This page is alzhub.org's plain-English summary of a published study, not the paper itself. It is generated from the record we hold for this study, sourced and linked below — check the original for the full text and methods.

49/100

✓ Peer-reviewed alzhub usefulness score 49 out of 100. How common it is

Reviewed as evidence on: Epilepsy / seizures and young-onset (<65) dementia risk 5 studies (what the news said). Being listed means the study bears on the question, not that it agrees with the news.

Topic: Risk, prevention and care in population studies

The crude prevalence of dementia significantly increased from 1985 to 2012 (6.7% in 1985, 5.7% in 1992, 7.1% in 1998, 12.5% in 2005, and 17.9% in 2012, p for trend < 0.01), but then decreased significantly from 2012 to 2022 (15.8% in 2017 and 12.1% in 2022; p for trend < 0.01). A similar trend was observed after adjusting for age and sex. Moreover, the age- and sex-adjusted incidence of dementia increased significantly from the 1988 to the 2002 cohort (adjusted hazard ratio [aHR] 1.68, 95% confidence intervals [CI] = 1.38-2.06), but decreased significantly from the 2002 to the 2012 cohort (aHR = 0.60, 95% CI = 0.51-0.70). The age- and sex-adjusted 5-year survival rate after dementia onset increased significantly from the 1988 to the 2002 cohort (47.3% to 65.2%; p < 0.01), while no significant change was observed from the 2002 to the 2012 cohort (65.2% to 58.9%; p = 0.42). Decreasing trends in the prevalence and incidence of dementia were observed since 2012 in a Japanese community. The decline in the incidence of dementia may be due to the prevention and improved management of lifestyle-related diseases, such as hypertension and diabetes, as well as increased awareness and promotion of healthy lifestyle behaviors.

Key findings

The crude prevalence of dementia significantly increased from 1985 to 2012 (6.7% in 1985, 5.7% in 1992, 7.1% in 1998, 12.5% in 2005, and 17.9% in 2012, p for trend < 0.01), but then decreased significantly from 2012 to 2022 (15.8% in 2017 and 12.1% in 2022; p for trend < 0.01).
A similar trend was observed after adjusting for age and sex.
Moreover, the age- and sex-adjusted incidence of dementia increased significantly from the 1988 to the 2002 cohort (adjusted hazard ratio [aHR] 1.68, 95% confidence intervals [CI] = 1.38-2.06), but decreased significantly from the 2002 to the 2012 cohort (aHR = 0.60, 95% CI = 0.51-0.70).
The age- and sex-adjusted 5-year survival rate after dementia onset increased significantly from the 1988 to the 2002 cohort (47.3% to 65.2%; p < 0.01), while no significant change was observed from the 2002 to the 2012 cohort (65.2% to 58.9%; p = 0.42).
Decreasing trends in the prevalence and incidence of dementia were observed since 2012 in a Japanese community.

Why it matters

In a Japanese community, dementia prevalence and incidence rose until around 2012 and then declined significantly through 2022, while five-year survival after dementia onset improved from the 1988 to the 2002 cohort but showed no significant change afterward. The authors suggest the decline in incidence may be due to prevention and improved management of lifestyle-related diseases such as hypertension and diabetes.

New to this subject? Start with our plain-English guide: Alzheimer's in numbers →

Study details

Study designcross-sectional
Participants803
Effect size6.7%; 5.7%; 7.1%
Evidence strengthModerate

How this study scored 49/100

Published in a peer-reviewed journal, and it is a snapshot of people at one point in time. Scored zero for randomised / blinded because the record does not state it.

Component	Points	Why
Journal tier	7 / 10	Tier 3 — peer-reviewed journal (Alzheimer s Research & Therapy)
Journal's citation record	1 / 4	Alzheimer s Research & Therapy: journal h-index 146 (OpenAlex, 2026-10-29)
Study design	4 / 12	A snapshot of people at one point in time
Strength of evidence	3 / 5	Rated “moderate” in our summary
Peer-review validation	10 / 10	Peer-reviewed. Published as an article in a named peer-reviewed journal.
How recent	4 / 5	2025 — within 3 year(s) of the newest study here
Sample size	2 / 4	803 participants
Effect reported	2 / 3	Effect reported as a number, without an interval or test
Studied in people	3 / 3	Studied in people (participant count stated)
Randomised / blinded	0 / 2	No randomisation or blinding stated — scores zero (not stated in the record — scored 0)
Times cited	2 / 7	Cited 7 times (OpenAlex, 2026-10-10)
Citations per year	1 / 5	2.3 citations a year over 3 year(s) since 2025
Impact for its field and year	3 / 6	Cited 4.4× the average for papers of its field and year (OpenAlex FWCI)
Cited by studies here	0 / 6	No other study in this library cites it
Still being cited	1 / 4	Cited 7 times in 2024–2026 (2026 still in progress; OpenAlex)
Senior author's track record	1 / 4	Last-listed author Toshiharu Ninomiya: h-index 7 (OpenAlex, whole career)
Institution's track record	1 / 3	Kyushu University: institution h-index 721 (OpenAlex)
Multi-centre collaboration	0 / 3	OpenAlex lists 1 institution(s) in 1 country — scores zero (affiliation lists can be incomplete)
Indexed in PubMed	2 / 2	Indexed in PubMed (PMID 41466306)
Free to read	2 / 2	Free to read
Total	49 / 100	—

What each of these 20 components measures, and what this score is not →

Read the original

Full text: free to read — OpenAlex lists this copy as free to read: the link above (checked 6 Feb 1020).

Cite this study APA, Vancouver, BibTeX · download .bib or .ris

Built from the record alzhub holds for this paper, not looked up. Volume, issue and page numbers are not held in the record. The record's author list ends in “et al.”, so not every author is named. Check the citation against the original before you use it.

APA 7th

Ohara, T., Minohara, T., Nakazawa, T., Oishi, E., Furuta, Y., Sakata, S., et al. (2025). Thirty-seven-year trends in the prevalence, incidence, and prognosis of dementia in a Japanese community: the Hisayama study. Alzheimer s Research & Therapy. https://doi.org/10.1186/s13195-025-01909-1

Vancouver

Ohara T, Minohara T, Nakazawa T, Oishi E, Furuta Y, Sakata S, et al. Thirty-seven-year trends in the prevalence, incidence, and prognosis of dementia in a Japanese community: the Hisayama study. Alzheimer s Research & Therapy. 2025. doi:10.1186/s13195-025-01909-1. PMID: 41466306.

BibTeX

@article{ohara2025-41466306,
  author  = {Ohara, Tomoyuki and Minohara, Toshifumi and Nakazawa, Taro and Oishi, Emi and Furuta, Yoshihiko and Sakata, Satoko and Honda, Takanori and SHIBATA, MAO and others},
  title   = {{Thirty-seven-year trends in the prevalence, incidence, and prognosis of dementia in a Japanese community: the Hisayama study}},
  journal = {Alzheimer s Research \& Therapy},
  year    = {2025},
  doi     = {10.1186/s13195-025-01909-1},
  pmid    = {41466306},
  url     = {https://doi.org/10.1186/s13195-025-01909-1}
}

Studies this one cites

Referenced by this study and also in the alzhub library, so you can read them here.

Related studies in How common it is

Also tagged “epilepsy-and-young-onset-dementia”

5 studies in the library carry the topic tag “epilepsy-and-young-onset-dementia”; these are this study's neighbours in a fixed, alphabetical-by-hash tour of them, not the closest in content. All 5 tagged studies.

Similar studies

More on How common it is

See all studies in How common it is →