistic regression model stratified by age and year and adjusted for same covariates.
BC, breast cancer; OR, odds ratio; CI, confidence interval; BMI, body mass index.
1 p-value for the heterogeneity of two ORs (95% CIs) from 2 subgroups classified by menopausal status: p<0.001 for [childbirths=3+]; p<0.001 for [breastfeeding=1-12 months].
Total women |
Premenopausal women |
Postmenopausal women |
||||
---|---|---|---|---|---|---|
HR+ | HR- | HR+ | HR- | HR+ | HR- | |
No. of childbirths | ||||||
0 | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) |
1 | 0.78 (0.61, 0.99) | 1.25 (0.87, 1.79) | 0.94 (0.69, 1.30)2 | 1.64 (0.96, 2.78)2 | 0.57 (0.39, 0.85)2 | 0.88 (0.53, 1.47)2 |
2 | 0.52 (0.44, 0.60)1 | 1.04 (0.83, 1.30)1 | 0.62 (0.50, 0.78)2,3 | 1.31 (0.92, 1.86)2 | 0.48 (0.37, 0.61)2,3 | 0.78 (0.57, 1.07)2 |
3+ | 0.39 (0.34, 0.46)1 | 1.05 (0.86, 1.18)1 | 0.55 (0.48, 0.61)2 | 1.39 (0.99, 1.83)2 | 0.22 (0.18, 0.25)2 | 0.73 (0.57, 0.99)2 |
Breastfeeding duration (mo) | ||||||
0 | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) |
1-12 | 0.74 (0.69, 0.80) | 0.77 (0.68, 0.87) | 0.67 (0.61, 0.73)2,3 | 0.65 (0.55, 0.77)2 | 1.03 (0.89, 1.20)2,3 | 0.94 (0.78, 1.13)2 |
13-24 | 0.52 (0.48, 0.57) | 0.52 (0.46, 0.60) | 0.53 (0.48, 0.59) | 0.48 (0.39, 0.58) | 0.64 (0.55, 0.74) | 0.55 (0.46, 0.67) |
25+ | 0.40 (0.37, 0.44) | 0.40 (0.34, 0.47) | 0.45 (0.38, 0.52) | 0.49 (0.37, 0.66) | 0.48 (0.41, 0.57) | 0.40 (0.32, 0.49) |
Values are presented as OR (95% CI).
The OR (95% CI) in all women was estimated in conditional logistic regression stratified by age and enrollment year and adjusted for family history of BC, age at menarche, age at first full-term pregnancy, duration of oral contraceptive use, BMI, and breastfeeding duration in the analyses of parity and number of childbirths; or adjusted for family history of BC, age at menarche, age at first full-term pregnancy, duration of oral contraceptive use, BMI, and number of childbirths in the analyses of breastfeeding and its duration.
HR, hormone receptor; BC, breast cancer; OR, odds ratio; CI, confidence interval; BMI, body mass index.
1 p-value for the heterogeneity of two ORs (95% CIs) from HR+ subgroup and HR- subgroup in total women: <0.001 for [childbirths=2]; <0.001 for [childbirths=3+].
2 p-value for the heterogeneity of four ORs (95% CIs) from 4 subgroups classified by HR and menopausal status: 0.017 for [childbirths=1]; <0.001 for [childbirths=2]; <0.001 for [childbirths=3+]; <0.001 for [breastfeeding=1-12 months].
3 p-value for the heterogeneity of two ORs (95% CIs) from 2 subgroups classified by menopausal status in HR+ groups = 0.134 for [childbirths=2]; <0.001 for [breastfeeding=1-12 months].
