The independent associations of parity, age at first full term pregnancy, and duration of breastfeeding with the risk of breast cancer

Layde, Peter M.; Webster, Linda A.; Baughman, Andrew L.; Wingo, Phyllis A.; Rubin, George; Ory, Howard W.

doi:10.1016/0895-4356(89)90161-3

Cited by 229 publications

(115 citation statements)

References 26 publications

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“…The findings of inverse dose-response relationship with duration of breastfeeding in premenopausal women are in accordance with those from previous studies [14][15][16][17][18][19][20][21][22] and one large pooled analysis. 5 Breastfeeding for long duration was common in the study population and only less than 2% did not breastfeed, whereas in most Western countries, the prevalence of prolonged breastfeeding tends to be low because majority of women have relatively few children, and the average duration of breastfeeding per child is shorter.…”

Section: Discussionsupporting

confidence: 81%

Breastfeeding and breast cancer risk in India: A multicenter case‐control study

Gajalakshmi

Mathew

Brennan

et al. 2009

Intl Journal of Cancer

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Breast cancer incidence is low in India compared with highincome countries, but it has increased in recent decades, particularly among urban women. The reasons for this pattern are not known although they are likely related to reproductive and lifestyle factors. Here, we report the results of a large case-control study on the association between breastfeeding and breast cancer risk. The study was conducted in 2 areas in South India during [2002][2003][2004][2005] and included 1,866 cases and 1,873 controls. Detailed information regarding menstruation, reproduction, breastfeeding and physical activity was collected through in-person interview. Odds ratios (OR) and 95% confidence intervals (CI) were estimated by unconditional logistic regression models. Breastfeeding for long duration was common in the study population. Lifetime duration of breastfeeding was inversely associated with breast cancer risk among premenopausal women (p-value of linear trend, 0.02). No such protective effect was observed in postmenopausal women, among whom a protective effect of parity was suggested. A reduction of breast cancer risk with prolonged breastfeeding was shown among premenopausal women. Health campaign focusing on breastfeeding behavior by appropriately educating women would contribute to reduce breast cancer burden. ' UICCKey words: breastfeeding; breast cancer; India Breast cancer is the most common cancer in women worldwide with nearly 1,000,000 new cases each year, representing over 20% of all malignancies. 1 There are striking geographic variations in breast cancer incidence with more than a 10-fold difference between low rates in rural African and Asian populations and high rates in North American and Western European populations.Age-standardized breast cancer incidence rates in India range from 15 to 29 per 100,000 and have been increasing in recent decades, especially among urban women, and India is now the country with the largest estimated number of breast cancer deaths worldwide. 1 The reasons for the low incidence of breast cancer among Indian women and the increasing incidence in recent years are not completely understood, although are likely to be explained by reproductive and lifestyle factors. Only few epidemiological studies have been conducted to determine the risk factors of breast cancer in Indian women. [2][3][4] Although it is well established that prolonged breastfeeding decreases the risk of breast cancer, 5 most of the evidence derives from studies conducted in high-income countries. Data from lowincome countries, where prolonged breastfeeding is prevalent, are needed to better quantify the effect of long-term breastfeeding.The World Health Organization (WHO) 6 conducted a study on breastfeeding in India between 1975 and 1978, and found sociocultural factors such as education, employment and income to be the strongest determinants of the length of breastfeeding; 96% of mothers in the urban areas and 100% in rural areas breastfed their infants. Data from National Family Health Survey-2 show that in ...

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Section: Discussionsupporting

confidence: 81%

Breastfeeding and breast cancer risk in India: A multicenter case‐control study

Gajalakshmi

Mathew

Brennan

et al. 2009

Intl Journal of Cancer

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“…Young age at first birth and increasing parity are established protective factors in breast cancer risk (La Vecchia et al, 1989;Layde et al, 1989;Lambe et al, 1996;Merrill et al, 2005). In this study, after adjusting for other study variables, age at first birth and parity were significant factors in GM women aged 50 þ years.…”

Section: Discussionmentioning

confidence: 78%

Birth intervals and breast cancer risk

et al. 2009

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BACKGROUND: The interval between successive births (birth interval) may affect breast cancer risk, whereas interval from last birth to cancer onset may modify its behaviour. METHODS: The study cohort consisted of 29 488 Finnish grand multiparous (GM) women, including 628 women with breast cancer. Conditional logistic regression for case -control design nested within the cohort was used to estimate proportional hazards (referred as relative risks, RR). Age at first birth and parity were co-variables. RESULTS: Short interval (o1 year) between first and second birth increased the risk of advanced ductal breast cancer at ages o 50 years (RR ¼ 5.29; 95% CI 2.00 -14.0) as compared to interval 3 þ years. The risk of advanced ductal cancer was also large (RR ¼ 4.00; 95% CI 1.19 -13.4) shortly (o3 years) after last birth as compared with the period 15 þ years. CONCLUSIONS: Short birth interval-associated excess breast cancer risk may be related to stimulatory effects of female steroid hormones produced during two closely connected pregnancies, or defective breast maturation owing to failures in breastfeeding.

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“…Among case-control studies that have found a protective effect the reported odds ratios for ever vs never breastfeeding among parous women range from 0.6 to slightly below 1.0 (Byers et al, 1985;McTiernan and Thomas, 1986;Tao et al 1988;Layde et al, 1989;Siskind et al, 1989;Adami et al, 1990;Yoo et al, 1992;Thomas et al, 1993;Yang et al, 1993;Newcomb et al, 1994). In most of these studies the apparently protective effect was stronger among, or limited to, premenopausal women (Byers et al, 1985;McTiernan and Thomas, 1986;Thomas et al, 1993;Yang et al, 1993;Newcomb et al, 1994).…”

Section: Discussionmentioning

confidence: 99%