Breastfeeding and cancer: the Boyd Orr cohort and a systematic review with meta-analysis
Journal
JNCI Journal of the National Cancer Institute
Date Issued
2005
DOI
10.1093/jnci/dji291
Abstract
Background: Having been breast-fed has been suggested to
infl uence cancer risk in adulthood. We investigated associations
between breast-feeding during infancy and adult
cancer incidence and mortality in a cohort study and metaanalyses
of published studies. Methods: The Boyd Orr cohort
consisted of 4999 subjects who were originally surveyed
in 1937 – 39, when they were 0 – 19 years of age. Cancer outcomes
from 1948 through 2003 were available for 4379 (88%)
subjects, and 3844 had complete data on all covariates. Associations
of breast-feeding with cancer were investigated
using proportional hazards models. We also identifi ed 14
studies on infant feeding and cancer published from 1966
through July 2005, of which 10 could be combined with the
Boyd Orr cohort results in a meta-analysis of breast cancer
using random-effect models. Results: In the Boyd Orr
cohort, ever having been breast-fed, compared with never
having been breast-fed, was not associated with the incidence
of all cancers (hazard ratio [HR] = 1.07, 95% confi dence interval
[CI] = 0.89 to 1.28) or of any individual cancer type
examined (prostate HR = 1.43, 95% CI = 0.58 to 3.52; breast
HR = 1.62, 95% CI = 0.89 to 2.94; colorectal HR = 0.86, 95%
CI = 0.45 to 1.63; gastric HR = 1.22, 95% CI = 0.47 to 3.15).
In the meta-analysis, there was also no association between
breast-feeding and breast cancer (regardless of menopausal
status) (relative risk [RR] = 0.94, 95% CI = 0.85 to 1.04).
However, breast-fed women had a reduced risk of premenopausal
breast cancer (RR = 0.88, 95% CI = 0.79 to 0.98) but
not of postmenopausal breast cancer (RR = 1.00, 95% CI =
0.86 to 1.16). Conclusion: Ever having been breast-fed was
not associated with overall breast cancer risk, although the
meta-analysis revealed a reduced risk of premenopausal
breast cancer in women who had been breast-fed. [J Natl
Cancer Inst 2005;97:1446 – 57]
infl uence cancer risk in adulthood. We investigated associations
between breast-feeding during infancy and adult
cancer incidence and mortality in a cohort study and metaanalyses
of published studies. Methods: The Boyd Orr cohort
consisted of 4999 subjects who were originally surveyed
in 1937 – 39, when they were 0 – 19 years of age. Cancer outcomes
from 1948 through 2003 were available for 4379 (88%)
subjects, and 3844 had complete data on all covariates. Associations
of breast-feeding with cancer were investigated
using proportional hazards models. We also identifi ed 14
studies on infant feeding and cancer published from 1966
through July 2005, of which 10 could be combined with the
Boyd Orr cohort results in a meta-analysis of breast cancer
using random-effect models. Results: In the Boyd Orr
cohort, ever having been breast-fed, compared with never
having been breast-fed, was not associated with the incidence
of all cancers (hazard ratio [HR] = 1.07, 95% confi dence interval
[CI] = 0.89 to 1.28) or of any individual cancer type
examined (prostate HR = 1.43, 95% CI = 0.58 to 3.52; breast
HR = 1.62, 95% CI = 0.89 to 2.94; colorectal HR = 0.86, 95%
CI = 0.45 to 1.63; gastric HR = 1.22, 95% CI = 0.47 to 3.15).
In the meta-analysis, there was also no association between
breast-feeding and breast cancer (regardless of menopausal
status) (relative risk [RR] = 0.94, 95% CI = 0.85 to 1.04).
However, breast-fed women had a reduced risk of premenopausal
breast cancer (RR = 0.88, 95% CI = 0.79 to 0.98) but
not of postmenopausal breast cancer (RR = 1.00, 95% CI =
0.86 to 1.16). Conclusion: Ever having been breast-fed was
not associated with overall breast cancer risk, although the
meta-analysis revealed a reduced risk of premenopausal
breast cancer in women who had been breast-fed. [J Natl
Cancer Inst 2005;97:1446 – 57]
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