Age at first birth, parity and risk of breast cancer: A meta‐analysis of 8 studies from the nordic countries

Ewertz, Marianne; Duffy, Stephen W.; Adami, Hans‐Olov; Kvåle, Gunnar; Lund, Eiliv; Meirik, Olav; Mellemgaard, Anders; Soini, Irma; Tulinius, Hrafn

doi:10.1002/ijc.2910460408

Cited by 232 publications

(169 citation statements)

References 27 publications

(33 reference statements)

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“…Although some studies have not supported this observation (Mohle Boetani et al, 1988;Lees et al, 1989;Ewertz et al, 1991), there is accumulating evidence that does support it (Greenberg et al, 1985;Kogevinas, 1990;Schouten et al, 1997 (MacMahon et al, 1970;Ewertz et al, 1990 (Ewertz et al, 1990).…”

Section: Discussionmentioning

confidence: 99%

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Parity, age at first childbirth and the prognosis of primary breast cancer

Kroman

Wohlfahrt²,

Andersen³

et al. 1998

Br J Cancer

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Summary Reproductive factors are known to be aetiologically important in breast cancer, but less is known regarding their effect on breast cancer prognosis. We have investigated the prognostic effect of age at first birth and total parity using data from the Danish Breast Cancer Cooperative Group that, since 1977, has collected population-based information on tumour characteristics, treatment regimes and follow-up status on Danish women with breast cancer. Details of pregnancy history were added from the Danish Civil Registration System and the National Birth Registry. Included in the study were 10 703 women with primary breast cancer. After adjusting for age and stage of disease (tumour size, axillary nodal status and histological grading), the number of full-term pregnancies was found without prognostic value. However, women with primary childbirth between 20 and 29 years experienced a significantly reduced risk of death compared with women with primary childbirth below the age of 20 years [20-24 years: relative risk (RR) = 0.88, 95% confidence interval (Cl) 0.78-0.99; 25-29 years: RR = 0.80, 95% Cl 0.70-0.91]. Further adjustment for oestrogen receptor status did not influence these results. The effect was not modified by age at diagnosis, tumour size or nodal status. In conclusion, low age at first childbirth, but not parity, was associated with a poor prognosis of breast cancer. We speculate whether women who develop breast cancer despite an early first full-term pregnancy might represent a selected group with a more malignant disease.

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Section: Discussionmentioning

confidence: 99%

“…Parous women and in particular multiparous women are known to be at a lower risk of breast cancer than nulliparous women. Women having their first childbirth at a young age seem to experience a particular reduction in risk (MacMahon et al, 1970;Ewertz et al, 1990).…”

mentioning

confidence: 99%

Parity, age at first childbirth and the prognosis of primary breast cancer

Kroman

Wohlfahrt²,

Andersen³

et al. 1998

Br J Cancer

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“…This method allows the point and interval estimates of relative risks to be obtained and provides tests of the effects on risk and of heterogeneity from study to study. Mathematical details are given elsewhere (Ewertz et al, 1990;Woolf, 1955). The interaction was tested as the statistical significance of the weighted average of the interaction terms using a 0.05 level of significance.…”

Section: Methodsmentioning

confidence: 99%

The effects of interaction between familial and reproductive factors on breast cancer risk: a combined analysis of seven case-control studies

Andrieu

Smith²,

Duffy³

et al. 1998

Br J Cancer

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Summary In this paper, a combined analysis was performed to study the interaction between familial risk and reproductive life factors. In particular, the interaction between familial risk and breast cell mitotic activity (BCMA), as assessed by duration of ovarian activity, was investigated because of the potential importance of mitotic activity on genetically susceptible cells. The present analysis included 3152 cases and 4404 controls in seven case-control studies from four countries. The interaction effect was estimated in each study separately, then combined using two different methods: a multivariate weighted average and a Bayesian random-effects model. The main effects of reproductive life factors on the risk of breast cancer were in agreement with the previous findings. In particular, an increased duration of BCMA before the first childbirth and over life was found to increase the risk of breast cancer (P < 0.001). Slightly increasing but nonsignificant, familial risks were observed with increasing number of children (P= 0.17), increasing age at first childbirth (P> 0.2) and increasing duration of BCMA (P > 0.2). There was no modification in familial risk with age at menarche and no clear pattern with menopause characteristics. A weak influence of reproductive and menstrual factors on the familial risk emerged from the present study.

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“…According to numerous case-control studies, low parity, older age at the time of birth of the first child, and high socioeconomic status (SES) are established risk factors for breast cancer [4][5][6] for women aged 40 to 49 years, although the association between SES and breast cancer appears to be more pronounced for older/postmenopausal women. [7][8][9] Women with high SES who are diagnosed with breast cancer may have a better survival than women with low SES 10,11 and breast cancer survival appears worse among young/premenopausal and nulliparous women.…”

Section: Introductionmentioning

confidence: 99%

Effectiveness of population‐based service screening with mammography for women ages 40 to 49 years with a high or low risk of breast cancer: Socioeconomic status, parity, and age at birth of first child

Hellquist

Czene

Hjälm

et al. 2014

Cancer

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BACKGROUND: Invitation to mammography screening of women aged 40 to 49 years is a matter of debate in many countries and a cost-effective alternative in countries without screening among women aged 40 to 49 years could be inviting those at higher risk. The relative effectiveness of mammography screening was estimated for subgroups based on the breast cancer risk factors parity, age at time of birth of first child, and socioeconomic status (SES). METHODS: The SCReening of Young Women (SCRY) database consists of all women aged 40 to 49 years in Sweden between 1986 and 2005 and was split into a study and control group. The study group consisted of women residing in areas in which women aged 40 to 49 years were invited to screening and the control group of women in areas in which women aged 40 to 49 years were not invited to screening. Rate ratio (RR) estimates were calculated for 2 exposures: invitation and attendance. RESULTS: There were striking similarities noted in the RR pattern for women invited to and attending screening and no statistically significant difference or trend in the RR was noted by risk group. The RR estimates increased by increasing parity for parity of 0 to 2 and ranged from 0.55 (95% confidence interval [95% CI], 0.38-0.79) to 0.79 (95% CI, 0.65-0.95) for attending women. The RR for women with high SES was lower than that for women with low SES (RR, 0.72 [95% CI, 0.79 [95% CI,], respectively). For women aged 20 to 24 years at the time of the birth of their first child, the RR was 0.73 (95% CI, 0.58-0.91) and estimates for other ages were similar. CONCLUSIONS: There was no statistically significant difference noted in the relative effectiveness of mammography screening by parity, age at the time of birth of the first child, or SES. Cancer 2015;121:251-8.

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Age at first birth, parity and risk of breast cancer: A meta‐analysis of 8 studies from the nordic countries

Cited by 232 publications

References 27 publications

Parity, age at first childbirth and the prognosis of primary breast cancer

Parity, age at first childbirth and the prognosis of primary breast cancer

The effects of interaction between familial and reproductive factors on breast cancer risk: a combined analysis of seven case-control studies

Effectiveness of population‐based service screening with mammography for women ages 40 to 49 years with a high or low risk of breast cancer: Socioeconomic status, parity, and age at birth of first child

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