Table 2.
Hazard ratio (HR) with 95% confidence interval (CI) for obesity-related cancer risk by body mass index (BMI) category at enrolment
| Model 1 age-adjusted | Model 2 multivariable | |||||||
|---|---|---|---|---|---|---|---|---|
| N | Cancer cases | HR | 95% CI | N | Cancer cases | HR | 95% CI | |
| Overall obesity-related cancer a | ||||||||
| Underweight | 3022 | 173 | 0.95 | 0.82–1.10 | 2626 | 149 | 0.92 | 0.78–1.08 |
| Normal weight | 87,595 | 5689 | 1.00 | Reference | 77,064 | 4961 | 1.00 | Reference |
| Overweight | 34,656 | 2603 | 1.10 | 1.05–1.15 | 29,517 | 2154 | 1.09 | 1.03–1.14 |
| Obesity | 10,435 | 863 | 1.26 | 1.17–1.35 | 8706 | 699 | 1.24 | 1.14–1.34 |
| 5 BMI unit increment | 135,708 | 9328 | 1.11 | 1.08–1.14 | 117,913 | 7 963 | 1.10 | 1.07–1.13 |
| Postmenopausal breast cancer b | ||||||||
| Underweight | 899 | 27 | 0.96 | 0.66–1.41 | 650 | 19 | 0.98 | 0.62–1.55 |
| Normal weight | 32,831 | 1047 | 1.00 | Reference | 24,224 | 730 | 1.00 | Reference |
| Overweight | 19,270 | 638 | 1.04 | 0.95–1.15 | 14,079 | 448 | 1.13 | 1.00–1.27 |
| Obesity | 6331 | 206 | 1.07 | 0.92–1.24 | 4540 | 139 | 1.20 | 1.00–1.44 |
| 5 BMI unit increment | 59,331 | 1918 | 1.03 | 0.97–1.08 | 43,493 | 1 336 | 1.07 | 1.00–1.15 |
| Colorectal cancer c | ||||||||
| Underweight | 3022 | 39 | 1.11 | 0.80–1.52 | 2902 | 38 | 1.10 | 0.80–1.52 |
| Normal weight | 87,595 | 1 146 | 1.00 | Reference | 83,411 | 1083 | 1.00 | Reference |
| Overweight | 34,656 | 585 | 1.12 | 1.02–1.24 | 32,511 | 544 | 1.12 | 1.01–1.25 |
| Obesity | 10,435 | 157 | 1.05 | 0.88–1.24 | 9744 | 140 | 1.01 | 0.84–1.20 |
| 5 BMI unit increment | 135,708 | 1 927 | 1.05 | 0.99–1.11 | 128,568 | 1 805 | 1.04 | 0.98–1.11 |
| Colon cancer d | ||||||||
| Underweight | 3022 | 26 | 1.14 | 0.77–1.69 | 3017 | 26 | 1.13 | 0.76–1.67 |
| Normal weight | 87,595 | 746 | 1.00 | Reference | 87,355 | 743 | 1.00 | Reference |
| Overweight | 34,656 | 414 | 1.20 | 1.06–1.36 | 34,481 | 411 | 1.21 | 1.07–1.37 |
| Obesity | 10,435 | 104 | 1.05 | 0.85–1.29 | 10,378 | 103 | 1.06 | 0.86–1.30 |
| 5 BMI unit increment | 135,708 | 1 290 | 1.06 | 0.99–1.14 | 135,231 | 1 283 | 1.07 | 0.99–1.14 |
| Rectal cancer e | ||||||||
| Underweight | 3022 | 13 | 1.05 | 0.60–1.82 | 2805 | 11 | 0.99 | 0.54–1.81 |
| Normal weight | 87,595 | 400 | 1.00 | Reference | 79,948 | 354 | 1.00 | Reference |
| Overweight | 34,656 | 171 | 0.98 | 0.82–1.18 | 30,665 | 153 | 1.02 | 0.84–1.24 |
| Obesity | 10,435 | 53 | 1.05 | 0.78–1.40 | 9189 | 44 | 1.03 | 0.75–1.42 |
| 5 BMI unit increment | 135,708 | 637 | 1.03 | 0.93–1.14 | 122,607 | 562 | 1.04 | 0.93–1.16 |
| Endometrial cancer f | ||||||||
| Underweight | 2914 | 11 | 0.62 | 0.34–1.13 | 2594 | 10 | 0.63 | 0.34–1.18 |
