| Study population | Region | Midyear of study | No of patient-years | No of SAH patients | Incidence per 100 000 person years (95% CI) | Additional case finding methods‡ | % of patients with CT | Additional diagnostic criteria†† |
| Rochester39 | USA | 1955 | 331 081 | 29 | 8.8 (5.9 to 12.6) | adhjm | 0 | AB |
| Rochester39 | USA | 1965 | 451 611 | 52 | 11.5 (8.6 to 15.1) | adhjm | 0 | AB |
| Espoo17 | Finland | 1972 | 226 200 | 42 | 18.6 (13.4 to 25.1) | ae | 0 | B |
| Rochester39 | USA | 1975 | 543 561 | 61 | 11.2 (8.6 to 14.4) | adhjm | 27¶ | ABD |
| Espoo17 | Finland | 1979 | 273 700 | 33 | 12.1 (8.3 to 16.9) | ae | 11 | B |
| Copenhagen46 | Denmark | 1984 | 295 470 | 49 | 16.6 (12.3 to 21.9) | ak | 47 | ABE |
| Izumo city†27 | Japan | 1985 | 807 490 | 170 | 21.1 (18.0 to 24.5) | a | 99§ | ABC |
| Rochester39 | USA | 1985 | 617 554 | 43 | 7.0 (5.0 to 9.4) | adhjm | 85¶ | ABD |
| Finland17 | Finland | 1990 | 269 608 | 39 | 14.5 (10.3 to 19.8) | aeh | 60 | B |
| Izumo city†26 | Japan | 1990 | 496 074 | 123 | 24.8 (20.6 to 29.6) | ai | 100§ | BE |
| Asturias37 | Spain | 1991 | 417 033 | 28 | 6.7 (4.5 to 9.7) | b | 70 | ‡‡ |
| Ahmadi29 | Kuwait | 1992 | 291 199 | 4 | 1.4 (0.4 to 35.2) | ab | 100 | A |
| Novosibirsk35 | Russia | 1992 | 158 234 | 14 | 8.9 (4.8 to 14.8) | abehjm | 0** | BC |
| Auckland†31 | New Zealand | 1992 | 1 890 738 | 166 | 8.8 (7.5 to 10.2) | ae | 82 | ABC |
| Belluno22 | Italy | 1992 | 211 389 | 12 | 5.7 (2.9 to 9.9) | abefjk | 90 | AB |
| Sweden north42 | Sweden | 1993 | 8 212 800 | 984 | 12.0 (11.2 to 12.8) | abkh | 87 | ABC |
| L’Aquila21 | Italy | 1994 | 297 838 | 24 | 8.0 (5.2 to 12.0) | abcefj | 89¶ | AB |
| Shimokita†24 | Japan | 1994 | 899 910 | 198 | 22.0 (19.0 to 25.3) | ai | 100§ | AC |
| Izumo City25 | Japan | 1994 | 509 124 | 123 | 24.2 (20.1 to 28.8) | ai | 98 | ABC |
| Malmo45 | Sweden | 1995 | 2 674 144 | 197 | 7.4 (6.4 to 8.5) | abde | 89 | AB |
| Izumo city†27 | Japan | 1995 | 763 686 | 188 | 24.7 (21.2 to 28.4) | ai | 98 | ABC |
| Perth7 | Australia | 1995 | 134 000 | 4 | 3.0 (0.8 to 7.6) | abdfj | >78 | BC |
| Sweden south40 | Sweden | 1996 | 1 140 000 | 106 | 9.3 (7.6 to 11.2) | ai | 100¶ | ABC |
| Melbourne5 | Australia | 1996 | 133 816 | 12 | 9.0 (4.6 to 15.7) | bdg | 91¶ | AB |
| London11 | UK | 1996 | 938 132 | 74 | 7.9 (6.2 to 9.9) | abefj | 88¶ | AB |
| Vibo Valentia20 | Italy | 1996 | 179 186 | 12 | 6.7 (3.5 to 11.7) | abdejk | 96¶ | B |
| Dijon43 | France | 1996 | 429 264 | 12 | 2.8 (1.4 to 4.9) | abdeh | 96 | ‡‡ |
| Valle d’ Aosta44 | Italy | 1997 | 118 723 | 14 | 11.8 (6.4 to 19.8) | abdej | 97¶ | AB |
| Erlangen10 | Germany | 1997 | 202 900 | 12 | 5.9 (3.1 to 10.3) | abdejk | 96 | D |
| Kumamoto†23 | Japan | 1998 | 9 300 000 | 2115 | 22.7 (21.8 to 23.7) | bij | 100§ | AC |
| Martinique30 | Caribbean | 1998 | 360 000 | 20 | 5.6 (3.4 to 8.6) | abeijk | 93 | A |
| Scotland36 | UK | 1999 | 212 704 | 23 | 10.8 (6.9 to 16.2) | abhfl | 91 | B |
| Portugal north33 | Portugal | 1999 | 246 224 | 23 | 9.3 (5.9 to 14.0) | abdefhikm | 97 | B |
| Orebro41 | Sweden | 1999 | 123 503 | 11 | 8.9 (4.4 to 15.9) | abdefkm | 84 | AB |
| Tartu13 | Estonia | 2000 | 101 122 | 8 | 7.9 (3.4 to 15.6) | abei | 92 | B |
| Iqueque9 | Chile | 2001 | 396 712 | 15 | 3.8 (2.1 to 6.2) | abdefgh | 91 | AB |
| Tbilisi18 | Georgia | 2002 | 140 926 | 23 | 16.3 (10.3 to 24.5) | aehijl | 78§ | A |
| Barbados8 | Caribbean | 2002 | 239 068 | 7 | 2.9 (1.2 to 6.0) | abcdefh | 96 | B |
| Oxford12 | UK | 2003 | 181 084 | 16 | 8.8 (5.1 to 14.3) | abefk | 98¶ | AB |
SAH, subarachnoid haemorrhage.
*Studies listed in ascending order of midyear of data collection and are additional to those in the previous review.
†Studies based primarily on SAH, in contrast with general stroke studies.
‡Case finding methods. For inclusion, involvement of all hospitals in the region necessary and at least a or b. a = death certificates; b = general practitioners; c = rehabilitation; d = nursing homes; e = regular search; f = review radiology requests; g = media attention (campaign/newspaper); h = outpatient clinics, health centres; i = sudden deaths, very early death; j = emergency, ambulance, on call medical services; k = ICD-codes; l = door-to-door, home visit, social services, phone calls; m = autopsy reports.
§Studies providing the proportion of CT use in SAH patients exclusively, in contrast with % of CT in patients with stroke in general.
¶Studies not providing the exact proportion of patients with CT exclusively, but only the proportion of patients investigated with CT, autopsy or MRI.
**CT was available after 1992, and before 1992, all patients were diagnosed with lumbar puncture or autopsy.
††Additional diagnostic criteria, besides CT. For inclusion, at least A or B was necessary in pre-CT era or when CT percentage was below 90%. A = Lumbar puncture; B = autopsy; C = angiography; D = MRI; E = surgery.
‡‡Proportion of patients investigated with CT or diagnostic criteria unknown, but inclusion after discussion among authors of this review.