Abstract
Using the 2024 ranking of causes of death in the Vital Statistics (by sex and 5-year age) and the cause-of-death list for trends for 1950–2024, the youngest age at which senility outnumbers every other cause at that age was followed year by year. It claims no new mathematical theorem and no new law.
First, the tables are consistent. The 2024 senility deaths agree between the ranking table and the trend table (in the 19 cells where senility is in the top 10), and the 2024 answer is the same in both tables (Section 3).
Second, in 2024 senility is first from 90–94 for both sexes and for women, and from 95–99 for men. For men aged 90–94, cancer has 18,822 deaths against 18,661 for senility, so senility ÷ cancer = 0.991 (a difference of 161). For women aged 85–89, cancer has 29,249 against 25,862 for senility. Once first, senility stays first at every older age (Section 4).
Third, this is the core of the paper. The youngest age at which senility is first traced a U shape over the years. For both sexes, it rose from 80–84 in 1950 to 85–89 in 1965, 90–94 in 1970, 95–99 in 1985, and 100+ in 1990–2010, then came down to 95–99 in 2014 and 90–94 in 2021. For women it started at 75–79 in 1950 and came back to 90–94 in 2020. For men, in 1995, 2000, and 2005 senility was not first at any age (Section 5).
Fourth, at the same age, "senility ÷ the largest other cause" at 90–94 fell from 7.11 in 1950 to 0.35 in 2005, approached 1 at 0.99 in 2020, and passed 1 at 1.05 in 2021. In 2024 it is 1.35 (Section 6).
Fifth, the movement of that ratio can be divided into the senility side and the rival's side. At 90–94 from 2005 to 2024, of the change in log of +1.349, the rise in the senility rate accounts for +1.086 (0.80) and the fall in the rival's (heart disease) rate for +0.263 (0.20). From 1950 to 1970, when senility lost first place at 85–89, of −1.306 the senility side is −0.779 (0.60) and the rise in the rival's (cerebrovascular disease) rate −0.528 (0.40), the two working in the same direction (Section 7).
Sixth, what separates them is whether senility moved or the rival competing for first place moved. "From what age is senility the most common cause" is not decided by the amount of senility alone.
Scope note: This paper claims no new mathematical theorem and no new law — the ranking and death counts are in public tables, and this paper only lined them up by year and age. This paper is a structural interpretation of the shape of numbers in public aggregate data; it is not medical advice, not a diagnosis, and not a treatment recommendation. The author is not a physician. Decisions about individual health should be discussed with a physician or a medical institution. This is a preprint that has not been peer reviewed. It does not discuss whether the diagnosis of "senility" is right or wrong. The cause of death is the underlying cause based on death certificates, and this does not blame those who wrote them. Which cause is most common depends on how causes are grouped (cancer is one item combining all sites). The movement over years is the rank among the 15 causes of the trend list, and causes outside it are not compared. Considering that families who cared for someone at the end of life may read it, it is not written as an outlook for any one person's death. About the data: the Vital Statistics (e-Stat) are used under the Government Standard Terms of Use (Version 2.0), and the ratios in this paper were created by processing them. What this paper adds: following the age at which senility is first year by year from 1950 to 2024, showing that it traces a U shape, that it differs by 5 years between the sexes, and that for men there were years when it was not first at any age, and dividing that movement into the senility side and the rival's side.
1. Notation and question
- Age at which senility is first: among the 5-year age groups at 60+, the youngest group in which senility deaths outnumber every other cause at that age.
- Rival: at the same age and year, the cause with the most deaths other than senility.
- Senility ÷ rival: the ratio of deaths at the same age and year (equal to the ratio of rates, since age and year are the same).
- Senility side, rival's side: the change in log (senility ÷ rival) between two years divided into log (ratio of senility rates) and −log (ratio of rival's rates). The two add up to the change in log itself.
Question: How has "from what age is senility the leading cause of death" moved over the years? Did senility move, or did the rival?
Observation 1.1: M020 showed that when adjusted to today's age composition, the leading cause of death becomes senility. M055 showed that the age-specific senility rates traced a U shape with the bottom in 2005. M031 showed that "the most common" changes with how things are grouped. This paper does not adjust for age, and looks at first place age by age.
