Yonago Acta medica 2006;49:93–101

Risk Factors for Death among the Functionally Independent
Elderly Living in Japan: A 3-Year Prospective Cohort Study
Yukiko Haraguchi*†, Yoneatsu Osaki*, Mihoko Mazume‡, Takuji Kishimoto*,
Noriko Yakura† and Mikizo Okamoto**Division of Environmental and Preventive Medicine, Department of Social Medicine, School of
Medicine and †Department of Nursing Care Environment and Mental Health, School of Health
Science, Tottori University Faculty of Medicine, Yonago 683-8503 and ‡Welfare Section, Hoki-cho
689-4133 JapanTo examine risk factors for death in Japanese elderly men and women who live ordinary lives in a community, we performed a prospective cohort study in Kishimoto Town,
Tottori Prefecture, Japan. In September 2001, the town population of the elderly whowere 65 years and older and who lived functionally independently with or without family
was 1383. We delivered questionnaires to them, and collected 1313 (94.9%) answers. Of
the 1313, 29 were highly suggestive to dependent living. Subjects of the baseline survey
consisted of 1284 independent elderly, excluding the 29. The subjects themselves reported
answers to our questionnaire items concerning demographic variables (age, family), history of disease, homebound condition (place of daily activities), activity of daily living(walking, excreting), lifestyle (tobacco), psychology and mental status (subjective health),
quality of life (domestic role) and physical status (body pain, experience of falling). They
were followed-up for 3 years until August 2004. We examined correlations between their
deaths during the follow-up (total number of deaths, 79: 49 men and 30 women) and potential factors for death using the Cox proportional hazard model. By the multivariate
analysis of these variables, we observed that elderly men had four risk factors for death:age (hazard ratio and 95% conﬁdence interval; 1.09 and 1.04–1.14), subjective health (2.45
and 1.40–4.30), domestic role (2.21 and 1.22–4.01) and tobacco (1.96 and 1.10–3.48). Elderly women had two risk factors, age (1.13 and 1.07–1.20) and physical ability or skill in
handling banking duties (one of competence indexes for elderly activities of daily living)(2.45 and 1.12–5.39). Most noticeably, in the present elderly Japanese living functionallyindependently, death was significantly correlated with psychosocial factors (subjective
health, domestic role) rather than physical factors (restriction of going outside due to incontinence).
Key words: community; death; independent elderly; prospective cohort study; risk factor
The average life expectancy for Japanese people
was 78.36 years for men and 85.33 years for women in 2003 (Japan Health and Welfare Statistics
Association, 2004). According to the statistics,
Japanese females have retained the highest aver-age in the world for about 20 successive years.
For both men and women, Japan is one of theremarkable countries for longevity in the world(Japan Health and Welfare Statistics Association,2004). The Japanese life span may have a further

Abbreviations: ADL, activity of daily living; IADL, instrumental ADL; QOL, quality of life: TMIG, Tokyo Metropolitan Institute of Gerontology; WHO, World Health Organization93

Y. Haraguchi et al.

and sometimes interpreted as the same things(Palmore, 2002). Particularly, subjective healthis a reliable indicator of general health for theelderly, reﬂecting both physical health and sociopsychological soundness (Menec et al., 1999).
To our knowledge, workers have rarely investigated risk factors for death in Japanese elderly
living functionally independently in communities.
For the present survey, we deﬁned “independentelderly persons” as those who were not caretakers as approved by the long-term care insurance
system of Japan. At the same time, there were
those who did not mark “dependent” on any offive ADL items at the baseline: walking, eating a meal, excreting, taking a bath and getting
dressed. We utilized several indices based on objective and subjective measures, and studied theirrelationships to death: medical history, physicalfunctions and ability to live an ordinary life were
objectively available, and QOL factors were subjectively evaluated. Our aim was to clarify thephysical and psychosocial risk factors for deaththrough a 3-year prospective cohort study for theelderly men and women independently living in acommunity of Japan.