Total women |
Premenopausal women |
Postmenopausal women |
||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Luminal A | Luminal B | HER2-enriched | Triple-negative | Luminal A | Luminal B | HER2-enriched | Triple-negative | Luminal A | Luminal B | HER2-enriched | Triple-negative | |
No. of childbirths | ||||||||||||
0 | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) |
1 | 0.72 (0.58, 0.88)1 | 0.87 (0.55, 1.25)1 | 1.43 (0.83, 2.38)1 | 1.19 (0.78, 1.82)1 | 1.01 (0.72, 1.39)2 | 0.83 (0.49, 1.39)2 | 1.77 (0.81, 4.00)2 | 1.69 (0.90, 3.13)2 | 0.56 (0.37,0.83)3 | 0.85 (0.42, 1.72)3 | 1.06 (0.52, 2.17)3 | 0.80 (0.44, 1.45)3 |
2 | 0.45 (0.40, 0.51)1 | 0.80 (0.63, 1.03)1 | 1.23 (0.88, 1.74)1 | 0.96 (0.75, 1.25)1 | 0.63 (0.50, 0.79)2 | 0.88 (0.65, 1.17)2 | 1.38 (0.84, 2.36)2 | 1.41 (0.94, 2.09)2 | 0.36 (0.27, 0.47)3 | 0.74 (0.48, 1.16)3 | 1.04 (0.66, 1.65)3 | 0.64 (0.44, 0.91)3 |
3+ | 0.34 (0.30, 0.38)1 | 0.74 (0.61, 0.91)1 | 1.10 (0.83, 1.48)1 | 0.92 (0.73, 1.15)1 | 0.55 (0.46, 0.66)2 | 0.89 (0.72, 1.08)2 | 1.13 (1.08, 1.68)2 | 1.68 (1.21, 2.28)2 | 0.26 (0.20, 0.33)3 | 0.65 (0.44, 0.99)3 | 1.03 (0.68, 1.59)3 | 0.56 (0.40, 0.78)3 |
Breastfeeding duration (mo) | ||||||||||||
0 | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) |
1-12 | 0.73 (0.68, 0.79) | 0.80 (0.68, 0.92) | 0.84 (0.70, 0.99) | 0.71 (0.62, 0.83) | 0.67 (0.61, 0.74)4 | 0.69 (0.57, 0.83)4 | 0.68 (0.53, 0.87)2 | 0.61 (0.51, 0.75)4 | 0.87 (0.76, 0.99)4 | 1.00 (0.78, 1.28)4 | 1.00 (0.79, 1.27)4 | 0.88 (0.70, 1.11)4 |
13-24 | 0.51 (0.45, 0.55) | 0.63 (0.53, 0.74) | 0.50 (0.42, 0.61) | 0.52 (0.44, 0.61) | 0.51 (0.45, 0.57) | 0.65 (0.51, 0.87) | 0.50 (0.37, 0.67) | 0.45 (0.36, 0.57) | 0.50 (0.44, 0.57) | 0.60 (0.46, 0.77) | 0.48 (0.37, 0.63) | 0.59 (0.47, 0.75) |
25+ | 0.39 (0.36, 0.43) | 0.42 (0.34, 0.51) | 0.40 (0.32, 0.50) | 0.37 (0.31, 0.45) | 0.45 (0.38, 0.53) | 0.44 (0.31, 0.63) | 0.68 (0.44, 1.03) | 0.39 (0.27, 0.55) | 0.38 (0.33, 0.43) | 0.43 (0.33, 0.58) | 0.35 (0.27, 0.47) | 0.41 (0.32, 0.53) |
Values are presented as OR (95% CI).
The OR (95% CI) in all women was estimated in conditional logistic regression stratified by age and enrollment year and adjusted for family history of BC, age at menarche, age at first full-term pregnancy, duration of oral contraceptive use, BMI, and breastfeeding duration in the analyses of parity and number of childbirths; or adjusted for family history of BC, age at menarche, age at first full-term pregnancy, duration of oral contraceptive use, BMI, and number of childbirths in the analyses of breastfeeding and its duration.
HR, hormone receptor; BC, breast cancer; OR, odds ratio; CI, confidence interval; BMI, body mass index.
1 p-value for the heterogeneity of four ORs (95% CIs) from 4 pathological subtypes among total women =0.035 for [childbirths=1]; 0.001 for [childbirths=2]; <0.001 for [childbirths=3+].
