Characteristics of prevalent disease cohorts at the time of diagnosis and matched controls at the matched index date
| Characteristic | Disease and cohort; no (%) of patients* | |||||||
|---|---|---|---|---|---|---|---|---|
| Inflammatory bowel disease | Multiple sclerosis | Rheumatoid arthritis | IMID† | |||||
| Controls n = 50 704 | Cases† n = 10 148 | Controls n = 30 690 | Cases† n = 6158 | Controls n = 84 756 | Cases† n = 16 975 | Controls n = 164 152 | Cases† n = 32 880 | |
| Whole population, 1984–2015 | ||||||||
| Sex, female | 27 663 (54.6) | 5536 (54.6) | 21 564 (70.3) | 4322 (70.2) | 61 231 (72.2) | 12 263 (72.2) | 109 065 (66.4) | 21 841 (66.4) |
| Age at diagnosis, yr, mean ± SD (range) | 41.7 ± 17.0 (18 to 99) | 41.7 ± 17.0 (18 to 99) | 42.1 ± 13.5 (18 to 97) | 42.1 ± 13.5 (18 to 96) | 54.0 ± 16.1 (18 to 105) | 54.0 ± 16.1 (18 to 103) | 48.0 ± 17.1 (18 to 105) | 48.0 ± 17.1 (18 to 103) |
| Duration of follow-up from index date, yr, median (IQR) | 11.9 (4.92 to 21.8) | 13.3 (5.93 to 22.8) | 13.9 (5.91 to 23.6) | 13.9 (6.28 to 22.5) | 11.1 (4.93 to 19.3) | 11.4 (5.51 to 19.0) | 11.9 (5.12 to 20.8) | 12.4 (5.79 to 20.7) |
| Urban region of residence | 33 799 (66.7) | 6763 (66.6) | 20 685 (67.4) | 4154 (67.5) | 50 281 (59.3) | 10 070 (59.3) | 103 468 (63.0) | 20 727 (63.0) |
| Socioeconomic status,‡§ mean ± SD | −0.23 ± 0.88 | −0.26 ± 0.91 | −0.22 ± 0.88 | −0.25 ± 0.91 | 0.06 ± 1.01 | 0.03 ± 1.03 | −0.08 ± 0.96 | −0.11 ± 0.99 |
| Physician visits in prior year | ||||||||
| 0–4 | 41 688 (82.2) | 6569 (64.7) | 24 637 (80.3) | 3860 (62.7) | 63 997 (75.5) | 8416 (45.6) | 128 760 (78.4) | 19 997 (60.8) |
| 5–9 | 6517 (12.9) | 2172 (21.4) | 4196 (13.7) | 1313 (21.3) | 14 230 (16.8) | 3718 (21.9) | 24 623 (15.0) | 7297 (22.2) |
| ≥ 10 | 2499 (4.9) | 1407 (13.9) | 1857 (6.0) | 985 (16.0) | 6529 (7.7) | 4841 (28.5) | 10 769 (6.6) | 5586 (17.0) |
| Comorbidity status at study start | ||||||||
| No. of ADGs | ||||||||
| 0 | 42 318 (83.5) | 6749 (66.5) | 26 373 (85.9) | 4389 (71.3) | 65 883 (77.7) | 11 216 (66.1) | 133 038 (81.0) | 22 275 (67.7) |
| 1 | 7246 (14.3) | 2789 (27.5) | 3763 (12.3) | 1392 (22.6) | 15 605 (18.4) | 4643 (27.4) | 26 227 (16.0) | 8561 (26.0) |
| ≥ 2 | 1140 (2.2) | 610 (6.0) | 554 (1.8) | 377 (6.1) | 3268 (3.9) | 1116 (6.6) | 4887 (3.0) | 2044 (6.2) |
| Any mood or anxiety disorder | 10 979 (21.7) | 3147 (31.0) | 7431 (24.2) | 2485 (40.4) | 22 078 (26.0) | 5735 (33.8) | 39 911 (24.3) | 11 171 (34.0) |
| Depression | 9590 (18.9) | 2764 (27.2) | 6546 (21.3) | 2197 (35.7) | 18 853 (22.2) | 4864 (28.7) | 34 480 (21.0) | 9645 (29.3) |
| Anxiety disorder | 13 438 (26.5) | 3453 (34.0) | 8931 (29.1) | 2378 (38.6) | 25 922 (30.6) | 6074 (35.8) | 47 639 (29.0) | 11 707 (35.6) |
| Bipolar disorder | 1562 (3.1) | 548 (5.4) | 1151 (3.8) | 368 (6.0) | 2963 (3.5) | 716 (4.2) | 5583 (3.4) | 1602 (4.9) |
| Population, 2006–2015 | n = 40 364 | n = 8458 | n = 24 154 | n = 4748 | n = 64 510 | n = 12 984 | n = 127 310 | n = 25 832 |
| Sex, female | 22 207 (55.0) | 4623 (54.7) | 17 247 (71.4) | 3399 (71.6) | 47 102 (73.0) | 9458 (72.8) | 85 349 (67.0) | 8602 (33.3) |
