Table 1.

Characteristics of study participants in each cohort according to caffeine intake at baseline^*

	Caffeine intake (mg/day)
	Nurses’ Health Study				Nurses’ Health Study II
	0–149	150–299	300–449	≥ 450	0–149	150–299	300–449	≥ 450
Characteristic†	(n=16211)	(n=4524)	(n=9245)	(n=2681)	(n=14180)	(n=5108)	(n=7712)	(n=2654)
Mean age, years (SD)	65.9 (7.0)	65.0 (7.0)	65.1 (6.9)	64.2 (6.6)	45.8 (4.8)	45.9 (4.7)	46.4 (4.6)	46.5 (4.4)
Mean BMI, kg/m2 (SD)	25.9 (4.8)	26.0 (4.7)	25.6 (4.5)	25.6 (4.7)	25.5 (5.6)	25.7 (5.5)	25.2 (4.9)	25.6 (5.2)
Mean physical activity, metabolic equivalent-hrs/wk (SD)	19.3 (17.3)	18.6 (16.9)	19.3 (16.9)	18.8 (17.0)	22.7 (22.0)	22.5 (21.4)	23.3 (22.3)	22.1 (21.4)
Mean fluid intake, L/day (SD)	2.0 (0.7)	2.0 (0.8)	2.1 (0.7)	2.3 (0.8)	1.7 (0.6)	2.0 (0.6)	2.1 (0.6)	2.5 (0.6)
Race (%)
White	94.9	95.2	96.7	96.9	95.0	95.8	97.1	98.0
Black	1.7	1.5	0.6	0.6	1.6	1.1	0.5	0.2
Asian	0.9	0.7	0.4	0.3	1.5	1.3	0.7	0.5
Other/missing	2.5	2.6	2.3	2.2	1.9	1.8	1.7	1.4
Parity (%)
0	6.3	5.7	6.0	6.3	21.8	21.3	21.8	23.5
1–2	37.5	35.5	34.8	34.9	51.6	51.6	52.1	49.4
≥ 3	56.2	58.9	59.2	58.8	26.7	27.2	26.1	27.1
Cigarette smoking (%)
Never	51.3	48.2	37.5	30.4	77.5	68.6	56.4	46.6
Past	43.7	44.7	50.3	44.7	18.5	24.7	33.7	31.8
Current, cigarettes/day (%)
1–14	3.0	4.1	6.5	10.7	2.5	4.2	6.2	10.4
15–24	1.6	2.2	4.6	10.9	1.1	1.9	3.1	8.3
25–34	0.3	0.7	0.7	2.6	0.2	0.4	0.5	2.2
≥ 35	0.1	0.2	0.4	0.8	0.1	0.2	0.2	0.7
Diabetes (%)	7.1	7.4	5.3	4.6	2.1	2.4	1.4	2.1

^*Women who became eligible for analysis after baseline are not included in the table (n=2,861).

^†Percentages may not sum to 100% due to rounding.