Background: Mammographic breast density has been suggested to play a role as a mediator between the risk factors for breast cancer (BC) and BC risk. We investigated the extent to which never breastfeeding is a risk factor for BC and how this risk is further mediated by increased mammographic breast density.
Methods: This retrospective cohort study included 4 136 723 women aged ≥40 years who underwent mammographic screening between 2009 and 2010 and were followed up until 31 December 2020. Breastfeeding information was obtained by using a self-administered questionnaire. Mammographic breast density was extracted from national BC screening results, which were assessed by trained radiologists and categorized into dense and fatty breasts. We estimated the hazard ratios (HRs) and the proportion of the associations between breastfeeding and BC risk mediated by breast density.
Results: The HR of never breastfeeding on BC risk was 1.34 (95% CI, 1.32-1.37) when adjusted for only parity, body mass index and smoking status, which were selected as covariates through a directed acyclic graph and 1.21 (95% CI, 1.19-1.23) when breast density was additionally adjusted. The proportion of the association between never breastfeeding and BC risk mediated by breast density in total, pre- and post-menopausal women was 35.48%, 17.86% and 24.0%, respectively (all P < 0.001). The HR of never breastfeeding on BC risk was 1.10 (95% CI, 1.08-1.12) when adjusted for nine known breast cancer risk factors and 1.09 (95% CI, 1.07-1.12) when breast density was additionally adjusted. The proportion of the association between never breastfeeding and BC risk mediated by breast density in the total, pre- and post-menopausal women was 7.50%, 3.71% and 12.21%, respectively (all P < 0.001).
Conclusions: Our findings suggest that the association between never breastfeeding and BC risk may be mediated by breast density. However, the HR and proportion of medications varied according to the adjusted covariates, highlighting that variables for adjustment should be selected based on directed acyclic graphs.
Background: Adiposity is an established risk factor for colorectal cancer (CRC). The pathways underlying this relationship, and specifically the role of circulating proteins, are unclear.
Methods: Utilizing two-sample univariable Mendelian randomization (UVMR), multivariable Mendelian randomization (MVMR), and colocalization, based on summary data from large sex-combined and sex-specific genetic studies, we estimated the univariable associations between: (i) body mass index (BMI) and waist-hip ratio (WHR) and overall and site-specific (colon, proximal colon, distal colon, and rectal) CRC risk, (ii) BMI and WHR and circulating proteins, and (iii) adiposity-associated circulating proteins and CRC risk. We used MVMR to investigate the potential mediating role of adiposity- and CRC-related circulating proteins in the adiposity-CRC association.
Results: BMI and WHR were positively associated with CRC risk, with similar associations by anatomical tumor site. In total, 6591 adiposity-protein (2628 unique circulating proteins) and 33 protein-CRC (7 unique circulating proteins) associations were identified using UVMR and colocalization. One circulating protein, GREM1, was associated with BMI (only) and CRC outcomes in a manner that was consistent with a potential mediating role in sex-combined and female-specific analyses. In MVMR, adjusting the BMI-CRC association for GREM1, effect estimates were attenuated-suggestive of a potential mediating role-most strongly for the BMI-overall CRC association in women.
Conclusion: Results highlight the impact of adiposity on the plasma proteome and of adiposity-associated circulating proteins on the risk of CRC. Supported by evidence from UVMR and colocalization analyses using cis-single-nucleotide polymorphisms, GREM1 was identified as a potential mediator of the BMI-CRC association, particularly in women.
Background: Although autoimmune abnormalities are common in patients with endometriosis, it is unknown whether patients with endometriosis have a higher risk of developing antiphospholipid syndrome (APS).
Methods: We conducted a retrospective cohort study by using the multi-institutional research network TriNetX from 1 January 2012 to 31 December 2021. A total of 13 131 782 women aged 20-60 years from networks within the USA were included. The risks of APS were compared between an endometriosis cohort and a non-endometriosis cohort in subgroup analyses by age, obesity and systemic lupus erythematosus (SLE), and the sensitivity analysis was stratified by the presence or absence of a history of surgery of the uterus.
Results: After 1:1 propensity score matching, the endometriosis and non-endometriosis cohorts each included 50 078 participants. Compared to individuals without endometriosis, patients with endometriosis had a higher risk of incident APS (log-rank test, P < 0.001). The hazard ratios (HRs) ranged from 1.82 [APS within 30 days to 1 year after the index date, 95% confidence intervals (CIs) 1.40-2.53] to 2.44 (APS within 30 days to any time after the index date, 95% CI 1.65-3.61). In the subgroup analyses, an increased risk of APS was observed in all ages, White race, and subgroups without smoking, obesity, asthma, inflammatory bowel disease and SLE (HR range 1.85-2.84). Sensitivity analyses revealed that the risk of APS increased in patients without surgery history of the uterus.
Conclusions: Patients with endometriosis had a higher risk (2.84-fold) of developing APS. Future large-scale prospective studies are warranted to confirm our results.