| Age at diagnosis, yr, mean ± SD (range) | 41.2 ± 16.2 (18 to 99) | 41.0 ± 16.2 (18 to 99) | 40.9 ± 12.2 (18 to 97) | 40.2 ± 11.9 (18 to 94) | 51.8 ± 15.2 (18 to 105) | 51.4 ± 15.4 (18 to 102) | 46.4 ± 16.0 (18 to 105) | 45.9 ± 16.0 (18 to 102) |
| Urban region of residence | 26 558 (65.8) | 5574 (65.9) | 15 925 (65.9) | 3153 (66.4) | 37 559 (58.2) | 7609 (58.6) | 78 949 (62.0) | 16 104 (62.3) |
| Socioeconomic status,‡ mean ± SD | −0.22 ± 0.85 | −0.26 ± 0.89 | −0.21 ± 0.85 | −0.25 ± 0.89 | 0.06 ± 1.0 | 0.04 ± 1.0 | −0.08 ± 0.95 | −0.11 ± 0.98 |
| Physician visits in prior year | ||||||||
| 0–4 | 26 789 (66.4) | 3810 (45.0) | 15 224 (63.0) | 2260 (47.6) | 37 960 (58.8) | 4745 (36.5) | 78 891 (62.0) | 10 716 (41.5) |
| 5–9 | 8700 (21.6) | 2358 (27.9) | 5711 (23.6) | 1313 (27.7) | 16 064 (24.9) | 3593 (27.7) | 30 072 (23.6) | 7171 (27.8) |
| ≥ 10 | 4875 (12.1) | 2290 (27.1) | 3219 (13.3) | 1175 (24.7) | 10 486 (16.3) | 4646 (35.8) | 18 347 (14.4) | 7945 (30.8) |
| Comorbidity status at index date | ||||||||
| No. of ADGs | ||||||||
| 0 | 33 895 (84.0) | 5546 (65.6) | 20 903 (86.5) | 3371 (71.0) | 51 284 (79.5) | 8594 (66.2) | 104 753 (82.3) | 17 434 (67.5) |
| 1 | 5638 (14.0) | 2390 (28.2) | 2892 (12.0) | 1089 (22.9) | 11 140 (17.3) | 3577 (27.5) | 19 340 (15.2) | 6827 (26.4) |
| ≥ 2 | 831 (2.0) | 522 (6.2) | 359 (1.5) | 288 (6.1) | 2086 (3.2) | 813 (6.3) | 3217 (2.5) | 1571 (6.1) |
| Any mood and anxiety disorder | 9108 (22.6) | 2669 (31.6) | 6119 (25.3) | 1985 (41.8) | 17 008 (26.4) | 4490 (34.6) | 31 739 (24.9) | 8960 (34.7) |
| Depression | 7992 (19.8) | 2343 (27.7) | 5410 (22.4) | 1742 (36.7) | 14 548 (22.6) | 3808 (29.3) | 27 517 (21.6) | 7723 (29.9) |
| Anxiety disorder | 11 444 (28.4) | 2980 (35.2) | 7543 (31.2) | 1983 (41.8) | 21 332 (33.1) | 5063 (39.0) | 39 735 (31.2) | 9839 (38.1) |
| Bipolar disorder | 1326 (3.3) | 465 (5.5) | 968 (4.0) | 301 (6.3) | 2347 (3.6) | 575 (4.4) | 4559 (3.6) | 1312 (5.1) |
Note: IMID = immune-mediated inflammatory disease (IMID cohort combines patients with inflammatory bowel disease, multiple sclerosis and rheumatoid arthritis).
↵* Except where indicated otherwise.
↵† A small number of individuals met the case definitions for more than 1 of the IMIDs of interest. These were included in the analysis, to ensure generalizability of the findings, but they were counted only once in the combined IMID cohort. In this situation, they were classified on the basis of the IMID with the earliest index date in the coverage period. Some cases did not have 5 matched controls (IMID, n = 90; inflammatory bowel disease, n = 14; multiple sclerosis, n = 36; rheumatoid arthritis, n = 42).
↵‡ Socioeconomic status is reported as the Socioeconomic Factor Index score, incorporating information about average household income, percent of single-parent households, unemployment rate and high school education rate, with missing values imputed at the mean of 0. With this measure, values less than 0 indicate higher socioeconomic status.
↵§ Missing data: for multiple sclerosis, 20; for multiple sclerosis controls, 110; for inflammatory bowel disease, 21; for inflammatory bowel disease controls, 76; for rheumatoid arthritis, 40; for rheumatoid arthritis controls, 160; imputed at population mean = 0.