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

From: Intrauterine environments and breast cancer risk: meta-analysis and systematic review

  Ref. Year Design Cases Controls (or cohort) Country/place of study Maternal age (years) OR (95% CI) Comments
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  
  1. aWe did not include these studies in the meta-analysis because they employed different categories or a continuous scale, or they did not provide the numbers of cases and controls in the original articlebWe included this study in the meta-analysis because we calculated the crude OR using the number of subjects represented the original article. Cohort, cohort study; LCC, case-control study with linkage with population and cancer registry data; LCC-D, case-control study with linkage with population and cancer death certification data; MCC, multicenter case-control study; NCC, nested case-control study in cohort; PCC, population-based case-control study.