Table 1. Comparison of the UK Population Exposed and Not Exposed to Incident ON.
| Characteristic at baseline | ON, No. (%) | Single-variable IRR (95% CI) | P value | aIRR (95% CI) | P value | |
|---|---|---|---|---|---|---|
| Yes (n = 2826) | No (n = 10 934 685) | |||||
| Female sex | 1962 (69.4) | 5 569 320 (50.9) | 2.26 (2.09-2.45) | <.001 | 2.26 (2.08-2.45) | <.001 |
| Age group at cohort entry, y | ||||||
| 1-10 | 121 (4.3) | 2 070 338 (19.9) | 1 [Reference] | NA | 1 [Reference] | NA |
| 11-20 | 284 (10.1) | 1 081 405 (9.9) | 4.56 (3.69-5.64) | <.001 | 4.53 (3.65-5.62) | <.001 |
| 21-30 | 704 (24.9) | 1 984 337 (18.2) | 7.81 (6.44-9.47) | <.001 | 6.80 (5.50-8.40) | <.001 |
| 31-40 | 796 (28.2) | 1 814 484 (16.6) | 6.98 (5.77-8.45) | <.001 | 6.04 (4.89-7.46) | <.001 |
| 41-50 | 473 (16.7) | 1 324 681 (12.1) | 4.84 (3.97-5.91) | <.001 | 4.15 (3.33-5.16) | <.001 |
| 51-60 | 235 (8.3) | 1 045 254 (9.6) | 2.92 (2.35-3.64) | <.001 | 2.45 (1.93-3.10) | <.001 |
| 61-70 | 125 (4.4) | 765 334 (7.0) | 2.21 (1.72-2.83) | <.001 | 1.82 (1.39-2.38) | <.001 |
| 71-80 | 67 (2.4) | 526 666 (4.8) | 2.08 (1.55-2.81) | <.001 | 1.69 (1.24-2.31) | <.001 |
| 81-90 | 21 (0.7) | 270 755 (2.5) | 2.11 (1.33-3.36) | .002 | 1.68 (1.05-2.69) | <.001 |
| 91-100 | 0 | 50 687 (0.5) | NA | NA | NA | NA |
| ≥101 | 0 | 744 (0.0) | NA | NA | NA | NA |
| Nation | ||||||
| England | 1943 (68.8) | 7 790 740 (71.3) | 1 [Reference] | NA | 1 [Reference] | NA |
| Scotland | 452 (16.0) | 1 538 041 (14.1) | 1.22 (1.10-1.35) | <.001 | 1.19 (1.08-1.32) | .001 |
| Wales | 285 (10.1) | 1 203 405 (11.0) | 0.91 (0.81-1.04) | .16 | 0.91 (0.80-1.03) | .15 |
| Northern Ireland | 146 (5.2) | 402 499 (3.4) | 1.07 (0.90-1.26) | .44 | 1.08 (0.91-1.28) | .38 |
| Townsend Deprivation Index quintile | ||||||
| 1 (Least deprived) | 599 (21.2) | 1 984 597 (18.2) | 1 [Reference] | NA | NI | NI |
| 2 | 511 (18.1) | 1 807 282 (16.5) | 0.99 (0.88-1.11) | .84 | ||
| 3 | 513 (18.2) | 1 910 584 (17.5) | 1.01 (0.90-1.14) | .87 | ||
| 4 | 434 (15.4) | 1 783 263 (16.3) | 0.98 (0.87-1.11) | .76 | ||
| 5 (Most deprived) | 302 (10.7) | 1 314 297 (12.0) | 0.95 (0.83-1.10) | .51 | ||
| Missing | 467 (16.5) | 2 134 662 (19.5) | 1.03 (0.91-1.16) | .65 | ||
| Race/ethnicity | ||||||
| White | 1192 (42.2) | 4 262 489 (39.0) | 1 [Reference] | NA | 1 [Reference] | NA |
| Black | 42 (1.5) | 177 881 (1.6) | 1.21 (0.89-1.65) | .22 | 1.16 (0.85-1.58) | .34 |
| Mixed | 12 (0.4) | 131 325 (1.2) | 0.58 (0.33-1.03) | .06 | 0.52 (0.30-0.92) | .02 |
| Other | 13 (0.5) | 70 383 (0.6) | 1.05 (0.61-1.81) | .86 | 1.14 (0.66-1.97) | .64 |
| South Asian | 31 (1.1) | 262 376 (2.4) | 0.55 (0.39-0.79) | .001 | 0.56 (0.39-0.80) | .001 |
| Missing | 1536 (54.4) | 6 030 231 (55.2) | 0.87 (0.81-0.94) | <.001 | 0.97 (0.89-1.05) | .40 |
| BMI at cohort entry | ||||||
| Underweight (<18.5) | 46 (1.6) | 182 124 (1.7) | 0.96 (0.71-1.29) | .77 | 0.83 (0.61-1.11) | .21 |
| Normal (18.5-24.9) | 906 (32.1) | 2 795 714 (25.6) | 1 [Reference] | NA | 1 [Reference] | NA |
| Overweight (25.0-29.9) | 549 (19.4) | 1 918 201 (17.5) | 0.81 (0.73-0.91) | <.001 | 1.04 (0.94-1.16) | .44 |
| Obese (30.0-34.9) | 259 (9.2) | 733 314 (6.7) | 1.03 (0.90-1.19) | .64 | 1.27 (1.11-1.46) | .001 |
| Morbidly obese (>35.0) | 151 (5.3) | 355 770 (3.2) | 1.30 (1.10-1.55) | .003 | 1.37 (1.15-1.63) | <.001 |
| Missing BMI | 915 (32.4) | 4 949 562 (45.3) | 0.54 (0.49-0.59) | <.001 | 0.92 (0.82-1.04) | .18 |
| Smoking status at cohort entry | ||||||
| Never smoker | 1165 (41.2) | 4 229 870 (38.7) | 1 [Reference] | NA | 1 [Reference] | NA |
| Ex-smoker | 312 (11.0) | 1 158 945 (10.6) | 1.03 (0.91-1.17) | .66 | 1.19 (1.05-1.35) | .007 |
| Current smoker | 701 (24.8) | 1 852 089 (16.9) | 1.37 (1.25-1.50) | <.001 | 1.32 (1.20-1.45) | <.001 |
| Missing | 648 (22.9) | 3 693 781 (33.8) | 0.56 (0.51-0.62) | <.001 | 1.09 (0.95-1.24) | .22 |
Abbreviations: aIRR, adjusted incident rate ratio; BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); NA, not applicable; NI, not included in model; ON, optic neuritis.