Table 1.
Characteristics of the Study Populationa
| Characteristic | Cases (n = 845) | Controls (n = 8450) | P Valueb |
|---|---|---|---|
| Demographics | |||
| Female sex | 465 (55.0) | 4650 (55.0) | …c |
| Age, median (IQR), y | 6 (4–8) | 6 (4–8) | … |
| Age category, y | |||
| 1–5 | 366 (43.3) | 3660 (43.3) | … |
| 6–10 | 367 (44.4) | 3670 (44.4) | |
| 11–15 | 112 (13.3) | 1120 (13.3) | |
| Country of origin | |||
| England | 660 (78.1) | 7189 (85.1) | <.001d |
| Northern Ireland | 62 (7.3) | 325 (3.9) | |
| Scotland | 78 (9.2) | 545 (6.5) | |
| Wales | 45 (5.3) | 391 (4.6) | |
| Townsend indexe | |||
| 1 | 179 (21.2) | 2157 (25.5) | <.001d |
| 2 | 161 (19.1) | 1657 (19.6) | |
| 3 | 159 (18.8) | 1596 (18.9) | |
| 4 | 173 (20.5) | 1578 (18.7) | |
| 5 | 146 (17.3) | 1186 (14.0) | |
| Missing | 27 (3.2) | 276 (3.3) | |
| Comorbidities | |||
| Personal autoimmunityf | 4 (0.5) | 16 (0.2) | |
| Celiac disease | 0 | 8 (0.1) | .10g |
| Thyroid disease | 1 (0.1) | 4 (<0.1) | |
| Type 1 diabetes mellitus | 3 (0.4) | 5 (0.1) | |
| Any infectionf | 754 (89.2) | 7185 (85.0) | <.001 |
| Any skin infectionf | 475 (56.2) | 3838 (45.4) | <.001 |
| External genitourinary | 65 (7.7) | 444 (5.3) | .003 |
| Herpes simplex | 18 (2.1) | 114 (1.4) | .07 |
| Molluscum contagiosum | 6.2 (7.3) | 516 (6.1) | .15 |
| Tinea | 67 (7.9) | 341 (4.0) | <.001 |
| Wart | 90 (10.7) | 609 (7.2) | <.001 |
| Varicella | 194 (23.0) | 1679 (19.9) | .03 |
| Other viral exanthem | 50 (5.9) | 311 (3.7) | .001 |
| Other skin and soft-tissue infection | 249 (29.5) | 1943 (23.0) | <.001 |
| Any other infectionf | 736 (87.1) | 6946 (82.2) | <.001 |
| Upper respiratory tract | 674 (79.8) | 6317 (74.8) | <.001 |
| Lower respiratory tract | 327 (38.7) | 2399 (28.4) | <.001 |
| Gastrointestinal | 163 (19.3) | 1504 (17.8) | .28 |
| Urinary tract | 52 (6.2) | 395 (4.7) | .05 |
| Other | 355 (42.0) | 3108 (36.8) | .002 |
| No. of infections, median (IQR) | 5 (2–10) | 4 (1–8) | <.001 |
| Antibiotic Exposures | |||
| Any antibiotic prescribed | 710 (84.0) | 6343 (75.1) | <.001 |
| Antianaerobic antibioticsf | 683 (80.8) | 6099 (72.2) | <.001 |
| Penicillins | 677 (80.1) | 6056 (71.7) | <.001 |
| Broad-spectrum penicillins | 109 (12.9) | 667 (7.9) | <.001 |
| Metronidazole | 4 (0.5) | 48 (0.6) | .73 |
| Clindamycin | 0 | 0 | … |
| Other antianaerobich | 0 | 5 (0.1) | … |
| Nonantianaerobic antibioticsf | 354 (41.9) | 2827 (33.5) | <.001 |
| Cephalosporins | 136 (16.1) | 946 (11.2) | <.001 |
| Macrolides | 254 (30.1) | 1988 (23.5) | <.001 |
| Sulfonamides | 107 (12.7) | 764 (9.0) | <.001 |
| Other nonantianaerobich | 6 (0.7) | 34 (0.4) | .20 |
| Antimalarial | 13 (1.5) | 88 (1.0) | .19 |
| Other antimicrobial exposurei | 72 (8.5) | 591 (7.0) | .10 |
| Maternal Variables | |||
| Maternal autoimmunityf | 150 (19.7) | 671 (8.8) | <.001 |
| Arthritis | 15 (2.0) | 35 (0.5) | <.001 |
| Celiac disease | 3 (0.4) | 18 (0.2) | .40 |
| Connective tissue disease | 2 (0.3) | 14 (0.2) | .72 |
| Diabetes | 2 (0.3) | 25 (0.3) | .81 |
| Inflammatory bowel disease | 12 (1.6) | 53 (0.7) | .01 |
| Multiple sclerosis | 1 (0.1) | 10 (0.1) | … |
| Psoriasis | 101 (13.3) | 270 (3.5) | <.001 |
| Thyroid disease | 26 (3.4) | 248 (3.2) | .81 |
| Uveitis | 8 (1.1) | 33 (0.4) | .04 |
| Maternal smoking | 285 (33.7) | 2364 (28.0) | .001 |
| Missing maternal smoking data | 96 (11.4) | 1067 (12.6) | … |
| Missing maternal data | 83 (9.8) | 804 (9.5) | … |
| Other Variables | |||
| Cesarean delivery | 119 (14.1) | 1224 (14.5) | .77 |
| Missing delivery data | 358 (42.4) | 3360 (39.8) | … |
| Hospitalizationf | 104 (12.3) | 863 (10.2) | .06 |
| Infection | 46 (5.4) | 347 (4.1) | .07 |
| Other | 71 (8.4) | 626 (7.4) | .29 |
| No. of outpatient visits in last 2 years,j median (IQR) | 5 (2–9) | 3 (0–7) | <.001 |
Abbreviation: IQR, interquartile range.
Data are presented as number (percentage) unless otherwise indicated.
All P values were obtained from univariable conditional logistic regression models.
Ellipses indicate data not applicable.
Overall χ2 test P value.
Geography-based deprivation index; higher index score means more deprived.
Some participants had more than one type.
Comparison of main category.
Other antianaerobic antibiotics include tetracyclines, glycopeptides (oral vancomycin), carbapenems, and cefoxitin (all other cephalosporins categorized as nonantianaerobic); other nonantianaerobic antibiotics include fluoroquinolones and all other antibiotic classes.
Other antimicrobial agents, including antifungal, antiviral, and antimycobacterial drugs.
Total outpatient visits per year for 2-year period starting 3 years before psoriasis diagnosis.