Table 3: Prevalence of dementia (%) and its subtype by 10 years age group and by study site.

Age 70–79Age 80–89Age 90 and older
Study name/site Prevalence in percentage
(95% CI)
AD/VaD ratioPrevalence in percentage
(95% CI)
AD/VaD ratio Prevalence in percentage
(95% CI)
AD/VaD ratio
(Study years) (Number of subjects screened)Number of cases:
all subtypes combined/AD/VaD
(Number of subjects screened)Number of cases:
all subtypes combined/AD/VaD
(Number of subjects screened)Number of cases:
all subtypes combined/AD/VaD

Hisayama (1985)3.41 (1.92–5.56) AD/VaD = 0.1319.50 (13.65–26.52)AD/VaD = 0.7557.14 (28.86–82.34)AD/VaD = 2.50
(440) 15/1/8(159) 31/6/8 8/5/2
Hisayama 992 3.35 (2.00–5.25) AD/VaD = 0.2213.39 (9.34–18.37)AD/VaD = 1.4446.43 (27.51–66.13)AD/VaD = 6.00
(537) 18/2/9(239) 32/13/9 13/6/1
Okinawa (1991-1992)3.67 (2.32–5.02)AD/VaD = 0.5914.93 (10.97–18.89)AD/VaD = 2.1036.83 (28.08–45.58)AD/VaD = 3.66
(1481)*45/16/27(619)*81/42/20 37/22/6
Hiroshima (1992–1996)5.67 (4.09–7.66)AD/VaD = 0.9319.04 (14.97–23.87)AD/VaD = 2.6441.67 (26.97–61.50)AD/VaD = 4.66
(741) 42/13/14( 75/45/17 25/14/3
Hisayama (1998)3.99 (2.65–5.76)AD/VaD = 1.7116.84 (12.76–21.59)AD/VaD = 1.9235.59 (23.55–49.13)AD/VaD = 3.33
(676) 27/12/7( 50/25/13 21/10/3
Tajiri (1998)5.18 (3.80–6.93)AD/VaD = N/A22.33 (17.37–28.26)AD/VaD = 1.5051.52 (30.00–82.51)AD/VaD = N/A
(908) 7/3/0# 22/12/8#( N/A
Hisayama (2005)
6.86 (5.13–8.94)AD/VaD = 2.4027.74 (20.50–29.37)AD/VaD = 1.8453.49 (42.41–64.32)AD/VaD = 1.71
(729) 50/24/10 95/46/25 46/24/14
Ama-cho study (2008)
6.7 (4.12–9.02)AD/VaD = 1.7517.8 (14.81–26.41)AD/VaD = 11.3341.3 (26.51–61.52)AD/VaD = 4.50
(432) 29/14/8 49/34/3 24/18/4

AD/VaD: the number of AD cases/the number of VaD cases.
#Based on subsample analysis with MRI results.
N/A: sample size is too small to perform the calculation (AD + VaD cases < 5).
*Random sampling was used for screening. reported is not weighted. Prevalence, proportions of subtypes of dementia, and AD/VaD ratio used weighted frequencies to show those of the population at large.