World Dementia
Council

Leading the Global Action
Against Dementia

Dementia
prevention in JapanAn independent review of evidence
submitted to the World Dementia Council
Tomo Takasugi and Katsunori Kondo

Produced in partnership with

About this paper
This paper was prepared by the authors to inform the World Dementia Council
about dementia risk factors and risk reduction efforts in Japan. It was written
independently and submitted as evidence to the WDC's project on presenting
a global evidence base for dementia friendly initiaitves.
The evidence submitted in this paper is solely the work of the authors andshould not be read as representing the views of any one individual on theWorld Dementia Council, nor any other individuals and organizations thathave contributed to or advised the project.

2 | Dementia prevention in Japan

Tomo Takasugi and Katsunori Kondo

About the authors
Tomo Takasugi MPH
Tomo Takasugi is a research officer at thesocial security and healthcare group of Sompo
Research Institute Inc. (Japan). Her research
theme is examining the association between
socioeconomic status and dementia onset inolder adults.
She has worked as a Japan overseas cooperation
volunteer in Tanzania, a senior researcher of
medical materials research and development,a senior consultant of pandemic influenza
preparation in Japan, and an international
public health specialist in Africa and the Middle
East. She obtained a masters degree in publichealth from the University of Sheffield (UK).

Katsunori Kondo MD, PhD
Dr Katsunori Kondo is the principal investigatorof the Japan Gerontological Evaluation Study(JAGES) initiative, which is one of the firstprospective cohort studies to investigate theinfluence of social determinants of health andcommunity social capital on health outcomesamong older people.
He is a professor of social epidemiology andhealth policy at the Department of Social
Preventive Medical Sciences, Center for
Preventive Medical Sciences and the Graduate
School of Medicine, Chiba University (Japan).
He is also head of department of gerontologicalevaluation, Center for Gerontology and Social
Science, National Center for Geriatrics andGerontology, Obu City (Japan).

3 | Dementia prevention in Japan

Tomo Takasugi and Katsunori Kondo

Contents
1.

Executive summary			

2.

Introduction				6

3.
		Dementia risk factors at 		
the individual level			7

4.
Dementia risk factors at 				
the social environment
		level			13

4 | Dementia prevention in Japan

5

Tomo Takasugi and Katsunori Kondo

Executive summary
Dementia risk factors include:
1. Those possessed by the individual (individual level risk factors) and;2. Those present in the social environment (social environment level risk factors).
To create dementia-friendly communities, efforts must be made to decrease risk
factors on both levels. Studies have revealed individual level dementia risk factors
include psychological and social factors in addition to biological factors. Biologicalfactors that suggested lower dementia risk include having many teeth left;
following a Japanese diet that includes rice, miso soup, seaweed, green and yellow
vegetables, fish, and green tea; high intake volume of milk and dairy products;
daily consumption of green tea; walking one hour or more per day; and having
a high walking speed. From the psychological perspective, maintaining healthy
psychological and social conditions may be more important for dementia prevention
than making efforts to improve physical health. Appropriate sleep levels were also
shown to lower dementia risk. Social and environmental activities linked to lower
dementia risk included shopping, gardening, reading newspapers, using computers,
living together with family, interacting with friends, participating in community
groups, and being employed. People who were the victims of natural disasters withweak community social cohesion had slower dementia progression if they lived incommunities with strong community social cohesion overall. People who grew up insocioeconomically poor situations had the highest subjective dementia risk.
On the social environment level, regional comparisons were conducted using theresults of Japan Gerontological Evaluation Studies (JAGES). Comparisons revealed
discrepancies in built environments and ease of social participation. It was shown
to be possible for a person to lower their dementia risk by moving to an area withhigher exercise group participation rates, even when other conditions remained
unchanged. Namely, this means one condition for Age-Friendly and Dementia Cities
is having ample opportunities for social participation. In addition, intervention
studies showed that it is possible to conduct community-building in a way thatencourages social participation. Among the people in such communities who started
to engage in social participation, dementia and the risk of needing long-term care
were prevented. In the future, we look forward to efforts for creating Dementia
Friendly and Dementia Preventing Communities by using regional diagnostic
indicators to evaluate the degree to which social participation is encouraged.

5 | Dementia prevention in Japan

Tomo Takasugi and Katsunori Kondo

Introduction
Dementia risk factors include:
1. Those possessed by the individual (individual level risk factors) and;2. Those present in the social environment (social environment level risk factors).
To create dementia-friendly communities, efforts must be made to decrease risk
factors on both levels. The purpose of this report is to review dementia risk factors
reported in Japan, the country where population aging has advanced the most.
We searched the Japan Medical Abstracts Database to find Japanese articles.
The retrieval style was set to “elderly people AND (dementia risk reduction OR
dementia risk).” Results that included non-Japanese people, included fewer than
400 participants,1 or that described specific diseases or medical treatments were
removed. For English articles, we searched on PubMed. The retrieval style on
PubMed was set to “dementia AND older Japanese.” The search was limited to
articles published in English within the last ten years. Articles that did not fit theabove-mentioned selection criteria were removed based on titles and abstracts. We
also conducted a handsearch after obtaining the opinions of experts in the field. We
sorted articles by explanatory variables handled and main findings on dementia risk
factors.

1. Haneda M, Noda M, Origasa H,
et al. : Japanese Clinical Practice
Guideline for Diabetes 2016. Journalof Diabetes Investigation, 9(3):657697(2018).