prolonging tendency in the future, as well. As aresult of their long life, the tendency toward anaged society has progressed more rapidly in Japan
than in other countries. According to the deﬁnition created by the United Nations, when the rateof the 65-year-old or older population (aging rate)
exceeds 7%, the society is aging and when therate exceeds 14%, the society is aged. In othercountries, the length of time that it took for an
aging society to become aged was 115 years forFrance, 85 years for Sweden and 73 years for theUnited States. However, for Japan, the time it
took to reach the “aged” status (from 7% in 1970
to 14% in 1994) was 24 years. In addition, ouraging rate reached 19.5% in 2004, and aging stillgoes on very rapidly. According to recent statistics of the Japanese population, a more than 35%
increase in aging is anticipated in 2050 (Ministryof Health, Labour and Welfare of Japan, 2005).
Until the middle of the twentieth century,
the leading cause of death in Japan was infectious diseases, such as tuberculosis. But after
that, the cause has completely changed into noncommunicable chronic diseases (Japan Health andWelfare Statistics Association, 2004). In studying the vital prognosis of the elderly in developed
countries, we should consider not only the effectsof physical health but also their ability to lead agood life everyday, as well as the effects on their
quality of life (QOL) reﬂecting their satisfactionor happiness. Health was deﬁned in the Constitution of the World Health Organization (WHO)
as a state of complete physical, mental and social
well-being and not merely the absence of diseaseor inﬁrmity (WHO, 1946). The concept or deﬁnition of QOL is still vague and no precise agreement for its deﬁnition has yet been obtained. But
the WHO’s health definition today seems to be
accepted by most researchers as the best so far.
Covering the many research ﬁelds of psychology,sociology or gerontology, the main accepted indicators for estimating QOL are subjective health,subjective well-being (Larson, 1978), pleasure,
life satisfaction and morale (Lawton, 1975).
These are personal subjectivity-based indicators,

Subjects and Methods
Study population
The present prospective cohort study was performed in a community of western Japan, Kishimoto Town (now incorporated into Hoki Town),
Tottori Prefecture. Kishimoto covers an area of
39.09 km 2 , has a population of 7439, with the2071 households (data as of 1 September 2001).
Kishimoto’s population of aged people exceeding
65 years of age was 22.6% in 2001, which was
higher than the national level in 2000, 17.4%. The
number of caretakers approved by town was 249.
The entry criterion for the present study was thenumber of independent residents in Kishimoto asof 1 September, 2001 aged 65 and over. The total
study population at baseline was all 1383 elderly
94

Risk of death among elderly in Japan

residents. From the start of the baseline survey,
this cohort was followed-up between September
2001 and August 2004, 3 years at most. We determined the end point of the study for individual
persons to be the occurrence of death during theperiod. That is, each follow-up period was from
September 2001 to the earliest day of the following 3 years: day of death, day of moving out of
the home or 31 August 2004. All cases of deathand moving out during the period were conﬁrmedby the national local resident registration system.
In September 2001, the questionnaires were
distributed by district welfare commissioners or
members, ﬁlled and sealed by the respondents andcollected by each distributor. Considering the ethics of the baseline survey, the questionnaire wasaccompanied with a written explanation of the
purpose of the survey, strict observance of theirprivacy and a statement of free-will to participate
in the survey. Furthermore, the distributors orally
informed the subjects of the above descriptions
when they distributed the form. We made surethat informed consent was obtained from the subjects when they signed, sealed and delivered theform to their distributors. To conserve personal
information, their names were coded by one of
the authors (MM), the only one who was allowed
to see the subjects’ names, and coded data were
carefully handled only by the other authors. This
study was approved by the Tottori University
Faculty of Medicine Committee for Ethics. The
Kishimoto Town Ofﬁce strictly obeyed the individual information protection enforcement regulations. To the 1383 questionnaires delivered, 1313
elderly replied (answer rate 94.9%). Of those, 29
were “dependent“ in some way according to theﬁve ADL items: walking; taking a meal; excreting; taking a bath; and getting dressed. However,the 29 had not yet applied for the long-term careinsurance system at the town ofﬁce. Because they
were highly likely to live dependently, we excluded them from the survey and the remaining 1284
people were observed as follow-up subjects.

