Grant title: Childhood growth and body size across the lifecourse: pathways to breast cancer
> On the blog: Jennifer Baker explores her early findings on breast cancer and BMI
Background
Breast cancer has a complex association with overweight (including obesity). A high body mass index (BMI) in childhood as well as in early adulthood (before age 30 years), is associated with decreased risks of both pre-menopausal and post-menopausal breast cancer. In contrast, having overweight throughout adulthood, after menopause and/or weight gain in adulthood are associated with increased risks of post-menopausal breast cancer. The reasons for these opposing effects of overweight at different timepoints on breast cancer risks are under-explored. To better understand the associations of overweight across the life course with breast cancer, we conducted a series of studies.
Aims and objectives
The objectives were to examine how body size across the life course, with a special focus on the inter-related effects of birthweight, childhood height and BMI, pubertal timing, and body size at adult ages, were associated with benign breast disease (BBD), breast density and breast cancer.
Methods
We studied more than 160,000 Danish women born from 1930-1996, who underwent regular childhood school health examinations in Copenhagen. We used information on birthweight, measured weights and heights at ages 6-15 years and markers of pubertal timing. We used a unique identification number linked with national health and socioeconomic status registers and a variety of other data-resources to obtain information on BBD, breast density, breast cancer as well as adult body size and relevant covariates. We used a wide range of advanced statistical methods to construct trajectories of BMI across childhood ages and the life course, and to examine the associations of body size with the BBD, breast density and breast cancer.
Results
The results do not support a role of birthweight and pubertal timing in the development of breast cancer. In contrast, we provide evidence that childhood height is related to both pre- and post-menopausal breast cancer, because we found that the taller a girl was in childhood, the greater the risks. However, our results do not support a role of BBD nor breast density on the pathway between childhood height and breast cancer.
We found consistent evidence that the higher the BMI in childhood, the lower the risks of BBD, having dense breasts, and pre-menopausal and post-menopausal breast cancer. Thus, our results indicate that the effects of a high BMI in childhood on these outcomes may share a common pathway.
The importance of childhood adiposity was further highlighted when we examined patterns of BMI development across childhood ages and across the life course. Notably, our results indicate that, in addition to the level of adiposity in adulthood, the timing of developing excess adiposity across the life course also matters for risks of breast cancer.
Conclusions
Overall, these findings highlight the importance of considering a woman’s entire BMI trajectory, from birth through adulthood, when assessing breast cancer risk. Our results underpin the importance of including different indicators of early life body size and pubertal timing as well as applying a life course approach when examining effects of body size in relation to breast cancer development.
Impact
This project advanced our understanding of the role of early-life body size in relation to breast cancer, helping to unravel the complexities of these associations using some of the most well-suited data available globally. Together with future studies, this research has the potential to influence policies and public health initiatives aimed at improving children’s health.
Grant publications
- Pedersen, Dorthe C., et al. “Associations of Early Life Body Size and Pubertal Timing with Breast Density and Postmenopausal Breast Cancer Risk: A Mediation Analysis.” Annals of Epidemiology, vol. 102, 2025, pp. 68-74. https://doi.org/10.1016/j.annepidem.2025.01.004
- “Childhood Body Mass Index Trajectories, Adult-Onset Type 2 Diabetes and Obesity-Related Cancers.” J Natl Cancer Inst, Jan. 2023. https://pmc.ncbi.nlm.nih.gov/articles/PMC9830482/
- “Birthweight, Childhood Body Size, and Timing of Puberty and Risks of Breast Cancer by Menopausal Status and Tumor Receptor Subtypes.” Breast Cancer Research, Nov. 2022. https://pubmed.ncbi.nlm.nih.gov/36369105/
- “Early Life Body Size, Pubertal Timing, and Risks of Benign Breast Disease in a Large Cohort of Danish Female Adolescents and Women.” Eur J Pediatr, Aug. 2022. https://pubmed.ncbi.nlm.nih.gov/35652986/