2 p-value for the heterogeneity of four ORs (95% CIs) from 4 pathological subtypes among premenopausal women : 0.021 for [childbirths=1]; 0.001 for [childbirths=2]; <0.001 for [childbirths=3+].
3 p-value for the heterogeneity of four ORs (95% CIs) from 4 pathological subtypes among postmenopausal women: 0.401 for [childbirths=1]; <0.001 for [childbirths=2]; <0.001 for [childbirths=3+].
4 p-value for the heterogeneity of eight ORs (95% CIs) from 8 subgroups classified by pathological subtypes and menopausal status: <0.001 for [breastfeeding period =1-12 months].
No. of childbirths | Breastfeeding duration (mo) | Premenopausal women | Postmenopausal women |
---|---|---|---|
0 | 0 | 1.00 (reference) | 1.00 (reference) |
1 | 0 | 0.98 (0.70, 1.39) | 0.65 (0.43, 0.99) |
2 | 0 | 0.78 (0.69, 0.92) | 0.63 (0.54, 0.73) |
3+ | 0 | 0.89 (0.86, 0.94)1 | 0.47 (0.44, 0.50)1 |
1 | 1-12 | 0.65 (0.58, 0.74) | 0.64 (0.55, 0.74) |
1 | 13-24 | 0.69 (0.51, 0.60) | 0.49 (0.42, 0.58) |
2 | 1-12 | 0.52 (0.45, 0.61) | 0.52 (0.43, 0.62) |
3+ | 1-12 | 0.63 (0.59, 0.68) | 0.70 (0.61, 0.80) |
2 | 13-24 | 0.44 (0.39, 0.51) | 0.36 (0.30, 0.44) |
2 | 25+ | 0.36 (0.34, 0.39)1 | 0.27 (0.23, 0.32)1 |
3+ | 13-24 | 0.36 (0.35, 0.38)1 | 0.29 (0.25, 0.33)1 |
3+ | 25+ | 0.34 (0.32, 0.38)1 | 0.21 (0.18, 0.26)1 |
Values are presented as OR (95% CI).
The OR (95% CI) in all women was estimated in conditional logistic regression stratified by age and enrollment year and adjusted for family history of BC, age at menarche, age at first full-term pregnancy, duration of oral contraceptive use, BMI, and breastfeeding duration in the analyses of parity and number of childbirths; or adjusted for family history of BC, age at menarche, age at first full-term pregnancy, duration of oral contraceptive use, BMI, and number of childbirths in the analyses of breastfeeding and its duration. The calculated actual OR values in premenopausal and postmenopausal women was estimated using an unconditional logistic regression model stratified by age and year and adjusted for same covariates.
BC, breast cancer, OR, odds ratio; CI, confidence interval; BMI, body mass index.
1 p-value for the heterogeneity of two ORs (95% CIs) from 2 subgroups classified by menopausal status: <0.001 for [children=3+ and never breastfeeding] 0.005 for [children=3+ and breastfeeding=13-24 months]; 0.002 for [children=2 and breastfeeding=25+ months]; <0.001 for [children=3+ and breastfeeding=25+ months].
