Table 1.

Baseline characteristics of the analytic cohort

	Premenopausal				Postmenopausal, current HT use				Postmenopausal, not using HT
	(N = 46,822)				(N = 36,977)				(N = 21,788)
	Number	%	Median	IQR	Number	%	Median	IQR	Number	%	Median	IQR
Age (years)			41	34–46			57	52–65			64	55–72
Age at menarche (years)			12	12–13			12	12–13			13	12–13
Parous	30,580	65.3%			28,793	77.9%			16,440	75.5%
Age at first full-term pregnancy (among parous)			28	25–30			25	22–28			25	23–29
History of benign breast biopsy	4491	9.6%			7726	20.9%			3776	17.3%
Mother or sister with breast cancer	4482	9.6%			4503	12.2%			3241	14.9%
Consumption of a plant-based diet (factor score)			-0.35	-0.86 -0.33			-0.07	-0.65 -0.65			0.01	-0.60 -0.76
Alcohol consumption (g/day)
none	15,215	32.5%			10,463	28.3%			7810	35.8%
<20	26,397	56.4%			21,315	57.6%			10,803	49.6%
≥20	2692	5.7%			3575	9.7%			1918	8.8%
Socioeconomic status (deciles)
1–2 (low)	1820	3.9%			1053	2.8%			968	4.4%
3–4	5858	12.5%			3676	9.9%			2833	13.0%
5–6	8656	18.5%			5552	15.0%			3683	16.9%
7–8	14,884	31.8%			10,673	28.9%			6224	28.6%
9–10 (high)	15,041	32.1%			15,559	42.1%			7777	35.7%

Percent of missing data: age 0%; age at menarche 1%; parous 2%; age at first full-term pregnancy (n = 2); history of benign breast biopsy 0.4%; mother or sister with breast cancer 3% (includes women who were adopted); dietary factor score 9%; alcohol consumption 5%; and socioeconomic status 1%. HT hormone therapy