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Birth size and breast cancer risk: re-analysis of individual participant data from 32 studies.

Silva Idos S, De Stavola B, McCormack V, Collaborative Group on Pre-Natal Risk Factors and Subsequent Risk of Breast Canc - PLoS Med. (2008)

Bottom Line: Random effect models were used, if appropriate, to combine study-specific estimates of effect.Simultaneous adjustment for these three birth size variables showed that length was the strongest independent predictor of risk.The birth size effects did not appear to be confounded or mediated by established breast cancer risk factors and were not modified by age or menopausal status.

View Article: PubMed Central - PubMed

Affiliation: Department of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, UK. isabel.silva@lshtm.ac.uk

ABSTRACT

Background: Birth size, perhaps a proxy for prenatal environment, might be a correlate of subsequent breast cancer risk, but findings from epidemiological studies have been inconsistent. We re-analysed individual participant data from published and unpublished studies to obtain more precise estimates of the magnitude and shape of the birth size-breast cancer association.

Methods and findings: Studies were identified through computer-assisted and manual searches, and personal communication with investigators. Individual participant data from 32 studies, comprising 22,058 breast cancer cases, were obtained. Random effect models were used, if appropriate, to combine study-specific estimates of effect. Birth weight was positively associated with breast cancer risk in studies based on birth records (pooled relative risk [RR] per one standard deviation [SD] [= 0.5 kg] increment in birth weight: 1.06; 95% confidence interval [CI] 1.02-1.09) and parental recall when the participants were children (1.02; 95% CI 0.99-1.05), but not in those based on adult self-reports, or maternal recall during the woman's adulthood (0.98; 95% CI 0.95-1.01) (p for heterogeneity between data sources = 0.003). Relative to women who weighed 3.000-3.499 kg, the risk was 0.96 (CI 0.80-1.16) in those who weighed < 2.500 kg, and 1.12 (95% CI 1.00-1.25) in those who weighed > or = 4.000 kg (p for linear trend = 0.001) in birth record data. Birth length and head circumference from birth records were also positively associated with breast cancer risk (pooled RR per one SD increment: 1.06 [95% CI 1.03-1.10] and 1.09 [95% CI 1.03-1.15], respectively). Simultaneous adjustment for these three birth size variables showed that length was the strongest independent predictor of risk. The birth size effects did not appear to be confounded or mediated by established breast cancer risk factors and were not modified by age or menopausal status. The cumulative incidence of breast cancer per 100 women by age 80 y in the study populations was estimated to be 10.0, 10.0, 10.4, and 11.5 in those who were, respectively, in the bottom, second, third, and top fourths of the birth length distribution.

Conclusions: This pooled analysis of individual participant data is consistent with birth size, and in particular birth length, being an independent correlate of breast cancer risk in adulthood.

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Minimally Adjusted Pooled Breast Cancer RRs in Relation to Continuous Weight, Length, PI, and Head Circumference at Birth Stratified by Age (Restricted to Singleton Studies Based on Birth Records)
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pmed-0050193-g007: Minimally Adjusted Pooled Breast Cancer RRs in Relation to Continuous Weight, Length, PI, and Head Circumference at Birth Stratified by Age (Restricted to Singleton Studies Based on Birth Records)

Mentions: The effect of categorical (Figure S8; study-specific estimates available in Table S8) or continuous birth weight (Figure 7) was not modified by age (defined as current age for cohort studies and age at diagnosis for case-control studies). There was also no evidence of any interaction between age and continuous birth length, PI, or head circumference (Figure 7). Menopausal status was known for 33% of the cases, but analysis restricted to the subset of studies with this information showed no difference in the birth size effects between pre- and postmenopausal women.


Birth size and breast cancer risk: re-analysis of individual participant data from 32 studies.

Silva Idos S, De Stavola B, McCormack V, Collaborative Group on Pre-Natal Risk Factors and Subsequent Risk of Breast Canc - PLoS Med. (2008)

Minimally Adjusted Pooled Breast Cancer RRs in Relation to Continuous Weight, Length, PI, and Head Circumference at Birth Stratified by Age (Restricted to Singleton Studies Based on Birth Records)
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2553821&req=5

pmed-0050193-g007: Minimally Adjusted Pooled Breast Cancer RRs in Relation to Continuous Weight, Length, PI, and Head Circumference at Birth Stratified by Age (Restricted to Singleton Studies Based on Birth Records)
Mentions: The effect of categorical (Figure S8; study-specific estimates available in Table S8) or continuous birth weight (Figure 7) was not modified by age (defined as current age for cohort studies and age at diagnosis for case-control studies). There was also no evidence of any interaction between age and continuous birth length, PI, or head circumference (Figure 7). Menopausal status was known for 33% of the cases, but analysis restricted to the subset of studies with this information showed no difference in the birth size effects between pre- and postmenopausal women.

Bottom Line: Random effect models were used, if appropriate, to combine study-specific estimates of effect.Simultaneous adjustment for these three birth size variables showed that length was the strongest independent predictor of risk.The birth size effects did not appear to be confounded or mediated by established breast cancer risk factors and were not modified by age or menopausal status.

View Article: PubMed Central - PubMed

Affiliation: Department of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, UK. isabel.silva@lshtm.ac.uk

ABSTRACT

Background: Birth size, perhaps a proxy for prenatal environment, might be a correlate of subsequent breast cancer risk, but findings from epidemiological studies have been inconsistent. We re-analysed individual participant data from published and unpublished studies to obtain more precise estimates of the magnitude and shape of the birth size-breast cancer association.

Methods and findings: Studies were identified through computer-assisted and manual searches, and personal communication with investigators. Individual participant data from 32 studies, comprising 22,058 breast cancer cases, were obtained. Random effect models were used, if appropriate, to combine study-specific estimates of effect. Birth weight was positively associated with breast cancer risk in studies based on birth records (pooled relative risk [RR] per one standard deviation [SD] [= 0.5 kg] increment in birth weight: 1.06; 95% confidence interval [CI] 1.02-1.09) and parental recall when the participants were children (1.02; 95% CI 0.99-1.05), but not in those based on adult self-reports, or maternal recall during the woman's adulthood (0.98; 95% CI 0.95-1.01) (p for heterogeneity between data sources = 0.003). Relative to women who weighed 3.000-3.499 kg, the risk was 0.96 (CI 0.80-1.16) in those who weighed < 2.500 kg, and 1.12 (95% CI 1.00-1.25) in those who weighed > or = 4.000 kg (p for linear trend = 0.001) in birth record data. Birth length and head circumference from birth records were also positively associated with breast cancer risk (pooled RR per one SD increment: 1.06 [95% CI 1.03-1.10] and 1.09 [95% CI 1.03-1.15], respectively). Simultaneous adjustment for these three birth size variables showed that length was the strongest independent predictor of risk. The birth size effects did not appear to be confounded or mediated by established breast cancer risk factors and were not modified by age or menopausal status. The cumulative incidence of breast cancer per 100 women by age 80 y in the study populations was estimated to be 10.0, 10.0, 10.4, and 11.5 in those who were, respectively, in the bottom, second, third, and top fourths of the birth length distribution.

Conclusions: This pooled analysis of individual participant data is consistent with birth size, and in particular birth length, being an independent correlate of breast cancer risk in adulthood.

Show MeSH
Related in: MedlinePlus