Total women |
Premenopausal women |
Postmenopausal women |
|||||||
---|---|---|---|---|---|---|---|---|---|
BC cases n (%) | Controls n (%) | OR (95% CI) | BC cases n (%) | Controls n (%) | OR (95% CI) | BC cases n (%) | Controls n (%) | OR (95% CI) | |
Parity | |||||||||
Nullipara | 291 (2.3) | 144 (1.1) | 1.35 (1.06, 1.69) | 152 (2.4) | 94 (1.5) | 1.16 (0.86-1.59) | 139 (2.12) | 50 (0.8) | 1.72 (1.18, 2.50) |
Para | 12 598 (97.7) | 12 745 (98.9) | 1.00 (reference) | 6170 (97.6) | 6228 (98.5) | 1.00 (reference) | 6428 (97.9) | 6517 (99.2) | 1.00 (reference) |
No. of childbirths | |||||||||
0 | 291 (2.3) | 144 (1.1) | 1.00 (reference) | 152 (2.4) | 94 (1.5) | 1.00 (reference) | 139 (2.1) | 50 (0.8) | 1.00 (reference) |
1 | 2046 (15.9) | 1370 (10.6) | 0.88 (0.69, 1.14) | 1200 (19.0) | 853 (13.5) | 1.01 (0.74, 1.39) | 846 (12.9) | 517 (7.9) | 0.72 (0.48, 1.06) |
2 | 7461 (57. 9) | 7552 (58.6) | 0.71 (0.61, 0.83) | 4248 (67.2) | 4526 (71.6) | 0.80 (0.65, 0.97) | 3213 (48.9) | 3026 (46.1) | 0.58 (0.45, 0.74) |
3+ | 3091 (24.0) | 3823 (29.7) | 0.62 (0.54, 0.80) | 722 (11.4) | 849 (13.4) | 0.81 (0.70, 0.94)1 | 2369 (36.1) | 2974 (45.3) | 0.40 (0.35, 0.43)1 |
Breastfeeding | |||||||||
No children | 291 (2.3) | 144 (1.1) | 1.38 (1.10, 1.75) | 152 (2.4) | 94 (1.5) | 1.17 (0.86, 1.58) | 139 (2.1) | 50 (0.8) | 1.80 (1.24, 2.62) |
Never | 2966 (23.0) | 1975 (15.3) | 1.00 (reference) | 1945 (30.8) | 1340 (21.2) | 1.00 (reference) | 1021 (15.6) | 635 (9. 7) | 1.00 (reference) |
Ever | 9632 (74.7) | 10 770 (83.6) | 0.60 (0.55, 0.64) | 4225 (66.8) | 4888 (77.3) | 0.59 (0.54, 0.65) | 5407 (82.3) | 5882 (89.6) | 0.60 (0.53, 0.68) |
Breastfeeding duration (mo) | |||||||||
0 | 3257 (25.3) | 2119 (16.4) | 1.00 (reference) | 2097 (33.2) | 1434 (22.7) | 1.00 (reference) | 1160 (17.7) | 685 (10.4) | 1.00 (reference) |
1-12 | 4116 (31.9) | 3624 (28.1) | 0.77 (0.71, 0.84) | 2372 (37.5) | 2470 (39.1) | 0.67 (0.60, 0.74) |
1744 (26.6) | 1154 (17.6) | 0.99 (0.86, 1.14) |
13-24 | 2901 (22.5) | 3576 (27.7) | 0.57 (0.52, 0.62) | 1293 (20.5) | 1711 (27.1) | 0.55 (0.48, 0.62) | 1608 (24.5) | 1865 (28.4) | 0.60 (0.52, 0.70) |
25+ | 1973 (15.3) | 3002 (23.3) | 0.41 (0.37, 0.46) | 398 (6.3) | 599 (9.5) | 0.44 (0.37, 0.53) | 1575 (24.0) | 2403 (36.6) | 0.44 (0.38, 0.52) |
Total women |
Premenopausal women |
Postmenopausal women |
||||
---|---|---|---|---|---|---|
HR+ | HR- | HR+ | HR- | HR+ | HR- | |
No. of childbirths | ||||||
0 | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) |
1 | 0.78 (0.61, 0.99) | 1.25 (0.87, 1.79) | 0.94 (0.69, 1.30) |
1.64 (0.96, 2.78) |
0.57 (0.39, 0.85) |
0.88 (0.53, 1.47) |
2 | 0.52 (0.44, 0.60) |
1.04 (0.83, 1.30) |
0.62 (0.50, 0.78) |
1.31 (0.92, 1.86) |
0.48 (0.37, 0.61) |
0.78 (0.57, 1.07) |
3+ | 0.39 (0.34, 0.46) |
1.05 (0.86, 1.18) |
0.55 (0.48, 0.61) |
1.39 (0.99, 1.83) |
0.22 (0.18, 0.25) |
0.73 (0.57, 0.99) |
Breastfeeding duration (mo) | ||||||
0 | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) |
1-12 | 0.74 (0.69, 0.80) | 0.77 (0.68, 0.87) | 0.67 (0.61, 0.73) |
