| Study area (ref) | Population | Prevalence rate (M+W) (95% CI) | Prevalence rate (M) (95% CI) | Prevalence rate (W) (95% CI) | Mean age at onset (y) |
| Japan | 614 725 | 0.8 (0.3–1.9) | 1.4 (0.4–3.6) | 0.3 (0.01–1.7) | NS |
| New South Wales, Australia | 5 995 544 | 1.9 (1.5–2.2) | 2.2 (1.7–2.8) | 1.6 (1.2–2.1) | 53.5 |
| SE England | 3 717 638 | 1.2 (0.9–1.7) | NR | NR | 54.4 |
| Vest-Agder, Norway | 155 464 | 7.7 (3.2–12.2) | 14.7 (7.3–26.4) | 5.0 (1.4–12.8) | 48 |
| Piemonte, Italy | 4 334 225 | 3.6 (3.0–4.2) | 5.0 (4.1–6.1) | 2.2 (1.7–2.9) | 59.6 |
M, men; NR, not reported; W, women.
Prevalence rates are per 100 000 population.