Urban residential environments and senior citizens’ longevity in megacity
areas: the importance of walkable green spaces
+ Author Affiliations
1.
Health Promotion/International Health, Division of
Public Health, Graduate School of Tokyo Medical and Dental University, Tokyo,
Japan - Correspondence to:
Professor T Takano, Health Promotion/International Health, Division of
Public Health, Graduate School of Tokyo Medical and Dental University,
Yushima 1–5–45, Bunkyo-ku, Tokyo 113–8519, Japan;
takano.hlth@tmd.ac.jp
- Accepted 15 May 2002
Abstract
Study objectives: To study the association between
greenery filled public areas that are nearby a residence and easy to walk in
and the longevity of senior citizens in a densely populated, developed megacity.
Design: Cohort study.
Methods: The authors analysed the five year survival
of 3144 people born in 1903, 1908, 1913, or 1918 who consented to a follow up
survey from the records of registered Tokyo citizens in relation to baseline
residential environment characteristics in 1992.
Main results: The survival of 2211 and the death of
897 (98.9% follow up) were confirmed. The probability of five year survival of
the senior citizens studied increased in accordance with the space for taking a
stroll near the residence (p<0.01), parks and tree lined streets near the
residence (p<0.05), and their preference to continue to live in their
current community (p<0.01). The principal component analysis from the
baseline residential environment characteristics identified two environment
related factors: the factor of walkable green streets and spaces near the
residence and the factor of a positive attitude to a person’s own community.
After controlling the effects of the residents’ age, sex, marital status, and
socioeconomic status, the factor of walkable green streets and spaces near the
residence showed significant predictive value for the survival of the urban
senior citizens over the following five years (p<0.01).
Conclusions: Living in areas with walkable green
spaces positively influenced the longevity of urban senior citizens independent
of their age, sex, marital status, baseline functional status, and
socioeconomic status. Greenery filled public areas that are nearby and easy to
walk in should be further emphasised in urban planning for the development and
re-development of densely populated areas in a megacity. Close collaboration
should be undertaken among the health, construction, civil engineering,
planning, and other concerned sectors in the context of the healthy urban
policy, so as to promote the health of senior citizens.
It is generally recognised that greenery filled public areas provide
comfortable and pleasant living environments for urban residents.1,2
Comfortableness, feeling comfortable, in relation to physical environments in
densely populated areas has been studied by measuring people’s preferences.3
However, there is a controversy as to whether substantial positive health
outcomes result from living in localities with greenery filled public areas.4
Hence, the tendency has been to regard the provision of greenery filled public
areas merely as a matter of preference.
For convenience, this paper will refer to greenery filled public
areas that are nearby and easy to walk in such as parks and tree lined streets
as “walkable green spaces”.
The health influences of residential environments have not been
investigated adequately.5
It generally has been acknowledged that it is difficult to demonstrate an
association between health outcomes and residential environments because the
health consequences often are not apparent until some years have passed, and
because many other health determinants also affect both the environmental
conditions of residential areas and the health status of residents. However,
there is a growing concern for physical environmental factors in facilitating
or modifying different health behaviours conducive to health.6
Thus, we conducted a longitudinal cohort study to obtain evidence showing the
health consequences of living in a residence that has walkable green spaces
nearby.
It has been reported that in an urban society a wide variety of
physical, social, and economic factors exhibit interrelationships while also
affecting the health of residents.7–10
Therefore, in this cohort study, we considered multiple variables concerning
physical, social, and economic environments, and we analysed independent effect
of walkable green spaces on the longevity of senior citizens.
Health promotion of older people in a megacity has become a prime
concern in an aging society.11–13
It is well known that a sedentary lifestyle is a key risk of premature
morbidity and mortality.14
For older adults, a sedentary lifestyle is a greater risk of reducing their
physical function than that for younger adults.15
Therefore, to facilitate healthy aging, physically active living should be
encouraged by deliberate arrangements. Giving an exercise prescription was
reported as an effective intervention for sedentary patients to facilitate
their physically active living.16,17
To approach a healthy population in general before they become sedentary
patients, we considered there are some appropriate physical environment
conditions conducive to their physically active living and longevity. We were
particularly interested to study whether walkable green spaces provide a
supportive environment that promotes the health of senior citizens in densely
populated urban areas.
Collaboration of the health and urban planning sectors would be more
firmly grounded if there were evidence of the health promoting outcomes of
particular environments that can be realised through urban planning. People’s
preferences regarding a comfortable living environment are subjective and often
are based on intangible factors. In contrast, longevity is an objective measure
that can be directly quantified. Health issues can provide strong, logical
factors to be considered in urban planning decision making. Demonstrable evidence
that living in an area that has walkable green spaces has a positive impact on
longevity would constitute key evidence for policy making and could facilitate
intersectoral collaboration regarding health promoting urban planning.
Thus, the objective of this study was to investigate, through a
cohort study of older people, the association between walkable green spaces
near the residence and the longevity of senior citizens in a densely populated,
developed megacity in order to provide facts for evidence based policy making
and to advance intersectoral collaboration in urban planning so as to promote
the health of senior citizens.
METHODS
Sampling
A representative sample of residents born in 1903, 1908, 1913, or
1918 was selected from resident registration records in two cities in the Tokyo
metropolitan area—one in the east part and the other in the west part—in 1989.
The following sampling rates were applied: 1/2 for people born in 1913 or 1918,
and 1/1 for people born in 1903 or 1908. A total of 7362 people were selected
and asked to participate in a mail follow up survey of their individual
functional status and health. A total of 5924 people consented for this mail
questionnaire follow up survey. In 1992, a subsequent questionnaire survey was
conducted of those who agreed to participate. We asked about their residence’s
environmental conditions, and about their functional status, lifestyles, living
arrangements, and socioeconomic status. A total of 3144 people responded to the
survey by consenting to use their data with their resident registry records in
later years. This population was defined as the 1992 cohort population to be
followed up in 1997.