2. Survey and design
To be honest: the design was decided after seeing the tables.
| Content | |
|---|---|
| Tables | Vital Statistics 2024 (final figures), Volume 1 Table 5.17 (ranking of causes, sex, 5-year age, 2024) and Table 5.15 (cause-of-death list for trends, sex, 5-year age, 1950–2024) |
| Noticed in the survey | Table 5.17 is for 2024 only, so the movement over years is seen in Table 5.15. Of the 16 causes in Table 5.15, traffic accidents are re-listed as part of accidents, so the ranking uses 15 causes |
| How to check | Whether the 2024 answer is the same in the ranking (Table 5.17) and in the rank among 15 causes (Table 5.15) |
| Measures | The youngest age at which senility is first, senility ÷ rival, and the division of the change in log into two parts |
3. Data and checks
Calculation 3.1 The 2 retrieved files were fixed by SHA-256, and the following was checked.
- The title of Table 5.17 is "Volume 1, Deaths, Table 5.17: deaths, death rates (per 100,000 population), and shares by rank of cause, sex, and age (5-year groups)," and that of Table 5.15 is "Volume 1, Deaths, Table 5.15 … deaths and death rates (per 100,000 population)." Table 5.15 has the "総数" (all causes) sheet and 16 cause sheets, and 24 years.
- In each age of Table 5.17, the deaths of ranks 1 to 10 are in descending order. In the 9 groups × 3 (both sexes, men, women) at 60+, the shares of the top 3 agree with deaths ÷ all-cause deaths at that age (Table 5.15) within 0.049 points (within the table's rounding of 0.05 points). At 60+ there are no tied causes listed.
- The 2024 senility deaths agree with Table 5.15 in all 19 cells where senility is in the top 10 of Table 5.17.
- The 2024 "age at which senility is first" is the same in the ranking of Table 5.17 and in the rank among the 15 causes of Table 5.15.
4. 2024: from what age is senility first
Calculation 4.1 Ranking of causes of death in 2024 (Table 5.17, ages 80+)
| Age | First, both sexes | First, men | First, women | Senility share, both sexes |
|---|---|---|---|---|
| 80–84 | Cancer 73,569 | Cancer 44,970 | Cancer 28,599 | 6.9% |
| 85–89 | Cancer 64,697 | Cancer 35,448 | Cancer 29,249 | 12.8% |
| 90–94 | Senility 66,651 | Cancer 18,822 | Senility 47,990 | 21.7% |
| 95–99 | Senility 53,514 | Senility 9,938 | Senility 43,576 | 32.4% |
| 100+ | Senility 19,720 | Senility 2,220 | Senility 17,500 | 47.8% |
Observation 4.2: Senility is first from 90–94 for both sexes and for women, and from 95–99 for men. For men aged 90–94, cancer has 18,822 and senility 18,661, a ratio of 0.991 (a difference of 161). For women aged 85–89, cancer has 29,249 and senility 25,862. At 100+, senility accounts for 47.8% of deaths for both sexes and 49.4% for women. Once first, it stays first at every older age.
5. Core — the age of first place traced a U shape
Calculation 5.1 Youngest age at which senility is first (among the 15 causes of Table 5.15, ages 60+)
| Year | Both sexes | Men | Women |
|---|---|---|---|
| 1950 | 80–84 | 80–84 | 75–79 |
| 1955 | 80–84 | 80–84 | 80–84 |
| 1960 | 80–84 | 85–89 | 80–84 |
| 1965 | 85–89 | 85–89 | 85–89 |
| 1970 | 90–94 | 90–94 | 85–89 |
| 1975 | 90–94 | 90–94 | 90–94 |
| 1980 | 90–94 | 95–99 | 90–94 |
| 1985 | 95–99 | 95–99 | 95–99 |
| 1990 | 100+ | 100+ | 100+ |
| 1995 | 100+ | Not first at any age | 100+ |
| 2000 | 100+ | Not first at any age | 100+ |
| 2005 | 100+ | Not first at any age | 100+ |
| 2010 | 100+ | 100+ | 100+ |
| 2014 | 95–99 | 100+ | 95–99 |
| 2015 | 95–99 | 100+ | 95–99 |
| 2016 | 95–99 | 95–99 | 95–99 |
| 2017 | 95–99 | 95–99 | 95–99 |
| 2018 | 95–99 | 95–99 | 95–99 |
| 2019 | 95–99 | 95–99 | 95–99 |
| 2020 | 95–99 | 95–99 | 90–94 |
| 2021 | 90–94 | 95–99 | 90–94 |
| 2022 | 90–94 | 95–99 | 90–94 |
| 2023 | 90–94 | 95–99 | 90–94 |
| 2024 | 90–94 | 95–99 | 90–94 |
Observation 5.2: For both sexes, it kept rising from 80–84 in 1950, reached 100+ in 1990–2010, and then came down to 95–99 in 2014 and 90–94 in 2021. For women, the age of first place was one group (5 years) younger than for men in 14 of the 24 years, the same in 10, and never older (in 3 of the 14 younger years, senility was not first at any age for men). Women started at 75–79 in 1950 and came back to 90–94 in 2020. For men, senility was not first at any age in 1995, 2000, and 2005, and has been first from 95–99 since 2016. In every year and sex, once first, senility stayed first at every older age.
