Table 4 Studies assessing the association of maternal age with risk for breast cancer

Case-control studies

[51]

1967

LCC-D

229

229

USA

≤ 19

Mean maternal age among cases was higher than that among controls (P < 0.005). The frequency of each case and control were shown in the tables provided and we calculated crude ORs

20–24

25–29

30–34

35–39

≥ 40

[61]^a

1974

PCC

308

308

USA

Matched analysis; the mean maternal age was 27.3 years among cases and 26.3 years among controls (P < 0.01)

[50]^b

1980

MCC

4339

12760

USA, Japan, Slovenia, Athens, Taipei

≤ 19

Referent

Authors showed point estimates of ORs without 95% CIs. The frequencies for each case and control were given in the tables provided and we calculated crude ORs

20–24

1.05

25–29

1.22

30–34

1.19

35–39

1.31

≥ 40

1.18

[53]^a

1984

MCC

1,176

1,176

England

≤ 20

Referent

Adjusted for age, social class, family history of breast cancer, age at first-term birth, past history of benign breast disease, age at menarche, menopausal status, cigarette smoking, and oral contraceptive use

21–25

1.41 (0.92–2.18)

26–30

1.19 (0.78–1.81)

31–35

1.29 (0.83–1.98)

≥ 36

1.19 (0.68–1.67)

[42]^a

1988

PCC

153

461

USA

All women

Matched analysis

   15–22

1.18 (0.71–1.97)

   23–26

Referent

   27–30

1.22 (0.71–2.10)

   31–46

1.66 (0.99–2.78)

P for trend = 0.67

Younger women

   15–23

1.39 (0.65–2.95)

   24–28

Referent

   29–46

2.21 (1.02–4.80)

P for trend = 0.08

[52]^a

1989

PCC

801

1,573

USA

Continuous

1.24 (1.09–1.41)

Crude OR

[54]

1990

PCC

2,291

3,144

USA

≤ 19

Referent

Adjusted for age and parity, age at first pregnancy, total duration of breast feeding, race, age at menarche, menopausal status, body mass index, family history of breast cancer, and breast biopsy

20–24

0.95 (0.77–1.16)

25–29

1.13 (0.92–1.38)

30–34

1.16 (0.93–1.45)

35–39

1.46 (1.10–1.93)

≥ 40

1.20 (0.79–1.83)

[55]

1991

PCC

1761

1,116,553 person-years

USA

≤ 19

Referent

Crude ORs

20–24

1.02 (0.82–1.46)

25–29

1.12 (1.04–1.38)

30–34

1.16 (0.93–1.44)

35–39

1.17 (0.92–1.48)

≥ 40

1.08 (0.80–1.46)

[46]^a

1991

MCC

927

2616

USA, Wales, Japan

Each 5-yrs

1.06 (1.01–1.10)

Adjusted for age, study center, parity, age at first birth, age at menarche, height, BMI, maternal age at birth, and menopausal status

[12]^b

1992

LCC

458

1,197

Sweden

Each 5-year band

1.01 (0.92–1.12)

Adjusted for age and birth date. The authors estimated breast cancer risk according to each 5-year band of maternal age. The frequency of each case and control were given in the tables provided and we calculated crude ORs

[47]

1994

PCC

2,412

9,138

USA

≤ 19

Referent

Adjusted for age at first birth and number of children

20–24

1.05 (0.85–1.30)

25–29

1.10 (0.89–1.37)

30–34

1.10 (0.88–1.37)

35–39

1.09 (0.87–1.37)

≥ 40

0.99 (0.76–1.28)

[14]

1996

PCC

1,934

2,161

USA

≤ 24

Referent

Adjusted for age, menopausal status, and maternal smoking

25–29

1.0 (0.8–1.2)

30–34

0.9 (0.6–1.1)

≥ 35

1.0 (0.7–1.5)

[57]

1997

PCC

1,253

1,121

USA

≤ 19

Referent

Adjusted for age, menopausal status, age at menarche, parity, age at first birth, body mass index, past history of benign breast disease, and recent alcohol intake

20–24

0.84 (0.62–1.14)

25–29

1.02 (0.76–1.37)

30–34

0.93 (0.68–1.28)

35–39

1.16 (0.82–1.65)

≥ 40

0.92 (0.62–1.37)

[58]