6 | Dementia prevention in Japan

Tomo Takasugi and Katsunori Kondo

Dementia risk factors at theindividual level
Studies have revealed individual level dementia risk factors include psychologicaland social factors in addition to biological factors. Study endpoints linked withdementia risk include biological factors like number of teeth remaining, adherence
to a Japanese diet, consuming milk and dairy products, and daily walking duration;
psychological factors like depression; and social factors like social participation andsocial support. Below, we will introduce:
1. Biological factors;
2. Psychological factors, and;3. Social and environmental factors.

Biological factors
Missing teeth; diet; milk and dairy intake volume; green tea, black tea, and coffee
intake volume; supplement intake volume; daily routines and illnesses; and timespent walking have all been linked with dementia risk. Results on these topics havebeen obtained as described below.
Oral cavity health
A four-year longitudinal Aichi Gerontological Evaluation Study (AGES) with
4,425 participants showed that dementia risk was higher for people with
dentures who were missing most of their teeth compared to people with 20 ormore teeth remaining (hazard ratio HR = 1.85, 95 per cent CI:1.04-3.31) andfor people without family dentists compared to people with family dentists(HR = 1.44, 95 per cent CI:1.04-2.01). It also showed that using dentures for
those with no teeth remaining lowered dementia risk by 40 per cent.2 A fiveyear longitudinal study conducted in Hisayama Town, Fukuoka Prefecturewith 1,566 participants aged 60 and over reported a higher dementia risk forpeople with 1 to 9 teeth (HR = 1.81, 95 per cent CI:1.11-2.94) and 10 to 19 teeth(HR = 1.62, 95 per cent CI: 1.06-2.46) compared to people with 20 or moreteeth remaining.3
Diet and nutrition
A cross-sectional study was conducted on the diets of 635 subjects aged 69 to
71 years living in Itami and Asago in Hyogo Prefecture and the Itabashi andNishitama districts in Tokyo. A significant association was found between
cognitive decline and diets high in foods of plant origin and fish, such as
vegetables, soy products, seaweed, mushrooms, potatoes, fruit, and greentea (β = 0.41, 95 per cent CI:0.33-0.79 using scores from Japan’s version of the

7 | Dementia prevention in Japan

2. Yamamoto T, Kondo K, Hirai
H, et al. : Association Between
Self-Reported Dental Health Status
and Onset of Dementia: A 4-Year
Prospective Cohort Study of Older
Japanese Adults from the Aichi
Gerontological Evaluation Study(AGES) Project. Psychosomatic
Medicine, 74(3):241-248(2012).
3. Takeuchi K, Ohara T, Furuta
M, et al. : Tooth Loss and Risk
of Dementia in the Community:
the Hisayama Study. Journal of
the American Geriatrics Society,65(5):e95-e100(2017).

Tomo Takasugi and Katsunori Kondo

Montreal Cognitive Assessment (MoCA-J), an examination for scoring Mild
Cognitive Impairment (MCI)). However, no association was found between
cognitive function and diets based on rice and miso soup and animal foodproducts.4
Next is the results of longitudinal studies. A 5.7-year longitudinal study with
14,402 participants living in Osaki City, Miyagi Prefecture showed that people
with diets high in Japanese food had a lower dementia risk compared to thosewith diets low in Japanese food based on nine items: rice, miso soup, seaweed,
pickled vegetables, green and yellow vegetables, fish, green tea, beef and pork,
and coffee (HR = 0.80, 95 per cent CI: 0.66-0.97).5 A 17-year longitudinal study
that followed 1,081 participants aged 60 and over in Hisayama Town, Fukuoka
Prefecture showed the subgroup with the highest intake volume of milk anddairy products had lower dementia risk particularly for Alzheimer's disease
compared to the subgroup with the lowest intake volume (HR = 0.63, 95 percent CI:0.41-0.98),6 and that the subgroup with the highest intake volume ofpotassium, calcium, and magnesium had lower dementia risk compared tothe subgroup with the lowest intake volume (HR = 0.20, 95 per cent CI:0.07–0.56).7 A ten-year longitudinal study that followed 570 participants aged
60 to 81 years in Obu City and Higashiura Town in Aichi Prefecture foundthat decreases in cereal intake volume of 108 grams per day and increases
in the intake volume of milk and dairy products of 128 grams per day had
the potential to reduce the risk of cognitive decline for Japanese women.8 A
4.9-year longitudinal study that followed 723 participants aged 60 and overin Nanao City’s Nakajimachi area in Ishikawa Prefecture showed a lower
incidence of dementia or MCI for people who drank green tea daily comparedto people who drank no green tea whatsoever (odds ratio: OR = 0.26, 95 percent CI:0.06-1.06).9 In a seven-year longitudinal study with 918 participantsin the town of Tone in Ibaraki Prefecture, those who took supplements (n-3polyunsaturated fatty acids, dried ginkgo biloba extract, lycopene) for three
years had a lower risk of developing Alzheimer's disease (HR = 0.69, 95 percent CI:0.47-0.92).10 Meanwhile, a 5.7-year longitudinal study that followed
14,402 participants in Osaki City, Miyagi Prefecture showed no significant link
between diets heavy in animal and dairy products and dementia risk,5 andthe aforementioned 4.9-year longitudinal study that followed 723 participants
aged 60 and over in Nanao City’s Nakajimachi area in Ishikawa Prefecturereported no significant link between tea and coffee and the risk of dementia or
MCI.9
Physical activity
A cross-sectional study with 1,552 participants in Sasaguri Town in Fukuoka
Prefecture examined associations between five physical fitness measures(handgrip strength, leg strength, sit-to-stand rate, gait speed, and oneleg stand time) and cognitive function. It showed that physical fitness has
the potential to be a marker for low cognitive function.11 In the National
Center for Geriatrics and Gerontology Study of Geriatric Syndromes, a crosssectional study of 9,683 participants with a mean age of 73.6 years, a higher
prevalence of Motoric Cognitive Risk Syndrome (MCR) (a predementia

