Age distribution of people entering the HIV cohort, the percentage who were female, and the number of people who entered the reference cohort*
| Age (years) | HIV cohort Number (% of total) | Female (%) | Reference cohort Number | |
|---|---|---|---|---|
| 0–4 | 139 | (0.7) | 44.6 | 112 355 |
| 5–9 | 168 | (0.8) | 45.2 | 145 618 |
| 10–14 | 138 | (0.7) | 57.2 | 113 372 |
| 15–19 | 173 | (0.8) | 59.0 | 166 198 |
| 20–24 | 653 | (3.1) | 44.4 | 200 079 |
| 25–29 | 2136 | (10.1) | 43.9 | 264 771 |
| 30–34 | 4066 | (19.2) | 36.9 | 377 462 |
| 35–39 | 4792 | (22.6) | 29.6 | 444 962 |
| 40–44 | 3701 | (17.5) | 24.9 | 390 356 |
| 45–49 | 2228 | (10.5) | 20.6 | 329 573 |
| 50–54 | 1293 | (6.1) | 18.6 | 345 117 |
| 55–59 | 776 | (3.7) | 17.4 | 375 702 |
| 60–64 | 480 | (2.3) | 16.3 | 377 503 |
| 65–69 | 274 | (1.3) | 21.2 | 387 109 |
| 70–74 | 98 | (0.5) | 21.4 | 397 229 |
| 75–79 | 37 | (0.2) | 27.0 | 385 998 |
| 80–84 | 22 | (0.1) | 22.7 | 282 933 |
| 85+ | 33 | (0.2) | 45.5 | 202 159 |
| All ages | 21 207 | (100) | 30.2 | 5 298 496 |
Note that all eligible controls were used (there is no merit in discarding controls to equalise numbers in each age group); and that all analyses were done within strata (eg, the 112 355 controls aged 0–4 were compared with the 139 in the HIV cohort). The expected numbers in each stratum were then summed to give age-standardised comparisons of expected and observed numbers with MS in each cohort.
*The reference cohort consisted of people admitted with the following conditions coded under the Office of Population, Censuses and Surveys code (OPCS) edition 4 for operations and the ICD revision 10 for diagnoses: adenoidectomy (OPCS4 E20), tonsillectomy (F34+F36), appendectomy (H01–H03), total hip replacement (W37–W39), total knee replacement (W40–W42), cataract (ICD 10 H25), otitis externa/media (H60–H67), varicose veins (I83), haemorrhoids (I84), deflected septum, nasal polyp (J33+J34.2), inguinal hernia (K40), gallbladder disease (K80–K81), in–growing toenail and other diseases of nail (L60), sebaceous cyst (L72.1), bunion (M20.1), internal derangement of knee (M23).
MS, multiple sclerosis.