Breast cancer risk factors and their effects on survival: a Mendelian randomisation study

Table 1 Description of the nine risk factors with available genetic data from GWAS

Risk factor (units)	Number* of SNPs	GWAS Catalog accession number	Study reference	Sample size	Population
Alcohol consumption (drinks per week)^†	98	GCST007472	Liu et al. [24]	1,039,210	100% European
Body mass index (adult, kg/m²)	100	GCST006368	Hoffmann et al. [25]	334,487	81% European
Height (adult, m)	112	GCST002647	Wood et al. [26]	253,288	100% European
Mammographic density (dense vs non-dense area)	5	GCST002667	Lindström et al. [27]	16,015**	100% European
Menarche (age at onset)	82	GCST002541	Perry et al. [28]	182,413**	100% European
Menopause (age at onset)	34	GCST005312	Day et al. [29]	69,626**	100% European
Physical activity (overall physical activity time)	3	GCST006912	Doherty et al. [30]	91,105	100% European
Smoking behaviour (ever vs never)^‡	119	GCST007327	Karlsson Linnér et al. [31]	518,633	100% European
Type 2 diabetes mellitus (yes vs no)	95	GCST006867	Xue et al. [32]	659,316 (62,892 cases and 596,424 controls)	99% European

*The number of SNPs here may be lower than in the GWAS due to filtering (see the “Methods” section)
**Partial overlap with samples from BCAC
^†Defined as the average number of drinks a participant reported drinking each week, aggregated across all types of alcohol
^‡This is a binary phenotype. Participants who reported ever being a regular smoker in their life (current or former) were coded “2”, while participants who reported never being a regular smoker in their life were coded “1”

ISSN: 1741-7015