8 | Dementia prevention in Japan

4. Okubo H, Inagaki H, Gondo Y,
et al. : Association between dietary
patterns and cognitive function
among 70-year-old Japanese elderly:a cross-sectional analysis of the
SONIC study. Nutriton Journal,
16(1):56(2017).
5. Tomata Y, Zhang S, Sugiyama K,
et al. : Changes in time spent walking
and the risk of incident dementia inolder Japanese people: the Ohsaki
Cohort 2006 Study. Age and Ageing,
46(5):857-860(2017).
6. Ozawa M, Ohara T, Ninomiya T,
et al. : Milk and dairy consumption
and risk of dementia in an elderly
Japanese population: the Hisayama
Study. Journal of the American
Geriatrics Society. 62(7):12241230(2014).
7. Ozawa M, Ninomiya T, Ohara T,
et al. : Self-reported dietary intake ofpotassium, calcium, and magnesium
and risk of dementia in the Japanese:
the Hisayama Study. Journal of
the American Geriatrics Society,60(8):1515-1520(2012).
8. Otsuka R, Kato Y, Nishita Y, et al.
: Cereal Intake Increases and Dairy
Products Decrease Risk of Cognitive
Decline among Elderly Female
Japanese. The journal of preventionof Alzheimer's disease, 1(3):160167(2014).
9. Noguchi-Shinohara M, Yuki S,
Dohmoto C, et al. : Consumptionof green tea, but not black tea or
coffee, is associated with reduced
risk of cognitive decline. PLoS One,9(5):e96013(2014).
10. Bun S, Ikejima C, Kida J, et al. :A combination of supplements may
reduce the risk of Alzheimer's diseasein elderly Japanese with normal
cognition. Journal of Alzheimer’s
Diseaese, 45(1):15-25(2015).
11. Narazaki K, Matsuo E, Honda T,
et al. : Physical Fitness Measures as
Potential Markers of Low Cognitive
Function in Japanese CommunityDwelling Older Adults without
Apparent Cognitive Problems.
Journal of Sports and Medicine,13(3):590-596(2014).

Tomo Takasugi and Katsunori Kondo

syndrome characterized by slow gait and cognitive abnormalities) was seen
with advancing age with no significant difference between men and women.
Lifestyle factors and diseases associated with increased risk of MCR werediabetes (adjusted odds ratio [OR] = 1.47, P = 0.001), depressive symptoms (OR= 3.57, P < 0.001), falls (OR = 1.45, P < 0.001), obesity (OR = 1.26, P = 0.018) andphysical inactivity (OR = 1.57, P < 0.001).12
A 5.7-year longitudinal study with 6,909 participants living in Osaki City,
Miyagi Prefecture showed that dementia risk was lower for participants
who walked for one hour or more per day compared to those who walked
30 minutes or less per day (HR = 0.72, 95 per cent CI:0.53–0.97).13 A 12year longitudinal study conducted by the Tokyo Metropolitan Institute ofGerontology involving 1,686 participants aged 65 to 90 years showed thatparticipants with lower gait speeds had a dementia risk 3.46 times higher
than those with higher gait speeds (95 per cent CI:1.88–6.40) and those withshorter step lengths had a dementia risk 2.12 times higher than those withlonger step lengths (95 per cent CI:1.29–3.49).14
As described above, a lower dementia risk was observed among people with a greaternumber of remaining teeth,2,3 people that consumed Japanese foods including rice,miso soup, seaweed, green and yellow vegetables, fish, and green tea,5 people withgreater milk and dairy consumption,6 people who drank green tea daily,9 people whowalked one hour or more per day,13 and people with high gait speeds.14

Psychological factors
The following results have been obtained about the effects of psychological health,mental health, and sleep times on dementia risk.
Psychological and mental healthIn a five-year longitudinal AGES study with 2,340 participants, psychologicalor social elements present among many of the participants that did not
develop dementia included having a hobby (OR = 2.27, 95 per cent CI:1.67–
3.10), subjectively feeling healthy (OR = 2.00, 95 per cent CI:1.48–2.73), notsuffering depression (OR = 1.91, 95 per cent CI:1.36–2.69), and independently
conducting Instrumental Activities of Daily Living (IADLs) (OR = 2.56, 95
per cent CI:1.84–3.56).15 Physical activities among that subgroup included
receiving physical check-ups (OR = 1.71, 95 per cent CI:1.25–2.35) and walking
for 30 minutes or more per day (OR = 1.54, 95 per cent CI:1.14–2.16).15 A fouryear AGES longitudinal study with 14,286 participants showed that men withpositive emotions had a 50 per cent lower risk and women had a 69 per centlower risk of developing dementia compared to participants without positive
emotions.16

12. Doi T, Verghese J, ShimadaH, et al. : Motoric Cognitive Risk
Syndrome: Prevalence and Risk
Factors in Japanese Seniors. Journalof the American Medical Directors
Association, 16(12):1103.e11211105(2015).
13. Tomata Y, Zhang S, Sugiyama K,
et al. : Changes in time spent walking
and the risk of incident dementia inolder Japanese people: the Ohsaki
Cohort 2006 Study. Age and Ageing,
46(5):857-860(2017).
14. Taniguchi Y, Kitamura A, Seino S,
et al. : Gait Performance Trajectories
and Incident Disabling Dementia
Among Community-Dwelling Older
Japanese. Journal of the American
Medical Directors Association,
18(2):192.e113-192.e120(2017).
15. 竹田徳則, 近藤克則, 平井寛, ほか. : 地

域在住高齢者の認知症発症と心理・社会的側面との関連. 作業療法, 26(1):55-

65(2007).

