Table 5.

Multivariable-adjusted hazard ratio of breast cancer by early adulthood energy-adjusted glycemic index, glycemic load, insulin index, and insulin load stratified by BMI at age 18 among women in the Nurses’ Health Study II

		Quintile of intake						P-value, test for interaction
	Cases/Person-year	1	2	3	4	5	P-value, test for trend
Adolescence
Glycemic index
<25 kg/m2	1064/540,912	1	1.18 (0.99–1.42)	0.86 (0.70–1.04)	0.97 (0.80–1.18)	1.13 (0.93–1.36)	0.78	0.99
≥25 kg/m2	63/57,568	1	1.62 (0.63–4.19)	1.88 (0.72–4.87)	1.83 (0.72–4.61)	2.36 (0.97–5.78)	0.06
Glycemic load
<25 kg/m2	1064/540,912	1	1.16 (0.96–1.39)	1.00 (0.82–1.22)	1.03 (0.85–1.25)	1.04 (0.85–1.27)	0.94	0.31
≥25 kg/m2	63/57,568	1	1.27 (0.60–2.69)	1.05 (0.42–2.58)	0.76 (0.32–1.82)	1.06 (0.44–2.55)	0.75
Insulin index
<25 kg/m2	1064/540,912	1	0.92 (0.77–1.11)	0.95 (0.78–1.14)	0.94 (0.78–1.14)	0.89 (0.73–1.09)	0.33	0.34
≥25 kg/m2	63/57,568	1	1.85 (0.86–3.96)	0.72 (0.28–1.85)	1.26 (0.53–2.95)	1.09 (0.43–2.79)	0.84
Insulin load
<25 kg/m2	1064/540,912	1	0.90 (0.74–1.08)	0.90 (0.74–1.08)	0.94 (0.78–1.14)	0.88 (0.72–1.07)	0.31	0.34
≥25 kg/m2	63/57,568	1	2.18 (0.97–4.86)	1.13 (0.47–2.69)	1.03 (0.42–2.57)	1.37 (0.54–3.44)	0.99
Early adulthood
Glycemic index
<25 kg/m2	2672/1,562,327	1	1.00 (0.88–1.12)	1.05 (0.93–1.18)	1.03 (0.91–1.16)	1.02 (0.90–1.16)	0.61	0.55
≥25 kg/m2	190/178,868	1	1.10 (0.70–1.71)	1.56 (1.01–2.41)	1.00 (0.61–1.62)	1.09 (0.67–1.79)	0.66
Glycemic load
<25 kg/m2	2672/1,562,327	1	0.92 (0.81–1.03)	0.89 (0.79–1.00)	0.90 (0.79–1.02)	0.94 (0.83–1.07)	0.37	0.04
≥25 kg/m2	190/178,868	1	1.24 (0.81–1.92)	1.43 (0.92–2.22)	1.39 (0.87–2.22)	1.19 (0.70–2.02)	0.30
Insulin index
<25 kg/m2	2672/1,562,327	1	0.89 (0.79–1.01)	1.01 (0.90–1.14)	0.94 (0.83–1.06)	0.90 (0.80–1.03)	0.23	0.55
≥25 kg/m2	190/178,868	1	0.68 (0.43–1.07)	0.63 (0.39–1.03)	1.08 (0.69–1.68)	1.06 (0.67–1.69)	0.47
Insulin load
<25 kg/m2	2672/1,562,327	1	0.93 (0.82–1.05)	0.98 (0.87–1.11)	0.97 (0.85–1.09)	0.92 (0.81–1.04)	0.34	0.71
≥25 kg/m2	190/178,868	1	0.91 (0.58–1.41)	0.82 (0.51–1.31)	0.98 (0.61–1.57)	1.24 (0.77–1.99)	0.40

Multivariable model was stratified by age in months at start of follow-up and calendar year of the current questionnaire cycle and was simultaneously adjusted for race (white, non-white), family history of breast cancer in mother or sisters (yes, no), history of benign breast disease (yes, no), smoking (never, past, current 1 to 14/day, current 15 to 24/day, current ≥25/day), height (<62, 62 to <65, 65 to <68, ≥68 inches), weight gain since age 18 (≤−5, >−5–5, >5–10, >10–20, >20 kg), age at menarche (<12, 12, 13, ≥14 years), parity and age at first birth (nulliparous, parity ≤2 and age at first birth <25 years, parity≤2 and age at first birth 25 to <30 years, parity ≤2 and age at first birth ≥30 years, parity 3 to 4 and age at first birth <25 years, parity 3 to 4 and age at first birth 25 to <30 years, parity 3 to 4 and age at first birth ≥30 years, parity ≥5 and age at first birth <25 years, parity ≥5 and age at first birth ≥25 years), oral contraceptive use (never, past, current), alcohol intake (nondrinker, <5, 5 to <15, ≥15 g/day), and energy (quintile). In postmenopausal women, we additionally adjusted for hormone use (postmenopausal never users, postmenopausal past users, postmenopausal current users), age at menopause (<45 years, 45 to 46 years, 47 to 48, 49 to 50 years, 51 to 52 years, ≥53 years). Among all women, we additionally adjusted for hormone use and menopausal status (premenopausal, postmenopausal never users, postmenopausal past users, postmenopausal current users, unknown menopausal status) and, age at menopause (premenopausal, unknown menopause, <45 years, 45 to 46 years, 47 to 48, 49 to 50 years, 51 to 52 years, ≥53 years). For adolescent GI, we additionally adjusted for adolescent alcohol intake (nondrinker, <1.5, 1.5–<5, 5–<10, ≥10 g/day) and adolescent energy intake (instead of adult energy intake).