Figure 1: The youngest age at which senility is first (among 15 causes, ages 60+). Navy is both sexes, orange men, and purple women. The top row is "not first at any age."
6. When did senility ÷ rival pass 1
Calculation 6.1 At the same age, senility ÷ the largest other cause (both sexes)
| Year | 85–89 | 90–94 | 95–99 |
|---|---|---|---|
| 1950 | 3.56 | 7.11 | 7.07 |
| 1955 | 3.22 | 6.12 | 11.88 |
| 1960 | 2.12 | 3.90 | 6.92 |
| 1965 | 1.47 | 2.82 | 4.37 |
| 1970 | 0.96 | 1.79 | 2.61 |
| 1975 | 0.57 | 1.20 | 1.56 |
| 1980 | 0.56 | 1.11 | 1.51 |
| 1985 | 0.44 | 0.75 | 1.12 |
| 1990 | 0.28 | 0.51 | 0.72 |
| 1995 | 0.22 | 0.47 | 0.83 |
| 2000 | 0.19 | 0.41 | 0.72 |
| 2005 | 0.16 | 0.35 | 0.63 |
| 2010 | 0.20 | 0.46 | 0.78 |
| 2014 | 0.30 | 0.69 | 1.07 |
| 2015 | 0.32 | 0.75 | 1.18 |
| 2016 | 0.33 | 0.79 | 1.28 |
| 2017 | 0.36 | 0.81 | 1.26 |
| 2018 | 0.38 | 0.84 | 1.30 |
| 2019 | 0.41 | 0.92 | 1.43 |
| 2020 | 0.43 | 0.99 | 1.53 |
| 2021 | 0.47 | 1.05 | 1.59 |
| 2022 | 0.55 | 1.14 | 1.70 |
| 2023 | 0.58 | 1.21 | 1.78 |
| 2024 | 0.63 | 1.35 | 1.96 |
Observation 6.2: At 90–94, senility ÷ rival fell from 7.11 in 1950 to 0.35 in 2005, approached 1 at 0.99 in 2020, and passed 1 at 1.05 in 2021. In 2024 it is 1.35. At 85–89 it fell below 1 at 0.96 in 1970, and from a bottom of 0.16 in 2005 it came back to 0.63 in 2024, not yet reaching 1. The rival changed over time: at 85–89 it was cerebrovascular disease until 1980 and cancer from 2005, and at 90–94 from 2005 onward it is heart disease (excluding hypertensive).
Figure 2: At the same age, senility deaths ÷ deaths from the largest cause other than senility (both sexes; vertical axis logarithmic). Green is 85–89, navy 90–94, and gold 95–99. The dotted line is 1 (above it, senility is first).
7. The senility side or the rival's side
Calculation 7.1 Dividing the change in log (senility ÷ rival) into two parts (rates per 100,000)
| Age and period | Change in log | Senility side | Rival's side | Share of the senility side |
|---|---|---|---|---|
| 85–89, 1950→1970 | −1.306 | −0.779 | −0.528 | 0.60 |
| 90–94, 2005→2024 | +1.349 | +1.086 | +0.263 | 0.80 |
| 85–89, 2005→2024 | +1.373 | +1.279 | +0.094 | 0.93 |
Observation 7.2: From 2005 to 2024, when senility overtook its rival at 90–94, of +1.349 the rise in the senility rate accounts for +1.086 (0.80) and the fall in the heart disease rate for +0.263 (0.20). From 1950 to 1970, when senility lost first place at 85–89, of −1.306 the fall in the senility rate accounts for −0.779 (0.60) and the rise in the cerebrovascular disease rate for −0.528 (0.40), the two working in the same direction. At 85–89 from 2005 to 2024, of +1.373 the senility side is +1.279 (0.93) and the rival's (cancer) side a small +0.094, and the ratio has not yet reached 1 (0.63). A change in first place is not a movement of senility alone; it includes the movement of the rival.