16. Murata C, Takeda T, Suzuki K,
et al. : Positive affect and incident
dementia among the old. Journal of
Epidemiological Research, 2(1):118124(2015).

9 | Dementia prevention in Japan

Tomo Takasugi and Katsunori Kondo

Dementia risk and sleep
A ten-year longitudinal study with 1,517 participants in Hisayama Town,
Fukuoka Prefecture found a higher dementia risk for subjects with daily sleep
duration of five hours or less (HR = 2.64, 95 per cent CI:1.38–5.05) and 10
hours or more (HR = 2.23, 95 per cent CI:1.42–3.49) compared to subjects withdaily sleep duration of 5 to 6.9 hours. It also showed that subjects who usedhypnotics had higher dementia risk than those who did not (HR = 1.66, 95 percent CI:1.09–2.53).17
As described above, longitudinal studies suggested that maintaining better
psychological health and social circumstances may be more important for
preventing dementia than activities undertaken to improve physical health15 andthat appropriate daily sleep duration lowers dementia risk.17

Social and environmental factors
The following findings have been made about the associations between dementia
risk and cognitive activity, social participation, social relationships, social support,
and socioeconomic status.
Cognitive activities and hobbies
A cross-sectional study conducted in Obu City and Nagoya City in Aichi
Prefecture with 5,300 participants with a mean age of 75 showed thatparticipants who engaged in five cognitive activities other than board games(reading books and newspapers, writing diaries and letters, doing crossword
puzzles, using computers, and keeping track of household expenses) had 35
per cent to 67 per cent fewer incidences of cognitive impairment. Participants
who engaged in cognitive activities less than once per week had the highest
risk of cognitive impairment.18
A longitudinal study that followed 4,564 participants in Obu City, Aichi
Prefecture for 3.6 years showed lower dementia risk for participants who
engaged in conversations daily (HR = 0.56, 95 per cent CI: 0.35–0.89), drove(HR = 0.63, 95 per cent CI:0.45–0.88), went shopping (HR = 0.57, 95 per cent
CI:0.34–0.96), and did gardening (HR = 0.71, 95 per cent CI:0.54–0.94).
However, these associations may vary due to age and sex.19 Similarly, alongitudinal AGES study that followed 9,720 participants for three years
showed a higher dementia risk for those with impaired ability to conduct
everyday activities like going out, shopping, and cooking for both men (HR= 1.80, 95 per cent CI:1.22–2.66) and women (HR = 2.23, 95 per cent CI:1.60–
3.13) and for men without artistic hobbies (HR = 1.99, 95 per cent CI:1.23–3.22)
and women without athletic hobbies (HR = 1.92, 95 per cent CI:1.15–3.19).20
A study conducted by the Chubu Regional City Municipality that followed
558 participants for six years showed a higher incidence rate of dementia forpeople who do not read newspapers compared to those who did (OR = 2.12, 95
per cent CI:1.32–3.40).21

10 | Dementia prevention in Japan

17. Ohara T, Honda T, Hata J, et al.
: Association Between Daily Sleep
Duration and Risk of Dementia andMortality in a Japanese Community.
Journal of the American Geriatrics
Society, 66(10):1911-1918(2018).
18. Kurita S, Doi T, Tsutsumimoto
K, et al. : Cognitive activity in asitting position is protectively
associated with cognitive impairment
among older adults. Geriatrics &Gerontology International, 19(2):98102(2019).
19. Shimada H, Makizako H, Lee S,
et al. : Lifestyle activities and therisk of dementia in older Japanese
adults. Geriatrics & Gerontology
International, 18(10):14911496(2018).
20. 竹田徳則, 近藤克則, 平井寛. : 地域在住高齢者における認知症を伴う要介護認定の心理社会的危険因子AGESプロジェクト
3年間のコホート研究. 日本公衆衛生雑誌,
57(12):1054-1065(2010).

21. 矢内悠里, 篠原亮次, 杉澤悠圭, ほか. :社会とのかかわりと認知症発症との関連性の研究. 日本保健福祉学会誌, 18(2):21-

28(2012).

