Table 1. Characteristics of the UK Biobank Sample Investigated in the Current Studya.
| Characteristic | Cases (n = 8276) | Controls (n = 194 000) | P value |
|---|---|---|---|
| Age at recruitment, mean (SD), y | 53.1 (7.9) | 56.7 (7.9) | <.001 |
| Depression | 813 (9.8) | 13 584 (7.)0 | <.001 |
| Anxiety | 301 (3.6) | 5688 (2.9) | <.001 |
| Eating disorders | 33 (0.4) | 558 (0.3) | <.001 |
| BMI, mean (SD) | 27.61 (5.39) | 26.98 (5.14) | <.001 |
| Townsend Deprivation Index at recruitment, mean (SD)b | −1.28 (3.00) | −1.56 (2.91) | <.001 |
| Age at menarche, mean (SD), y | 12.8 (1.7) | 13.0 (1.6) | <.001 |
| Ever taken oral contraceptive pill | 7065 (85.4) | 155 164 (80.0) | <.001 |
| Back pain for ≥3 mo | 2002 (24.2) | 32 461 (16.7) | <.001 |
| Stomach or abdominal pain for ≥3 mo | 1044 (12.6) | 9506 (4.9) | <.001 |
| Medication for pain relief, constipation, or heartburn | |||
| Aspirin | 707 (8.5) | 18 510 (9.5) | .002 |
| Ibuprofen | 1722 (20.8) | 29 524 (15.2) | <.001 |
| Paracetamol | 1561 (18.9) | 29 410 (15.2) | <.001 |
| Ranitidine | 61 (0.7) | 1384 (0.7) | .75 |
| Omeprazole | 284 (3.4) | 5315 (2.7) | <.001 |
| Laxatives | 143 (1.7) | 2648 (1.4) | .005 |
| None of the above | 3656 (44.2) | 100 073 (51.6) | <.001 |
| Pain type(s) experienced in last month | |||
| Headache | 2740 (33.1) | 43 601 (22.5) | <.001 |
| Facial pain | 97 (1.2) | 1610 (0.8) | <.001 |
| Neck or shoulder pain | 1240 (15.0) | 26 416 (13.6) | <.001 |
| Back pain | 827 (10.0) | 19 463 (10.0) | .91 |
| Stomach or abdominal pain | 317 (3.8) | 4177 (2.2) | <.001 |
| Hip pain | 195 (2.4) | 5786 (3.0) | .001 |
| Knee pain | 334 (4.0) | 9662 (5.0) | <.001 |
| Pain all over the body | 224 (2.7) | 3270 (1.7) | <.001 |
| None of the above | 2276 (27.5) | 74 314 (38.3) | <.001 |
| Ever diagnosed with IBS | 763 (9.2) | 11 182 (5.8) | <.001 |
| Frequency of discomfort or pain in abdomen in last 3 mo (0 indicating never to 6 indicating every day), median (IQR) | 2 (0-4) | 1 (0-3) | <.001 |
| Discomfort or pain occurring only during menstrual bleed | 47 (0.6) | 764 (0.4) | .01 |
| Abdominal discomfort/pain for ≥6 mo | 1405 (17.0) | 24 191 (12.5) | <.001 |
| Frequency of discomfort or pain getting better or stopping after a bowel movement (0 indicating never to 4 indicating always), median (IQR) | 2 (1-3) | 2 (1-3) | >.99 |
| More frequent bowel movements when abdominal discomfort or pain started (0 indicating never to 4 indicating always), median (IQR) | 1 (0-2) | 1 (0-1) | >.99 |
| Severity of current abdominal pain (0 indicating no pain to 10 indicating very severe pain), median (IQR) | 5 (3-7) | 4 (2-6) | <.001 |
| No. of days (of 10) with abdominal pain (0 indicating no days with pain to 10 indicating 10 d with pain), mean (SD) | 3.68 (2.83) | 3.05 (2.59) | <.001 |
| Length of menstrual cycle, mean (SD), d | 26.69 (7.46) | 26.85 (7.06) | .05 |
Abbreviations: BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); IBS, irritable bowel syndrome.
a
Data are presented as number (percentage) of study participants unless otherwise indicated. The difference between cases and controls was evaluated using a 2-tailed, unpaired t test for continuous traits and a χ2 test for categorical traits.
b
Percentage of non–car ownership, percentage of non–home ownership, percentage of unemployment, and percentage of overcrowding. z scores = (percentage – mean of all percentages)/SD of all percentages for a total of the 4 z scores.