Study items
The study items at baseline generally covered
physical, psychological and social characteristicsof the elderly, which all were reported by subjects
themselves. Firstly, demographic variables wereasked such as gender, age and family constitution.
The study items included three about homeboundconditions: that is, ability of going out (Imuta etal., 1998), frequency of going out (home or out)
(Haga, 2001; Ahiko, 2003). Their instrumental
activities of daily living (IADLs) were evaluated with the TMIG Index of Competence subscales questionnaires which were developed by
the Tokyo Metropolitan Institute of Gerontology(Koyano et al., 1984, 1987). The Index consistedof 13 items classiﬁed under three subscales of instrumental self-maintenance, intellectual activity
and social role. Subjects were asked to answer
yes/no or I can/I cannot. As an index of cognitional function, the presence of forgetfulness was
asked. Quality of life (QOL), psychological andmental status were examined through subjective
health, hobby or pleasure, best friends, reasons forliving, subjective well-being and domestic role.
Subjective health was evaluated by their answer
which they chose from the following four, “excellent, good, fair or poor” to “how would you rateyour health”. Physical status considered to behighly related to death or dependent living was
dysfunction of hearing and visual acuity; falling
experience within the past year; pain in the upperor lower half of the body; restriction on going out
due to incontinence; and degree of chewing force.
History of chronic diseases was asked on sevenclassifications: stroke; heart disease; diabetes
mellitus; fracture or osteoporosis; joint symptom
or rheumatism; Parkinson’s disease; mental disease, psychoneurosis or dementia. Other items
studied were tobacco and community activities.
Statistical analysis
Mortality by gender was analyzed by the chisquare test. The independent variables used were95

Y. Haraguchi et al.

Table 1. Number of deaths in the follow-up subjects during 3 years
Age(year)
65–74
≥ 75
Total

Men
NumberSubjects
Death
239
290
529

15
34
49

P value

Women
NumberSubjects
Death%
Mortality
6.3
11.7
9.3

288
467
755

%
Mortality

2
28
30

0.7
6.0
4.0

< 0.001< 0.006< 0.001

Chi-square test was used to analyze differences between male and female populations.

tory tract disease. Especially in men, death bymalignant neoplasm was more frequent than inwomen. Two men and one woman committed
suicide during the 3 years.

physical, psychological and social variables atbaseline, and the dependent variable was death
which occurred during the follow-up. The variables were analyzed with the Cox proportional
hazard model by sex, and the obtained results
were compared. Firstly, age of the subjects was
adjusted, and each variable was subjected to univariate analysis. Secondly, after adjustment ofage, all variables which showed statistical signiﬁcances by the univariate analysis were used in the
Cox hazard model for the multivariate analysis.
The multivariate analysis produces a probability of multicollinearity. So, when the coefﬁcient of correlation between two variables exceeded 0.5, we adopted 1 variable only for the analysis. Then, we carried out discriminant analysis
using variables which remained in the model after
multivariate analysis. We considered a P value of
0.05 or less to be statistically signiﬁcant for boththe univariate and multivariate analyses. Statistical analysis was performed with SPSS/PC+ statistical software for Windows version 12.0 (SPSS
Japan, Tokyo, Japan).

Univariate analysis
Table 2 shows the univariate analysis of risk factors for death in the elderly during 3 years of follow-up using the Cox proportional hazard model.
Age of the elderly was a signiﬁcant risk factor ofdeath (P < 0.01), as expected. In men, place ofdaily activities (homebound factors) (P < 0.01),
subjective health (psychological and mental status
factors) (P < 0.01), domestic role (QOL factors)(P < 0.01), tobacco (lifestyle factors) (P < 0.05)
and restriction of going out due to incontinence(physical factors) (P < 0.05) were associated withdeath. In women, fewer variables were significantly correlated to death: only two of the TMIG
Index of Competence subscales were correlated.
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Table 1 shows the number of deaths that occurred
during the 3 year follow-up. The number ofdeaths was 79 in total (49 men, 30 women). The
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Fig. 1. Causes of death in the elderly men and womenthat occurred during the follow-up period of 3 years between 2001 and 2004.