| Normal weight | 83,620 | 539 | 1.00 | Reference | 74,239 | 489 | 1.00 | Reference |
| Overweight | 32,163 | 321 | 1.50 | 1.30–1.72 | 27,991 | 277 | 1.45 | 1.24–1.68 |
| Obesity | 9617 | 186 | 3.02 | 2.55–3.58 | 8326 | 156 | 2.78 | 2.30–3.35 |
| 5 BMI unit increment | 128,314 | 1057 | 1.53 | 1.45–1.62 | 113150 | 932 | 1.51 | 1.42–1.60 |
| Ovarian cancer g | ||||||||
| Underweight | 2991 | 11 | 0.75 | 0.41–1.36 | 2851 | 10 | 0.71 | 0.38–1.33 |
| Normal weight | 86,442 | 429 | 1.00 | Reference | 81,300 | 404 | 1.00 | Reference |
| Overweight | 33,816 | 149 | 0.91 | 0.75–1.10 | 31,608 | 142 | 0.92 | 0.76–1.12 |
| Obesity | 10,118 | 53 | 1.13 | 0.85–1.51 | 9425 | 49 | 1.09 | 0.81–1.48 |
| 5 BMI unit increment | 133,367 | 642 | 1.01 | 0.91–1.12 | 125,148 | 605 | 1.00 | 0.90–1.12 |
| Pancreatic cancer c | ||||||||
| Underweight | 3059 | 5 | 0.75 | 0.31–1.83 | 2902 | 4 | 0.55 | 0.20–1.48 |
| Normal weight | 88,480 | 213 | 1.00 | Reference | 83,411 | 202 | 1.00 | Reference |
| Overweight | 35,092 | 104 | 1.11 | 0.87–1.41 | 32,511 | 97 | 1.18 | 0.92–1.51 |
| Obesity | 10,574 | 28 | 1.05 | 0.70–1.56 | 9744 | 29 | 1.19 | 0.79–1.79 |
| 5 BMI unit increment | 135,708 | 350 | 1.02 | 0.89–1.17 | 128,568 | 324 | 1.11 | 0.96–1.27 |
| Kidney cancer h | ||||||||
| Underweight | 3059 | 2 | 0.40 | 0.10–1.60 | 2295 | 2 | 0.50 | 0.12–2.04 |
| Normal weight | 88,480 | 158 | 1.00 | Reference | 68,745 | 120 | 1.00 | Reference |
| Overweight | 35,092 | 94 | 1.41 | 1.08–1.82 | 26,124 | 62 | 1.32 | 0.96–1.81 |
| Obesity | 10,574 | 38 | 1.97 | 1.38–2.83 | 7502 | 27 | 1.95 | 1.26–3.02 |
| 5 BMI unit increment | 135,708 | 292 | 1.34 | 1.18–1.51 | 104,666 | 211 | 1.33 | 1.15–1.54 |
aModel 2 for overall obesity-related cancer was adjusted for age, education, physical activity and smoking status
bOnly in women who were postmenopausal at enrolment, model 2 for postmenopausal breast cancer was adjusted for age, education, alcohol intake, parity/age at first full-term pregnancy, oral contraceptive use, hormone therapy use and history of breast cancer in the mother
cModel 2 for colorectal and pancreatic cancer was adjusted for age, education and smoking status
dModel 2 for colon cancer was adjusted for age and smoking status
eModel 2 for rectal cancer was adjusted for age, education and alcohol intake
fModel 2 for endometrial cancer was adjusted for age, education, age at menarche, parity/age at first full-term pregnancy, oral contraceptive use and menopausal status
gModel 2 for ovarian cancer was adjusted for age, parity/age at first full-term pregnancy and oral contraceptive use
hModel 2 for kidney cancer was adjusted for age, smoking status and diabetes
The Norwegian Women and Cancer study, 1991–2014 (n = 135,708)