Tomo Takasugi and Katsunori Kondo

Social participation, social relationships, and social support
A cross-sectional study that followed 929 participants in Tsuru City’s
Shimoyaji Ward in Yamanashi Prefecture showed a negative association
between cognitive decline and participation in regional organization activities(OR = 0.57, 95 per cent CI:0.29-1.11) and socioeconomic activities (OR = 0.47,
95 per cent CI:0.20-1.10) among men and volunteer activities (OR = 0.27, 95
per cent CI:0.09-0.80) among women. There were links between depression
and these associations.22
An AGES longitudinal study that followed 13,850 participants for 9.4 years
showed a higher risk of dementia onset among the young-old elderly who did
not engage in local activities compared those who engaged in local activities
in non-leadership roles (HR = 1.22, 95 per cent CI:1.02–1.46) and a lower risk
for those in leadership roles compared to those in non-leadership roles (HR =0.81, 95 per cent CI:0.65–0.99).23 In an AGES longitudinal study that followed
13,984 participants for 9.4 years, dementia risk was 11 per cent to 17 per centlower for those who were married, engaged in mutual support with co-residing
family members, had contact with friends, participated in community groups,
and were employed. Participants who fulfilled all five of these conditions had
a lower dementia risk (HR = 0.54,P < 0.001).24 In an AGES longitudinal study
that followed 14,088 participants for 9.4 years, providing emotional support
to coresiding family members was shown to lower dementia risk for men (HR= 0.83, 95 per cent CI:0.72–0.95) while providing emotional support to noncoresiding family members and relatives (HR = 0.87, 95 per cent CI:0.76–0.98)
and receiving emotional support from friends and neighbors (HR = 0.85,
95 per cent CI:0.74–0.97) to lowered dementia risk for women.25 An AGES
longitudinal study that followed 12,085 participants for ten years reported
that those who interacted with non-cohabitant people less than once permonth were more likely to acquire functional disability requiring long-termcare level two (HR = 1.37, 95 per cent CI:1.16–1.61) or dementia accompanying
functional disability (HR = 1.45, 95 per cent CI:1.21–1.74) and suffer premature
death (HR = 1.34, 95 per cent CI:1.16–1.55) compared to those that interactedwith non-cohabitant people daily. However, there was no significant
association found for those who engaged in social interaction once or more
per week. In other words, this study showed that face-to-face and non-face-toface interaction with people other than cohabitants less than once per week
may lead to a state requiring long-term care or dementia.26
In a 3.2-year longitudinal study that followed 3,560 participants in Iwanuma
City, Miyagi Prefecture, among those whose community social cohesion
fell one point on a five-point scale after the Great East Japan Earthquake,the severity of cognitive disability increased by 0.04 points (where level
one corresponds to independence and level eight corresponds to needing
specialized medical treatment) per level of housing damage experienced on a
five-point scale. The severity of cognitive disability was 0.07 points lower foreach point the respondent scored in community social cohesion.27

11 | Dementia prevention in Japan22. 根本裕太, 佐藤慎一郎, 高橋将記, ほ
か. : 地域高齢者における認知機能低下の関
連要因 横断研究. 日本老年医学会雑誌,

54(2):143-153(2017).

23. Nemoto Y, Saito T, Kanamori S, etal. : An additive effect of leading rolein the organization between social
participation and dementia onset
among Japanese older adults: theAGES cohort study. BMC Geriatrics,
17:297(2017).
24. Saito T, Murata C, Saito M, etal. : Influence of social relationshipdomains and their combinations on
incident dementia: a prospective
cohort study. Journal of Epidemiology
and Community Health, 72(1):712(2018).
25. Murata C, Saito T, Saito M, etal. : The Association between Social
Support and Incident Dementia:
A 10-Year Follow-Up Study inJapan. International Journal ofEnvironmental Research and Public
Health, 16:16(2):239(2019).
.
26. 斉藤雅茂, 近藤克則, 尾島俊之, ほか.
: 健康指標との関連からみた高齢者の社会的孤立基準の検討10年間のAGESコホートより. 日本公衆衛生雑誌, 62(3):95-

105(2015).

27. Hikichi H, Tsuboya T, Aida J,
et al. : Social capital and cognitive
decline in the aftermath of a natural
disaster: a natural experimentfrom the 2011 Great East Japan
Earthquake and Tsunami. The Lancet
Planetary health, 1(3):e113(2017).

Tomo Takasugi and Katsunori Kondo

The effects of socioeconomic status
A retrospective longitudinal study with 75,358 respondents in Adachi Ward,
Tokyo showed a greater likelihood of subjective dementia symptoms for
elderly people with the lowest childhood socioeconomic status comparedto elderly people with the highest childhood socioeconomic status. In
particular, the older subgroup (OR = 1.46, 95 per cent CI:1.21-1.76) had agreater likelihood of subjective dementia symptoms compared to the younger
subgroup (OR = 1.32, 95 per cent CI:1.04-1.68). However, there were nointeractions between childhood socioeconomic status and sex. It is possiblethat this difference was caused by respondents’ early life experiences or theeffects of social and historic events (such as World War II, the chaotic period
after the war, or Japan’s period of rapid economic growth).28
As described above, activities associated with lower dementia risk were shopping,19,20
gardening,19,20 reading newspapers,18,21 using computers,18 interacting withcoresiding family members and friends, participating in community groups, andbeing employed.24 In areas struck by natural disaster, living in communities withstrong community social cohesion had a protective effect from dementia symptom
progression even for individuals with weak community social cohesion.27 Elderly
people with the lowest childhood socioeconomic status had the highest risk of
subjective dementia symptoms.28
As was seen in prior research conducted overseas, there was an abundance of social
epidemiology research in Japan that found associations between dementia risk
and factors such as community social cohesion. It was also evident that studies
conducted in disaster-stricken regions and similar areas are unique.

28. Murayama H, Sugiyama M,
Inagaki H, et al. : The Differential
Effects of Age on the Association
Between Childhood Socioeconomic
Disadvantage and Subjective
Symptoms of Dementia Among
Older Japanese People. Journal of
Epidemiology, JE20180002-1 (2018).