96

Risk of death among elderly in Japan

Table 2. Univariate analysis of risk factors for death in the follow-up subjects during 3 years
Risk factor
Category

Dead

Men [529]
Alive
Dead versus alive

Number (%) Number (%) (HR: 95% CI)

Dead

Women [755]Alive
Dead versus alive

Number (%) Number (%)(HR: 95% CI)

Demographic variables
Age (mean ± SD)
78.94 ± 5.89 75.75 ± 5.70 1.08: 1.04–1.13** 83.30 ± 7.82 76.84 ± 5.98 1.16: 1.10–1.22**
Homebound variables
Place of daily activitiesOut
39 (79.6)
452 (94.2) 1.00
24 (80.0)660 (91.0) 1.00
Home
10 (20.4)
28 ( 5.8) 3.34: 1.67–6.71**
6 (20.0)65 ( 9.0) 1.49: 0.59–3.77
TMIG Index of Competence subscales
Self-preparing of mealsCan
33 (67.3)
409 (85.2) 1.00
24 (80.0)671 (92.6) 1.00
Cannot16 (32.7)
7 (14.8) 2.12: 1.14–3.94*
6 (20.0)54 ( 7.4) 0.83: 0.30–2.28
Skill in handling bankingHave
46 (93.9)456 (95.0) 1.00
19 (63.3)
643 (88.7) 1.00
Have not
3 ( 6.1)
24 ( 5.0) 0.93: 0.29–3.02
11 (36.7)
82 (11.3) 2.45: 1.12–5.39*
Newspaper readingDo
46 (93.9)
461 (96.0) 1.00
20 (66.7)
638 (88.0) 1.00
Do not3 ( 6.1)
19 ( 4.0) 1.25: 0.39–4.04
10 (33.3)
87 (12.0) 2.21: 1.01–4.83*
Lifestyle
TobaccoNo smoking
28 (57.1)
339 (70.6) 1.00
28 (93.3)
670 (92.4) 1.00
Smoke
21 (42.9)
141 (29.4) 2.09: 1.17–3.71*
2 ( 6.7)
55 ( 7.6) 0.76: 0.18–3.18
Psychological and mental status
Subjective health
Healthy
25 (51.0)
348 (72.5) 1.00
15 (50.0)517 (71.3) 1.00
Not healthy
24 (49.0)
132 (27.5) 2.47: 1.41–4.32** 15 (50.0)
208 (28.7) 2.03: 0.99–4.16
Quality of life (QOL)
Domestic roleSome
17 (34.7)
283 (59.0) 1.00
20 (66.7)
610 (84.1) 1.00
None
32 (65.3)
197 (41.0) 2.33: 1.29–4.21** 10 (33.3)
115 (15.9) 1.17: 0.51–2.69
Physical status
Going-out restriction due to incontinence
Not limited
42 (85.7)
458 (95.4) 1.00
28 (93.3)
679 (93.7) 1.00
Limited7 (14.3)
22 ( 4.6) 2.49: 1.11–5.61*
2 ( 6.7)
46 ( 6.3) 0.52: 0.12–2.23[ ], population size; CI, conﬁdence interval; HR, hazard ratio; TMIG, Tokyo Metropolitan Institute of Gerontology. HR analysis, based on the Cox proportional hazard model.
Age of the studied population, adjusted.
* P < 0.05.
** P < 0.01.

correlated with death (not listed in Table 2): hazard ratio; 1.74 and 95% conﬁdence interval; 1.04–
2.91.

An independent risk factor for death common toboth sexes was aging (P < 0.01). Men’s signiﬁcant risk factors were subjective health (P < 0.01),
domestic role (P < 0.01) and tobacco (P < 0.05).
Women’s only risk factor was skill in handlingbanking. By using baseline information, the discriminant analysis predicted 67.0% of deaths inmen as expectable from four risk factors of aging,
subjective health, domestic role and tobacco. On

Multivariate analysis
Table 3 shows the multivariate analysis of risk
factors for death in the elderly followed up for 3
years using the Cox proportional hazard model.
97

Y. Haraguchi et al.

Table 3. Multivariate analysis of risk factors fordeath in the follow-up subjects during 3 years
Risk factor
Category

Men [529]
Dead versus alive(HR: 95% CI)

