Trends in the Prevalence of Dementia in Japan

Table 1

Description of each study in Japan.

Study name/site (study years)	Sampling frame	Assessment protocol	Prevalence of all-cause dementia among those aged 65 and older:
			(1) Prevalence in percentage (95% CI)
			(2) Number of cases (all subtypes combined/AD/VaD)
			(3) AD percentage out of all dementia
			(4) AD/VaD ratio
Hisayama; (1985, 1992, 1998, and 2005)	Total residents aged ≥ 65 in the area: Year 1985: 𝑁=938; Year 1992: 𝑁=1231; Year 1998: 𝑁=1442; Year 2005: 𝑁=1711	Phase 1; Suspected dementia cases selected using Hasegawa dementia scale, neuropsychological tests, and ADL	Year 1985; (1) 6.7 (5.0–8.3); (2) 59/12/21; (3) 20.3%; (4) 0.57
	Study participants at Phase 1 (participation rates); Year 1985: 𝑁=887 (94.6%); Year 1992: 𝑁=1189 (96.6%); Year 1998: 𝑁=1437 (99.7%); Year 2005: 𝑁=1566 (91.5%); Sampling weights used to reflect prevalence of population at large?; (Yes/No): No	Phase 2; DSM-III-R, Karasawa’s criteria (supplementation), and Hachinski’s evaluation scale for cerebral ischemia in case vascular effect on dementia were considered to be too ambiguous to diagnose as VaD using the following guidelines: Hachinski’s ischemic score; <4.0—AD; ≥8—VaD; 5, 6, 7—mixed/other	Year 1992; (1) 5.6 (4.4–7.1); (2) 68/21/22; (3) 30.8%; (4) 0.95; Year 1998; (1) 7.1 (5.7–8.5); (2) 102/49/25; (3) 48.0%; (4) 1.96; Year 2005; (1) 12.5 (10.7–14.2); (2) 195/96/51; (3) 49.2%; (4) 1.89
Okinawa (1991-1992)	Randomly sampled one city from the urban districts and one town/village from the rural districts from each of 5 regions covering the entire Okinawa prefecture. Randomly selected approximately 17% of the residents from the selected cities and towns/villages in each region.	Phase 1; Pilot study was conducted (𝑁=789) to examine the best MMSE cut-point for screening. MMSE score of 16 had the maximum combination of sensitivity and specificity to identify the demented in the community; Selected those with MMSE ≤16 (𝑁=482)	(1) 6.7 (3.6–7.8); (2) 170/80/53; (3) 47.1%; (4) 1.51
	Study participants at Phase 1: 𝑁=3524; Sampling weights used to reflect prevalence of population at large?; (Yes/No): Yes	Phase 2 (𝑁=482); DSM-III-R for dementia, NINCDS-ADRDA for AD, and Hachinski’s ischemic score as a guideline for VaD
Hiroshima (Radiation effect research foundation Adult Health Survey ((RERF-AHS)) (1992–1996)	Residents in Hiroshima among the Original AHA cohort (atomicbomb survivors in Hiroshima and Nagasaki and their controls followed since 1958) evaluated by biennial physical exams between 1992 and 1996. Targeted 𝑁=2934	Phase 1; Subjects with CASI∗≤ 75 (𝑁=339) and controls with CASI > 75 (𝑁=276) were selected	(1) 8.5 (7.2–9.8); (2) 156/74/40; (3) 47.4%; (4) 1.85
	Study participants at Phase 1: 𝑁=2222; Sampling weights used to reflect prevalence of population at large?; (Yes/No): No	Phase 2 (𝑁=550); DSM-III-R for dementia, NINCDS-ADRDA for AD, ADDTC for ischemic vascular dementia, and DSM-III-R for VaD
Tajiri Project (1998)	All residents in Tajiri town aged ≥ 65, targeted 𝑁=3207	All (𝑁=1654) were evaluated by CDR & DSM-IV (not multistage sampling)	(1) 8.5 (7.2–9.9); Based on subtype analysis with MRI; (I) Using NINCDS-ADRDA, NINDS-AIREN; (2) 32/20/6; (3) 62.5%; (4) 3.33
	Study participants 𝑁=1654 Subsample selected for dementia subtype identification study, targeted 𝑁=564; Sampling weights used to reflect prevalence of population at large?; (Yes/No): No	MRI study: 564 selected randomly from 1654 above, of whom 497 participated in MRI study (dementia subtype identification study). Comparisons of prevalence of VaD using 3 different criteria: (1) DSM-IV for AD and VaD; (2) NINCDS-ADRDA for probable AD, NINDS-AIREN for possible AD with CVD and probable VaD; (3) ADDTC for probable ischemic vascular dementia	(II) Using DSM-IV for AD and VaD; (2a) 32/13/13 (2b) 32/18/8; (3a) 40.6% (3b) 56.2%; (4a) 1.00 (4b) 2.25; The difference between (a) and (b) above is due to diagnostic differences between assessors
Ama-cho (2008)	All residents in Ama-cho aged ≥ 65, targeted 𝑁=943	Phase 1 (𝑁=917); Suspected dementia cases selected through interviews with subjects and their informants, which assessed cognitive changes, psychiatric symptoms, personality changes, problem behaviors, activities of daily living, psychological and medical symptoms, and through assessments of the subjects’ medical history offered by the home doctors of the subjects	(1) 11.3 (9.1–13.2); (2) 104/66/16; (3) 63.5%; (4) 4.12
	Study participants 𝑁=917 (after excluding 23 subjects out of 943 subjects who resided out of town at the time of phase 1 interview); Sampling weights used to reflect prevalence of population at large?; (Yes/No): No	Phase 2 (𝑁=120); DSM-IV for dementia, NINCDS-ADRDA for AD, and NINDS-AIREN for VaD

∗CASI: The Cognitive Abilities Screening Instrument [19].