0.65 (0.55, 0.77) |
1.03 (0.89, 1.20) |
0.94 (0.78, 1.13) |
13-24 | 0.52 (0.48, 0.57) | 0.52 (0.46, 0.60) | 0.53 (0.48, 0.59) | 0.48 (0.39, 0.58) | 0.64 (0.55, 0.74) | 0.55 (0.46, 0.67) |
25+ | 0.40 (0.37, 0.44) | 0.40 (0.34, 0.47) | 0.45 (0.38, 0.52) | 0.49 (0.37, 0.66) | 0.48 (0.41, 0.57) | 0.40 (0.32, 0.49) |
Total women |
Premenopausal women |
Postmenopausal women |
||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Luminal A | Luminal B | HER2-enriched | Triple-negative | Luminal A | Luminal B | HER2-enriched | Triple-negative | Luminal A | Luminal B | HER2-enriched | Triple-negative | |
No. of childbirths | ||||||||||||
0 | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) |
1 | 0.72 (0.58, 0.88) |
0.87 (0.55, 1.25) |
1.43 (0.83, 2.38) |
1.19 (0.78, 1.82) |
1.01 (0.72, 1.39) |
0.83 (0.49, 1.39) |
1.77 (0.81, 4.00) |
1.69 (0.90, 3.13) |
0.56 (0.37,0.83) |
0.85 (0.42, 1.72) |
1.06 (0.52, 2.17) |
0.80 (0.44, 1.45) |
2 | 0.45 (0.40, 0.51) |
0.80 (0.63, 1.03) |
1.23 (0.88, 1.74) |
0.96 (0.75, 1.25) |
0.63 (0.50, 0.79) |
0.88 (0.65, 1.17) |
1.38 (0.84, 2.36) |
1.41 (0.94, 2.09) |
0.36 (0.27, 0.47) |
0.74 (0.48, 1.16) |
1.04 (0.66, 1.65) |
0.64 (0.44, 0.91) |
3+ | 0.34 (0.30, 0.38) |
0.74 (0.61, 0.91) |
1.10 (0.83, 1.48) |
0.92 (0.73, 1.15) |
0.55 (0.46, 0.66) |
0.89 (0.72, 1.08) |
1.13 (1.08, 1.68) |
1.68 (1.21, 2.28) |
0.26 (0.20, 0.33) |
0.65 (0.44, 0.99) |
1.03 (0.68, 1.59) |
0.56 (0.40, 0.78) |
Breastfeeding duration (mo) | ||||||||||||
0 | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) |
1-12 | 0.73 (0.68, 0.79) | 0.80 (0.68, 0.92) | 0.84 (0.70, 0.99) | 0.71 (0.62, 0.83) | 0.67 (0.61, 0.74) |
0.69 (0.57, 0.83) |
0.68 (0.53, 0.87) |
0.61 (0.51, 0.75) |
0.87 (0.76, 0.99) |
1.00 (0.78, 1.28) |
1.00 (0.79, 1.27) |
0.88 (0.70, 1.11) |
13-24 | 0.51 (0.45, 0.55) | 0.63 (0.53, 0.74) | 0.50 (0.42, 0.61) | 0.52 (0.44, 0.61) | 0.51 (0.45, 0.57) | 0.65 (0.51, 0.87) | 0.50 (0.37, 0.67) | 0.45 (0.36, 0.57) | 0.50 (0.44, 0.57) | 0.60 (0.46, 0.77) | 0.48 (0.37, 0.63) | 0.59 (0.47, 0.75) |
25+ | 0.39 (0.36, 0.43) | 0.42 (0.34, 0.51) | 0.40 (0.32, 0.50) | 0.37 (0.31, 0.45) | 0.45 (0.38, 0.53) | 0.44 (0.31, 0.63) | 0.68 (0.44, 1.03) | 0.39 (0.27, 0.55) | 0.38 (0.33, 0.43) | 0.43 (0.33, 0.58) | 0.35 (0.27, 0.47) | 0.41 (0.32, 0.53) |
No. of childbirths | Breastfeeding duration (mo) | Premenopausal women | Postmenopausal women |
---|---|---|---|
0 | 0 | 1.00 (reference) | 1.00 (reference) |
1 | 0 | 0.98 (0.70, 1.39) | 0.65 (0.43, 0.99) |
2 | 0 | 0.78 (0.69, 0.92) | 0.63 (0.54, 0.73) |
3+ | 0 | 0.89 (0.86, 0.94) |
0.47 (0.44, 0.50) |
1 | 1-12 | 0.65 (0.58, 0.74) | 0.64 (0.55, 0.74) |
1 | 13-24 | 0.69 (0.51, 0.60) | 0.49 (0.42, 0.58) |
2 | 1-12 | 0.52 (0.45, 0.61) | 0.52 (0.43, 0.62) |
3+ | 1-12 | 0.63 (0.59, 0.68) | 0.70 (0.61, 0.80) |
2 | 13-24 | 0.44 (0.39, 0.51) | 0.36 (0.30, 0.44) |
2 | 25+ | 0.36 (0.34, 0.39) |
0.27 (0.23, 0.32) |
3+ | 13-24 | 0.36 (0.35, 0.38) |
0.29 (0.25, 0.33) |
3+ | 25+ | 0.34 (0.32, 0.38) |