1993; Mongella, 1995). In Sweden, von Strauss
et al. (2003) performed a survey for the elderly,in whom the age was slightly different from ours:
77- to 84-year-old independently living men had ahigher risk of death than age-matched women.
We compared the proportion of causes ofdeath between Kishimoto Town and the wholecountry (Japan Health and Welfare Statistics Association, 2004). Mortality by cerebrovasculardisease was lower and mortality by cardiac or respiratory disease was higher in Kishimoto Town.
This fact seems to result from our conﬁnement ofelderly subjects exceeding 65 years. The suicides
observed in Kishimoto Town were in accordancewith the current national trend (Japan Health andWelfare Statistics Association, 2004).
The univariate and multivariate analyses ofrisk factors for death showed aging, subjective
health, domestic role and tobacco for men. Aging
was the biologically natural sequence. Subjective
health was deﬁned as “the individual’s perception
and evaluation of his or her overall health” (Liang,1986). Many researchers reported it as a predictor of death in the elderly (Mendes de Leon etal., 1996; Mossey and Shapiro, 1982; Tsuji et al.,
1994; Menec et al., 1999; Idler and Benyamini,
1997; Helmer et al., 1999; Kushiro et al., 2003).
These surveys included the dependent elderly tosubjects; however, we excluded the elderly who
had damaged ADL or were living dependently.
To our knowledge, our study is the ﬁrst to prove
the risk of death exactly in functionally independent elderly persons. Smoking is a life habit wellknown as a risk factor for death (Ishii et al., 2000;
Simons et al., 2005). The smoking rate is high inmen, and tobacco exerts serious effects on theirhealth. No domestic role was a significant risk
factor for death in elderly men. In our univariate analysis, their skill in preparing meals forthemselves was a risk only for men. Domestic
work in the Japanese family like housekeeping
are handled by women, while men are much more
involved in social roles. When Japanese men
retire from their job at around 60 years of age,they rapidly lose their role in society and their

Women [755]Dead versus alive(HR: 95% CI)

Aging (per year) 1.09: 1.04–1.14** 1.13: 1.07–1.20**
Subjective health
Healthy
1.00
Not healthy
2.45: 1.40–4.30**
Domestic role
Have
1.00
Have not2.21: 1.22–4.01**
TobaccoNo smoking 1.00
Smoke
1.96: 1.10–3.48*
Skill in handling banking
Have
1.00
Have not2.45: 1.12–5.39*
Discriminant analysis 67.0%

74.2%[ ], population size; CI, conﬁdence interval; HR, hazard ratio.
HR analysis, based on the stepwise Cox proportional
hazard model.
Age of the studied population, adjusted.
* P < 0.05.
** P < 0.01.

the other hand, in women, the analysis predicted
74.2% of deaths as expected from two risk factorsof aging and skill in handling banking. Men’s
sensitivity, specificity and positive predictive
value were 19.8%, 95.3% and 69.6%, respectively.
Women’s sensitivity, speciﬁcity and positive predictive value were 7.3%, 97.2% and 46.7%, respectively.

Discussion
In studying physical and psychosocial risk factors for death in the Japanese countryside, we
observed that men’s mortality during the followup was higher than women’s and slightly higher
than that of younger, 65- to 74-year-old men.
Most developed countries have a sex difference inlife expectancy and death, where women live 5 to
9 years longer than men (Kinsella and Taeuber,
98

