Table 2.
Type 2 Diabetes and Breast Cancer Risk, Reykjavik and AGES Study, 1968–2015
| Characteristic | Exposure category | Number of cases | Person-years | HRa | 95% CI | |||
|---|---|---|---|---|---|---|---|---|
| Exposed | Unexposed | Exposed | Unexposed | |||||
| Reykjavik Study | T2D (model without BMI) | 16 | 712 | 6,023 | 266,738 | 0.99 | 0.60, 1.64 | |
| (N=9,606) | T2D (model with BMI) | 16 | 712 | 6,023 | 266,738 | 0.95 | 0.57, 1.56 | |
| T2D (postmenopausal) | 16 | 690 | 6,023 | 266,480 | 0.95 | 0.58, 1.57 | ||
| IFGb | 8 | 720 | 3,165 | 269,596 | 0.88 | 0.44, 1.78 | ||
| T2D and IFGc | 26 | 702 | 9,606 | 269,596 | 0.95 | 0.64, 1.42 | ||
| Fasting glucose (per 10 mg/dL) | 16 | 712 | 6,023 | 266,738 | 1.02 | 0.96, 1.08 | ||
| AGES Studyd | T2D (model without BMI) | 11 | 82 | 2,912 | 27,857 | 1.24 | 0.66, 2.36 | |
| (N=3,103) | T2D (model with BMI) | 11 | 82 | 2,912 | 27,857 | 1.18 | 0.62, 2.27 | |
| IFG | 35 | 58 | 10,243 | 20,526 | 1.19 | 0.78, 1.82 | ||
| T2D and IFG | 46 | 47 | 13,155 | 17,614 | 1.26 | 0.83, 1.92 | ||
| Fasting glucose (per 10 mg/dL) | 11 | 82 | 2,912 | 27,857 | 0.97 | 0.87, 1.09 | ||
| Stratified Models for Reykjavik Study | ||||||||
| Hormone receptorsd | ER+/PR+ | 4 | 264 | 5,915 | 259,410 | 0.69 | 0.25, 1.87 | |
| ER-/PR- | 3 | 95 | 5,894 | 254,971 | 1.22 | 0.38, 3.93 | ||
| ER+/PR- and ER-/PR+ | 1 | 133 | 5,877 | 255,751 | 0.28 | 0.04, 2.03 | ||
| Tumor stagee | TNM 1 | 9 | 363 | 5,966 | 259,869 | 1.05 | 0.54, 2.05 | |
| TNM 2 | 2 | 258 | 5,880 | 258,439 | 0.31 | 0.08, 1.24 | ||
| TNM 3/4 | 4 | 43 | 5,893 | 253,918 | 3.30 | 1.13, 9.62 | ||
Hazard ratios (HR) and 95% confidence intervals (CI) obtained by Cox regression with age as time metric and adjusted for BMI (except when noted), height, birth cohort, education, place of residence, smoking status, physical activity, age at menarche, parity, and age at first live birth
Presence of impaired fasting glucose (100–125 mg/dL)
Presence of impaired fasting glucose (100–125 mg/dL) or T2D based on self-report of fasting glucose
Women in AGES study (N=3,103); models also include alcohol intake, hormone treatment, and breast feeding. Parity and age at first live birth were combined into one variable (no children, parous <25 or ≥25 years).
Values were missing on hormone receptors for 228 cases and on tumor stage for 49 cases
Abbreviations: ER=estrogen receptor; PR=progesterone receptor; TNM=tumor, nodes, metastasis classification; BMI=body mass index.