0.21 (0.18, 0.26) |
The OR (95% CI) in all women was estimated in conditional logistic regression stratified by age and enrollment year and adjusted for family history of BC, age at menarche, age at first full-term pregnancy, duration of oral contraceptive use, BMI, and breastfeeding duration in the analyses of parity and number of childbirths; or adjusted for family history of BC, age at menarche, age at first full-term pregnancy, duration of oral contraceptive use, BMI, and number of childbirths in the analyses of breastfeeding and its duration. The OR (95% CI) in premenopausal and postmenopausal women was estimated in an unconditional logistic regression model stratified by age and year and adjusted for same covariates. BC, breast cancer; OR, odds ratio; CI, confidence interval; BMI, body mass index.
Values are presented as OR (95% CI). The OR (95% CI) in all women was estimated in conditional logistic regression stratified by age and enrollment year and adjusted for family history of BC, age at menarche, age at first full-term pregnancy, duration of oral contraceptive use, BMI, and breastfeeding duration in the analyses of parity and number of childbirths; or adjusted for family history of BC, age at menarche, age at first full-term pregnancy, duration of oral contraceptive use, BMI, and number of childbirths in the analyses of breastfeeding and its duration. HR, hormone receptor; BC, breast cancer; OR, odds ratio; CI, confidence interval; BMI, body mass index.
Values are presented as OR (95% CI). The OR (95% CI) in all women was estimated in conditional logistic regression stratified by age and enrollment year and adjusted for family history of BC, age at menarche, age at first full-term pregnancy, duration of oral contraceptive use, BMI, and breastfeeding duration in the analyses of parity and number of childbirths; or adjusted for family history of BC, age at menarche, age at first full-term pregnancy, duration of oral contraceptive use, BMI, and number of childbirths in the analyses of breastfeeding and its duration. HR, hormone receptor; BC, breast cancer; OR, odds ratio; CI, confidence interval; BMI, body mass index.
Values are presented as OR (95% CI). The OR (95% CI) in all women was estimated in conditional logistic regression stratified by age and enrollment year and adjusted for family history of BC, age at menarche, age at first full-term pregnancy, duration of oral contraceptive use, BMI, and breastfeeding duration in the analyses of parity and number of childbirths; or adjusted for family history of BC, age at menarche, age at first full-term pregnancy, duration of oral contraceptive use, BMI, and number of childbirths in the analyses of breastfeeding and its duration. The calculated actual OR values in premenopausal and postmenopausal women was estimated using an unconditional logistic regression model stratified by age and year and adjusted for same covariates. BC, breast cancer, OR, odds ratio; CI, confidence interval; BMI, body mass index.