Risk of death among elderly in Japan

tors for death (Gilbert et al., 1992) in both sexes.
We observed significant differences in place ofdaily activities and restriction in going out due toincontinence for men by univariate analysis. So,
the tendency to be homebound seemed to be arisk factor for death. Men’s death received moresigniﬁcant effects from psychosocial factors, thanfrom physical factors. According to Pfeiffer (1970)
who studied factors for longevity, the duration ofa human life is regulated compositely by biological, psychological and social factors.
In the present study, men who were aged,
who evaluated badly with subjective health, who
had no domestic role or who smoked at baseline
survey showed a 69.6% probability for deathwithin the following 3 years (the positive predictive value). The value was 46.7% in women who
were aged or who had no skill in handling banking. Particularly, the positive predictive value washigh in men who smoked, bad subjective healthor no domestic role. The impact of these ﬁndings
is very significant in the field of public health.
However, sensitivity was very low in both sexes inthis survey. To increase the validity of screening
it is necessary to prolong the follow-up period.
These risk factors for death can be lowered by theefforts of the elderly themselves, their family or
supporting persons. Men’s early death could be
prevented when good public health measures formen are taken seriously. The tobacco prohibition movement started by the Ministry of Health,Labour and Welfare of Japan in March 2000 has
continued up to the present time. If some factors are improved, the occurrence of death couldat least be postponed. For example, improving
psychosocial risk factors may directly work forprevention of suicide. As observed in younger
generations, quitting tobacco should lead to theprevention of death from tobacco-derived neoplasms and circulatory diseases.
The potential weak point of our survey was
the small number of deaths especially in women
because of the short period of follow-up. This
was the reason for our difﬁculties in ﬁnding statistically significant risk factors. We used theconscience to work falls. Men should have somedomestic role until or after retirement. Domestic
work keeps their ADL or family relations in goodcondition. We studied family structure also as
an independent variable, but both univariate andmultivariate analyses showed no statistical signiﬁcance.
In the elderly women, skill in handlingbanking was the only variable showing a signiﬁcant difference. This lack of signiﬁcant variables
could be attributed to the short follow-up period
and smaller number of deaths, especially in women. Among the women who had died later on,
50.0% and 83.3% gave low answers to subjective
health (hazard ratio and 95% conﬁdence interval;
2.03 and 0.99–4.16) and pain in the lower half ofthe body (2.52 and 0.96–6.61) (P, not signiﬁcantin both). When the elderly cannot handle theirown banking, they might be inclined to be homebound, they might suffer from dementia, or theircompetence in instrumental self-maintenancemight be poor in handling banking. In Japan,
the public pension is automatically transferred toa person’s bank account. According to the 2004
National Life Basics Investigation in Japan, thepublic or national pension income was the only
income in 64.2% of the whole of senior citizen
households (Ministry of Health, Labor and Welfare of Japan Cabinet Secretary Statistics andInformatics Department Social Statistics Division
National Life Basics Investigation Section, 2005).
Additionally, this variable might mean that they
had little money they could use freely, suggesting their financial sparsity. Individual income
and health are correlated (Backlund et al., 1996;
Veenstra, 2003). Effects of income inequality
on women’s subjective health are known (no signiﬁcant difference) (Blakely et al., 2002). Livingwith a low income is a risk factor for death, andthe relationship is marked in very aged women(Veenstra, 2003). We did not ask our subjects towrite the family income, as we were not studying
the effects of this predictor of death.
The present multivariate analysis showedno statistical signiﬁcances in traditional risk fac99

Y. Haraguchi et al.

self-administered method to all items including
physical factors and other objectively measurable indices. This might cause some bias in the
results. Today, individual-based, relative andsubjective assessment draws much attention (Oda,
2003). The answer rate at baseline was as high as
94.9%, and a few subjects moved out of the town
during the follow-up. So, the effects of the above
weak points were minimal. The day of death recorded by the nation-wide local resident registration system was accurate, and we could smoothly
calculate the observation period for each subject.
In addition, the official death certificate form isquite reliable in the aspect of information of mortal disease. In the future in this series of studies,
we will set a longer follow-up period for moredetailed analysis of risk factors, to make predictors of death clearer by classifying age and causesof death. Finally, by investigating how the elderly
become disordered or dependent, we should clarify factors for active-life expectancy.
The present prospective cohort study followed up for 3 years elucidated the predictors ofdeath in functionally independent elderly persons
living in Japan. Psychosocial factors exerted direct effects on death, irrespective of the effects ofphysical factors. This tendency was particularlymarked in men. To lower mortality in independent elderly men and women in a community,
planning better public health programs for improvement of their QOL is eagerly waited.

study on predictors for prevention of dependent living
toward business valuation], from the Ministry of Education, Culture, Sports, Science and Technology of Japan(YO: 15390200).
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Acknowledgments: We are grateful to Professor Yoichi
Kurozawa of the Division of Health Administration andPromotion, Department of Social Medicine, and Professor Soji Fukumoto of the Division of Medical Zoology,
Department of Microbiology and Immunology, Schoolof Medicine, Tottori University Faculty of Medicine, fortheir critical reading of the manuscript. We also thankMs. Yoko Ishikawa of the Division of Environmental
and Preventive Medicine, Department of Social Medicine, School of Medicine, Tottori University Faculty of
Medicine for her cooperation in calculating the collected
information.
This study was supported in part by a Grantin-Aid for Scientiﬁc Research B (2), [An elderly cohort100

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Received October 24, 2006; accepted November 17, 2006
Corresponding author: Yukiko Haraguchi

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