12 | Dementia prevention in Japan

Tomo Takasugi and Katsunori Kondo

Dementia risk factors at thesocial environment level
While there are various aspects to dementia risk factors at the social environment
level, evidence recently accumulated in Japan can be broadly classified into two
categories: the built environment and efforts to create environments that encouragesocial participation.

The built environment as a dementia risk factor
It has been reported that poor access to neighborhood food stores may affect health.
A three-year longitudinal study originating from the 2010 JAGES survey that was
conducted among 49,511 participants aged 65 and over from 31 municipalities
showed that poor access to neighborhood food stores may increase dementia
risk. Compared to respondents who said “There are many food stores in myneighborhood,” respondents who said “There are no food stores in my neighborhood
whatsoever” had a higher dementia risk (HR = 1.65, 95 per cent CI:1.40-1.93).
Compared to the subgroup that had the most food stores within a 500-meter radiusof their residential area, the subgroup with fewer food stores had higher dementia
risk (HR = 1.51, 95 per cent CI:1.34-1.69). Many elderly people named visitingneighborhood stores as a reason for outings and there is data that over half of elderly
people visit food stores three to four times per week. Ready access to neighborhood
food stores may also increase the likelihood that shopping trips are made on foot.
Good access to neighborhood food stores may promotes outings and contribute to
reducing dementia risk. This study demonstrated that access to food stores may be
important for dementia rather than access to restaurants or convenience stores.29
Additionally, a cross-sectional study of the JAGES 2010 survey that included 83,384
respondents aged 65 and over from 31 municipalities confirmed that people withfew neighborhood food stores had a lower intake frequency of 2.7 times per monthfor vegetables and 0.9 times per month for meat compared to people with manyneighborhood food stores nearby.30
Also, a study showed that poor neighborhood food access may be a mortality riskin addition to a dementia risk. A three-year longitudinal study was conductedwith 49,511 people who participated in the 2010 JAGES survey aged 65 and overin 31 municipalities who had been asked about the number of neighborhood foodstores with fruits and vegetables. Elderly people who did not drive for outings that
responded “There are not many” had a higher mortality risk (HR = 1.59, 95 per cent
CI:1.20-2.10) compared to those who responded “There are many.”31

29. Tani Y, Suzuki N, Fujiwara T, etal. : Neighborhood Food Environmentand Dementia Incidence: the Japan
Gerontological Evaluation Study
Cohort Survey. American Journal ofPreventive Medicine, 56(3):383392(2019).
30. Yamaguchi M, Takahashi K,
Hanazato M, et al. : Comparisonof Objective and Perceived Accessto Food Stores Associated with
Intake Frequencies of Vegetables/
Fruits and Meat/Fish among
Community-Dwelling Older
Japanese. International Journal ofEnvironmental Research and Public
Health, 16(5):772(2019).
31. Tani Y, Suzuki N, Fujiwara T, etal. : Neighborhood food environment
and mortality among older Japanese
adults: results from the JAGES
cohort study. International Journalof Behavioral Nutrition and Physical
Activity, 15:101(2018).

13 | Dementia prevention in Japan

Tomo Takasugi and Katsunori Kondo

Dementia risk factors in environments that promote opportunities for social
participation
Dementia risk factors in observational studies
A cross-sectional JAGES study that included 88,370 participants from 30
municipalities reported a nearly threefold difference in IADL decline between
municipalities (Figure 1). Municipalities had lower rates of IADL decline themore residents participated in hobbies, sports, or volunteer groups. This
demonstrated that developing communities with population strategies may
result in lower dementia risk and prevent IADL decline.32

Figure 1: Ratio of subjects with IADL decline per municipality (limited to early
elderly subgroup)
X-axis: 		
Ratio of subjects with IADL decline (per cent)Y-axis: 		
Municipality (n = 53)
Top left: 		
City (many)
Top right:
Suburb, rural village (many)
Blue box:
City: Ordinance-designated city wards
Red/white box: Municipalities with land population density 1000 people and			overWhite box:
Rural village: Municipalities with land population density			less than 1000 people
Right axis:
2.9 times: highest, average, lowest
To investigate if this disparity can be accounted for by tallying at-risk
individuals or if it persists even when statistically accounting for the effects
of individual level factors, a multilevel analysis was conducted on 30,587
elderly people from 24 municipalities who participated in the 2010 and 2013
JAGES surveys. The results of that analysis confirmed there was a 10 per
cent lower risk of IADL decline over three years for communities with highsocial participation in the cross-sectional study even when accounting forfactors on the individual level (OR = 0.90, 95 per cent CI:0.84-0.96). IADL

14 | Dementia prevention in Japan

32. 加藤清人, 近藤克則, 竹田徳則, ほか. :手段的日常生活活動低下者割合の市町村間格差は存在するのかJAGESプロジェクト. 作
業療法, 34(5):541-554 (2015).

