Table 1.
Description of genetic instruments for observed environmental risk factors.
| Potential risk factor | n SNP | Mean | SD | Units | Var (%) | Pub ref | Minimum detectable OR | ||
|---|---|---|---|---|---|---|---|---|---|
| IBD | CD | UC | |||||||
| Lifestyle | |||||||||
| Smoking status | 331 | - | - | Ever/never | 2.3 | 12 | 1.17 | 1.22 | 1.21 |
| Cigarettes per day | 44 | 2.35 | 0.94 | n cigarettes | 1.1 | 12 | 1.25 | 1.34 | 1.32 |
| Body-mass index | 816 | 26.97 | 4.65 | Kg/m2 | 6.0 | 13 | 1.10 | 1.13 | 1.13 |
| Waist-to-hip ratio | 403 | 1 | 0.1 | – | 3.0 | 14 | 1.14 | 1.19 | 1.19 |
| Body fat percentage (fat/total mass) | 378 | 31.8 | 6.6 | % | 3.5 | 15 | 1.13 | 1.18 | 1.17 |
| Overall physical activity | 2 | 27.89 | 8.14 | Mili-gravities (acceleration) | 0.08 | 16 | 2.27 | 2.93 | 2.83 |
| Nutrients | |||||||||
| Vitamin D | 59 | 70.0 | 34.7 | nmol/l | 3.4 | 19 | 1.13 | 1.18 | 1.17 |
| Vitamin B9 (folate) | 2 | 13.4 | 8.44 | nmol/l | 1.0 | 20 | 1.26 | 1.36 | 1.34 |
| Vitamin B12 | 10 | 342.68 | 150.11 | pmol/L | 6.3 | 20 | 1.10 | 1.13 | 1.12 |
| Omega-3 fatty acids | 4 | 0.41 | 0.08–1.80* | mmol/l | 2.4 | 21 | 1.16 | 1.22 | 1.21 |
| Omega-6 fatty acids | 8 | 4 | 1.8–12.0* | mmol/l | 4.6 | 21 | 1.11 | 1.15 | 1.15 |
| Monounsaturated fatty acids (mainly omega-9 and omega-7) | 4 | 3.3 | 1.1–15.0* | mmol/l | 2.4 | 21 | 1.16 | 1.22 | 1.21 |
| Total fatty acids | 8 | 11.7 | 4.6–42.0* | mmol/l | 3.7 | 21 | 1.13 | 1.17 | 1.17 |
nSNP number of single nucleotide polymorphisms, SD standard deviation, Var: explained phenotype variance, Pub ref discovery GWAS, OR odds ratio; IBD Inflammatory bowel disease; CD Crohn’s disease; UC ulcerative colitis.
*Range (minimum–maximum).