8. Limitations
- Which cause is most common depends on how causes are grouped (M031). Cancer is one item combining all sites, and splitting by site would change the answer. This paper used the published classification as it is.
- The movement over years is the rank among the 15 causes of the trend list, and causes outside it (aspiration pneumonia, dementia, and others) are not compared. For 2024 it was checked that the answer is the same as the ranking table, but not for other years.
- The cause of death is the underlying cause, and whether a death is called senility follows the death certificate. Whether the movement on the senility side is a change in how certificates are written or in how people die cannot be separated (M055).
- Age differences within a 5-year group, prefectures, and facilities are not examined. It is not an outlook for any one person's death.
Conclusion
The age at which senility becomes the leading cause of death rose from 80–84 in 1950 to 100+ in 1990–2010 and came down to 90–94 in 2021. In 2024 it is first from 90–94 for both sexes and women and from 95–99 for men, and for men aged 90–94 it is 161 deaths behind cancer (0.991). Of the movement by which senility overtook heart disease at 90–94, 0.80 came from the senility side and 0.20 from the rival's side.
One thing separates them — whether senility moved or the rival competing for first place moved.
On hearing "from what age senility is the most common," check together which year and which sex the numbers are for, and whether senility increased or other causes decreased.
Data and reproduction
| Data | Vital Statistics 2024 (final figures), Volume 1 Tables 5.17 and 5.15 (Ministry of Health, Labour and Welfare; e-Stat) (retrieved 26 September 2026) |
| Terms of use | e-Stat follows the Government Standard Terms of Use (Version 2.0). The ratios in this paper were created by processing it and are not figures produced by the government |
| Scope | Japan, 1950–2024 |
| Checker | 検算/M056.py (--zu also draws the figures). Every number in the text is taken from 検算/M056_output.txt |
| Raw data | The 2 retrieved files and SOURCES.md in data/ (URLs, retrieval date, SHA-256, terms of use, definitions and how calculations are set up) |
| Figures | 図/M056_zu1, 図/M056_zu2 (png, svg, English versions) |
References
- Ministry of Health, Labour and Welfare. Vital Statistics 2024 (final figures), Volume 1 Tables 5.17 and 5.15 (in Japanese). e-Stat (accessed 26 September 2026). https://www.e-stat.go.jp/
- Yamagishi, Y. (2026). In 1950 the Leading Cause of Death Was Tuberculosis, but Adjusted to Today's Age Structure It Is Old Age, and Tuberculosis Is Fifth [M020]. Zenodo. https://doi.org/10.5281/zenodo.22968057
- Yamagishi, Y. (2026). Which Cancer Is "Most Common" Changes with How Sites Are Grouped — For Both Sexes, the Top Site by Cases Is Colorectum When Grouped, Lung When Colon and Rectum Are Split, and Prostate at ICD Four Characters [M031]. Zenodo. https://doi.org/10.5281/zenodo.22972431
- Yamagishi, Y. (2026). Of the 7.85-Fold Rise in Deaths from Senility from 2005 to 2024, the Age Composition Accounts for 2.51-Fold and the Age-Specific Rates for 3.25-Fold — At Every Age 80+, the Senility Rate Rose 2.66–4.36-Fold While the Sum of Pneumonia, Heart Disease, and Cerebrovascular Disease Rates Fell to 0.50–0.59 [M055]. Zenodo. https://doi.org/10.5281/zenodo.22975275
Reference
Yamagishi, Y. (2026). The Age at Which Senility Becomes the Leading Cause of Death Rose from 80–84 in 1950 to 100+ in 1990–2010 and Came Down to 90–94 in 2021 [M056]. Zenodo.
DOI: 10.5281/zenodo.22975413
YOI: https://www.yamagishiyuuki.com/yoi/M056
ORCID: 0009-0006-8587-3450
PDF (English) · PDF (Japanese) · Date proof of the English PDF (OpenTimestamps .ots) · SHA256SUMS
The record page for this paper (in Japanese, with the PDFs in each language and the date proof): YOI M056. This paper is a preprint and has not been peer reviewed.