Tomo Takasugi and Katsunori Kondodecline has been associated with dementia risk, so it may be possible to reduce
dementia risk through community development initiatives that increase social
participation among the elderly.32
Also, in a cross-sectional analysis of 180 respondents to the 2013 JAGES
survey aged 70 to 74 years residing in Higashikawa, Higashikagura, and Biei in
Hokkaido, cognitive function scores were 0.63 per cent higher for every typeof social activity each individual participated in. It also showed that individual
cognitive function scores may be kept 3.4 per cent higher as the average
number of area-level social activities available in the community increases
by one. These findings suggest that in addition to social participation on
the individual level, abundant area-level social activities may help maintaincognitive function among elderly people.34
In addition, a six-year longitudinal study originating from the 2010 JAGES
survey was conducted among 40,308 participants from 16 municipalities in
346 regions. It showed that cognitive decline risk for elderly people in a region
decreased by 8 per cent as exercise group participation increased by 10 per
cent of the elderly population in that region (HR = 0.92, 95 per cent CI:0.860.99).34
A cross-sectional study to examine the mechanism of that protective effectanalyzed 74,681 participants in the 2010 JAGES survey who lived in 39
municipalities and 516 regions across 12 prefectures. It found that the riskof depressive symptoms decreased for all elderly people living in a region by
11 per cent for men (Prevalence Ratio: PR = 0.89, 95 per cent CI:0.85-0.92)
and 4 per cent for women (PR = 0.96, 95 per cent CI:0.92-0.99) as the elderly
population participation rate in exercise groups increased by 10 per cent. This
study showed that in regions with high participation rates in exercise groups
among elderly people, the risk of depressive symptoms – a dementia risk –was lowered even among elderly people in the region who did not participate
in exercise groups.35 This finding was reflected in a three-year longitudinal
JAGES study that followed 29,065 elderly people in 295 school districts which
confirmed a tendency for the development of depressive symptoms to be 7 percent lower among men (OR = 0.93, 95 per cent CI:0.88-0.99)35 and 6 per centlower among women (OR = 0.94, 95 per cent CI:0.88-0.997) as the participation
rate in community groups and exercise groups increased by 6 per cent.36
Developing a regional diagnostic index of dementia risk factors
As described above, regional disparities in dementia risk have been verified
according to differences in factors at the social environment level, particularlyease of social participation. Furthermore, research has advanced on diagnostic
indicators for assessing dementia risk levels per region.
The World Health Organization (WHO) declared the decade starting in 2020
to be the Decade of Healthy Aging and momentum is building towards that
goal. Efforts to develop and use Indicators for Age Friendly Communities areadvancing using results generated by JAGES research. Specifically, a JAGES

15 | Dementia prevention in Japan

33. Fujihara S, Tsuji T, Miyaguni
Y, et al. : Does Community-Level
Social Capital Predict Decline in
Instrumental Activities of Daily
Living? A JAGES Prospective Cohort
Study. International Journal ofEnvironmental Research and Public
Health,16(5):828(2019).
34. Sakamoto A, Ukawa S, Okada
E, et al. : The association betweensocial participation and cognitive
function in community-dwelling older
populations: Japan Gerontological
Evaluation Study at Taisetsu
community Hokkaido. International
Journal of Geriatric Psychiatry,
32(10):1131-1140(2017).
35. Tsuji T, Kanamori S, Miyaguni
Y, et al. : Community-Level Sports
Group Participation and the Riskof Cognitive Impairment. Medicine& Science in Sports & Exercise,
51(11):2217-2223(2019).
36. Tsuji T, Miyaguni Y, Kanamori
S, et al. : Community-level Sports
Group Participation and Older
Individuals' Depressive Symptoms.
Medicine & Science in Sports &Exercise, 50(6):1199-1205(2018).

Tomo Takasugi and Katsunori Kondo

survey conducted from 2010 to 2011 in 53 municipalities confirmed a regional
disparity of 2.9 times the rate of elderly people who could not conduct one of
the following: use public transportation, shop for daily necessities, prepare
meals, pay bills, or manage deposits at a bank or post office. Inability to
conduct any of these activities has been associated with higher dementia risk.
The necessity of visualizing regional circumstances using these indicators(using public transportation, shopping, preparing meals, paying bills,
managing savings) and advancing measures including preventative care
was discussed at a symposium held in 2017 at the 21st World Congress of
Epidemiology. Based on that discussion, a study was conducted on the 98,774
people who participated in the 2010 JAGES survey to investigate regional
diagnostic indicators that will be useful when promoting preventative carethrough community developmental efforts. It discovered that only someindicators of social participation among those examined showed a negative
correlation with low risk factors for dementia, such as participation involunteer groups, sports groups, and hobby groups.37 Dementia and depression– which has been identified as a dementia risk factor – are present in 60 per
cent of elderly people who require support or long-term care. A study on thelikelihood of requiring support or long-term care on a regional level identified
14 indicators that describe regions where likelihood for requiring long-termcare is low. The importance of having many forms of social participation(volunteer groups, sports groups, hobby groups) and social support (reception
and provision of emotional and instrumental support) has been reported
multiple times.38
A cross-sectional JAGES study with 338,659 participants in 105 municipalities
nationwide examined the indicator for the correlation between social
participation and the number of people with forgetfulness, a reported
dementia risk factor. It showed that fewer people experienced forgetfulness
the greater the number of people that engaged in any form of social
participation for more than a few times per year (correlation coefficient: r= -0.72, p<0.001) in the municipality, and that there was a disparity of 1.9
times between municipalities. This suggests that it may be appropriate to use
the ratio of people engaged in social participation or the ratio of people who
experience forgetfulness as regional diagnostic indicators to be used when
implementing dementia risk reduction measures at the municipal level.39
A five-year longitudinal study followed 72,718 people who participated in
the JAGES 2010 survey and 84,211 people who participated in the JAGES
2016 survey in 44 municipalities. In municipalities with 10 per cent higher
participation rates in sports groups once or more per week (partial regression
coefficient B = -0.356) or hobby groups once or more per month (B = -0.309),
there was a trend for the overall community depression rates, a dementia risk,
to be 3 per cent lower.40

37. Yamaguchi M, Inoue Y, Shinozaki
T, et al. : Community Social Capitaland Depressive Symptoms Among
Older People in Japan: A Multilevel
Longitudinal Study. Journal of
Epidemiology, 29(10):363-369(2019).
38. 井手一茂, 宮國康弘, 中村恒穂, ほか. :個人および地域レベルにおける要介護リス
ク指標とソーシャルキャピタル指標の関連の違い JAGES2010横断研究. 厚生の指標,
65(4):31-38(2018).