1997

PCC

2,106

1,926

USA

≤ 19

Referent

Adjusted for age, study site, family history of breast cancer, breast biopsy, a combination variable including number of full-term births and age at first full-term pregnancy, age at menarche, menopausal status, body mass index, average lifetime alcohol consumption, and the number of mammograms

20–24

0.96 (0.7–1.2)

25–29

0.96 (0.7–1.2)

30–34

0.91 (0.7–1.2)

≥ 35

0.93 (0.7–1.3)

[32]^a

1997

NCC

1,067

2,725

Sweden

Each 5-year band

1.06 (0.99–1.14)

Adjusted for maternal age, socioeconomic status, parity, and pre-eclampsia or eclampsia, neonatal jaundice, severe prematurity, and twinship

[15]

2000

LCC

481

2863

USA

≤ 19

1.19 (0.83–1.72)

Crude ORs

20–24

Referent

25–29

1.26 (0.97–1.64)

30–34

1.38 (1.04–1.84)

≥ 35

1.70 (1.23–2.35)

[35]

2002

PCC

1,555

1,539

USA

≤ 19

1.02 (0.75–1.39)

Adjusted for age and state

20–24

0.98 (0.81–1.18)

25–29

Referent

30–34

1.15 (0.93–1.42)

35–39

1.22 (0.94–1.58)

≥ 40

1.27 (0.90–1.69)

[18]

2003

LCC

881

3,423

Denmark

≤ 24

Referent

Adjusted for mother's marital status, maternal age, and birth order

25–29

1.08 (0.88–1.32)

≥ 30

1.11 (0.90–1.36)

[36]^a

2004

PCC

854

785

USA

≤ 18

1.8 (0.9–3.4)

19–22

Referent

Adjusted for age, race and sampling fractions; tertiles are race specific with cutpoints derived from controls

23–27

3.0 (1.8–5.0)

≥ 28

2.5 (1.6–4.0)

[56]

2005

MCC

1,060

1,060

Korea

≤ 24

Referent

Adjusted for age, family history of breast cancer in first-or second-degree relatives, menopausal status, and lifetime estrogen exposure duration

25–29

1.2 (0.93–1.47)

30–34

1.4 (1.12–1.83)

≥ 35

1.1 (0.83–1.37)

[20]

2006

PCC

1,642

1,713

Poland

≤ 19

Referent

Adjusted for: age, education, age at menarche, menopausal status and age at menopause, age at first full-term pregnancy, number of full-term pregnancies, family history of breast cancer among first-degree relatives, mammography screening, and current body mass index

20–24

1.02 (0.75–1.39)

25–29

1.07 (0.79–1.46)

35–39

1.16 (0.84–1.60)

≥ 35

0.91 (0.66–1.27)

P for trend = 0.76

[37]^a

2006

PCC

1,166

2,105

USA

≤ 24

Referent

Adjusted for: age, education, race, body mass index, history of breast benign disease, family history of breast cancer, lactation, age at menarche, age at first full-term pregnancy, age at menopause, and parity

25–35

0.87 (0.67–1.13)

>35

0.87 (0.59–1.27)

Cohort studies

[59]

1995

Cohort

149

75,237

USA

≤ 24

Referent

Adjusted for age, education, menopausal status, parity, body mass index, height, smoking, and alcohol drinking

25–29

1.3 (0.8–2.0)

30–34

1.4 (0.9–2.1)

≥ 35

1.2 (0.7–2.0)

[60]

1995

Cohort

1,967

384,769

Sweden

≤ 19

Referent

Breast cancer mortality; adjusted for age

20–24

0.99 (0.82–1.21)

25–29

1.00 (0.82–1.22)

30–34

0.97 (0.79–1.18)

35–39

1.04 (0.84–1.29)

40–44

0.93 (0.71–1.21)

≥ 45

1.39 (0.91–2.13)

[49]^a

2001

Cohort

Sweden

Continuous scale

1.07 (0.91–1.27)

Adjusted for spouse age, year of diagnosis, and birth order

[38]^a

2001

Cohort

177

3,447

Filand

Continuous scale

-

No association

[31]

2006

Cohort

249

1,024

USA

≤ 24

Referent

Hazard ratio; adjusted for age at diagnosis, diagnosis year, stage at diagnosis, and birth order, with exception of birth order, which is adjusted for maternal age

25–29

1.2 (0.9–1.7)

30–34

1.4 (0.9–1.9)

≥ 35

1.7 (1.1–2.8)

P for trend = 0.03