39. 井手一茂, 鄭丞媛, 村山洋史, ほか. :Intervention studies conducted as part of the Taketoyo Project

介護予防のための地域診断指標 文献レ
ビューと6基準を用いた量的指標の評価.
総合リハビリテーション, 46(12):1205-

1216(2018).

Observational studies showing social participation to be effective atpreventing dementia and other forms of cognitive decline in elderly people
have been accumulated. However, without conducting intervention studies,

16 | Dementia prevention in Japan

40. Jeong S, Inoue Y, Kondo K, et al.
: Correlations between Forgetfulness
and Social Participation: Community
Diagnosing Indicators. International
Journal of Environmental
Research and Public Health,16(13):2426(2019).

Tomo Takasugi and Katsunori Kondo

there is no way to know if social participation can be increased throughintervention or if doing so can prevent cognitive decline. In recognition of thisneed, various regional intervention studies have been carried out in Taketoyo
City in Aichi Prefecture. There, places for elderly people to engage in social
participation called “salons” were established at locations that members of theelderly population could commute on foot.
Three salons were opened in 2007 in Taketoyo City, a city whereapproximately one-fourth of the population is elderly. One or two more
locations were opened every year after that, and as of 2019, preparations
are underway to open the 14th salon. Each location is operated by about 20
city-trained community volunteers. Programs are provided at the community
center one to three times per month and each program is attended by anaverage of about 60 elderly people. Ten percent of the city’s elderly population
participate multiple times per year. In addition to physical exercise sessions,the programs also include a variety of activities like seasonal events,
interaction with children, music, lectures on health, and conversation groups.
Videos of these events can be viewed online.
A seven-year longitudinal JAGES study that examined 2,593 people byparticipation status in the salons showed that the risk for requiring long-termcare with the presence of dementia was lowered by 27 per cent for those who
participated four times or more per year (OR = 0.73, 95 per cent CI:0.54–0.99).41 However, the possibility remains that unobservable differences inbackground factors between the participation and non-participation groups
may have influenced this outcome. For example, it is easy to question if thesalons were only effective because healthier people were able to participate
more frequently, thus further improving the health of those who were alreadyhealthy. To remove such doubts, results were analyzed with a techniqueto verify only the effects of salon participation by minimizing the healthcondition bias between the two sub-groups before the salons were established.
Specifically, results were analyzed using an instrumental variable method,which is considered a pseudo-randomized control trial (RCT). The numberof salons located within 350 meters of the homes of participants was usedas the instrumental variable. Compared to people without a salon nearby,
participation rates increased proportionally to the number of salons nearby,
but there were no differences in health conditions between the two subgroups. In other words, this was a pseudo-RCT in which participants wererandomly divided into participants with salons nearby and non-participants
without salons nearby. The endpoint was set as the certification rate forrequiring support or long-term care including for physical decline other thandementia. The results confirmed that the certification rate for requiringsupport or long-term care among the participating sub-group was lowered by
50 per cent (HR = 0.49, 95 per cent CI:0.33-0.72).42
As described above, multiregional comparisons made possible by JAGES
demonstrated that attention must not only be paid to individual-level factors
causing dementia, but also to factors on the community and society level. It has
also been demonstrated that various factors such as the built environment and

17 | Dementia prevention in Japan

41. Watanabe R, Kondo K, Saito
T, et al. : Change in MunicipalityLevel Health-Related Social
Capital and Depressive Symptoms:
Ecological and 5-Year Repeated
Cross-Sectional Study from the
JAGES. International Journal ofEnvironmental Research and Public
Health,16(11):2038(2019).
.
42. Hikichi H, Kondo K, Takeda
T, et al. : Social interaction andcognitive decline: Results of a 7-year
community intervention. Alzheimer's& Dementia, 3(1):23-32(2017).

Tomo Takasugi and Katsunori Kondo

social participation rates affected the differences in community and social levelfactors. It was shown to be possible for a person to lower their dementia risk bymoving to an area with higher exercise group participation rates, even when otherconditions remained unchanged. Namely, this means one condition for Age-Friendly
and Dementia Cities is having ample opportunities for social participation. In
addition, intervention studies showed that it is possible to conduct communitybuilding in a way that encourages social participation. Among the people in such
communities who started to engage in social participation, dementia and the riskof needing long-term care were prevented. In the future, we look forward to efforts
for creating Dementia Friendly and Dementia Preventing Communities by using
regional diagnostic indicators to evaluate the degree to which social participation is
encouraged.

18 | Dementia prevention in Japan

Tomo Takasugi and Katsunori Kondo

The World Dementia Council (WDC) is an international charity. It consistsof senior experts and leaders drawn from research, academia, industry,
governments and NGOs in both high-income and low- and middle-income
countries, including two leaders with a personal dementia diagnosis. The
WDC has an executive team based in London, UK.
worlddementiacouncil.org© 2020 World Dementia Council
UK charity registration number: 1170743
Cover image credit: Masahiko Yamamoto / Asahi Shimbun Social Welfare Organization