Baseline assessment
A baseline assessment of the 1992 cohort, which consisted of 1339
men and 1805 women, was completed during April to June 1992. At the 1992
survey, nine items relating to residential environment were asked and all the
responses were recorded. Percentage of responders to the individual
questionnaire items were from 94.2% to 96.9%. The questionnaire were: space
near the residence for taking a stroll, a park, and tree lined streets near the
residence, noise from automobiles and factories near the residence, the level
of crime in the community, hours of sunlight at the residence, existence of a garden
at the residence, whether the residence faced a road with a regular bus
service, active communication among neighbouring residents, and preference to
continue to live in the current community. The amount of monthly living
expenses was asked and its answer was used as an indicator of the socioeconomic
status of participants. Marital status was asked and its answer was used as an
indicator of participants’ living arrangements.
Follow up
Survival of the respondents as of 31 May 1997 were followed up by our
obtaining official residence records from their local governments, based on
each participant’s informed consent thereto.
Analysis
The association between baseline residential-environment
characteristics and the five year survival of the subject senior citizens was
analysed by use of the χ2, and Kruskal-Wallis tests.
Principal component analysis with Varimax rotation was performed to
extract residential-environmental factors from the variables of environmental
characteristics that showed significant univariate statistical associations
with the five year survival of male and/or female subjects, as calculated in
the earlier tests.
Associations between each of the baseline residential-environmental
factors and five year survival were examined by multiple logistic regression
analysis. Independent influences of residential-environment conditions,
represented by factor scores obtained by the earlier analysis, were calculated
after excluding the effects of age, sex, marital status, and socioeconomic
status. To exclude the effects of lower functional status at the baseline in
individual regression models, we examined logistic regression coefficients for
the subjects of any levels of functional status, and those for subjects who did
not need help to get out of bed at the baseline time.
RESULTS
The survival of 2211 and the death of 897 of the 3144 persons in the
1992 cohort population were confirmed five years later, in 1997. The follow up
rate was 98.9%. The five year survival percentage was higher among women
(75.2%) than among men (65.9%). The five year survival percentage decreased as
the baseline age of the subjects increased, being 85.7% among those 73 years of
age in the baseline year and 43.7% among those 88 years of age in the baseline
year.
Table 1 shows five year survival percentages of older people in
relation to the characteristics of their residential environment, sex, and age.
For the male and female subjects in total, the five year survival percentages
were greater for subjects having either a space near their residence for taking
strolls (p<0.01), or parks and tree lined streets near their residence
(p<0.05). These results were observed for each of the age categories. The
five year survival percentage of senior citizens was greater among those who
preferred to continue to live in their current community than among those who
did not express such a preference (p< 0.01); this was observed for each of
the age categories. The five year survival percentage of senior citizens increased
in accordance with the number of hours of sunlight at their residence
(p<0.01); this was also observed for the age categories of 73 and 78 in the
baseline year.
View this table:
Table 1
Five year survival percentages of the older people by
selected characteristics of residential environment
Statistically greater survival rates were observed among male
subjects who were not subject to noise from automobiles and factories near
their residence (p<0.01) or who enjoyed sunlight at their residence
(p<0.05), but such statistically greater survival rates were not observed among
female subjects under the same conditions.
Among female subjects, five year survival percentages were greater
for those who claimed to have active communication with their neighbours
(p<0.05) and among those who preferred to continue to live in their current
community (p<0.01), but such greater survival percentages were not observed
among comparable male subjects.
Table 2 shows the factor loading of the obtained two factors from
the principal component analysis with Varimax rotation of six living environment
variables. The obtained two factors explained 50.0% of the variances of the six
variables entered. The first factor represented “walkable green streets and
spaces near the residence,” and the other represented “a positive attitude
towards one’s own community.” The average of the standardised factor score of
“walkable green streets and spaces near the residence” among men (−0.0471) was
lower than that among women (0.0375) (p<0.05). The average of the
standardised factor score of “a positive attitude to one’s own community” among
men (−0.0707) was lower than that among women (0.0562) (p<0.01).
View this table:
Table 2
Factor loading for selected living environmental factors
Table 3 summarises the results of multiple logistic regression
analysis. It presents odds ratios with 95% confidence intervals and their
significance level for the residential-environment factor of walkable green
streets and spaces, in order to predict the five year survival of older people.
It shows the odds ratios after adjustment for factor score of another
residential-environment factor, age, sex, marital status, and living expenses
for all of the people who were followed up and for people who did not need help
to get out of bed at baseline. A calculation involving only the male subjects
showed that the factor of walkable green streets and spaces near the residence
was a significant predictor of survival in five years (p<0.05), after
excluding the effects of age, marital status, attitude towards one’s own
community, and living expenses.
View this table:
Table 3
Influence of residential environment factor of walkable
green spaces near the residence on five year survival of older people
The following five living environment variables were found to have a
significantly independently impact on five year survival of older people:
younger age, being a female in sex, living with one’s spouse, higher living
expenses, and positive attitude towards one’s own community individually
independently significantly contributed to predicting the five year survival of
older people. These associations were found in the both models with and without
subjects who did not need help to get out of bed at the baseline time.
DISCUSSION
The quality of the physical environments near a residence—observed
as the space for taking a stroll, tree lined streets, the number of hours of
sunlight at the residence, and less noise from automobiles and factories—showed
a positive association with the longevity of senior citizens. The factor of
walkable green streets and spaces near the residence significantly and
positively influenced the five year survival of senior citizens independent of
a person’s age, sex, marital status, attitude toward their own community, and
socioeconomic status. This association between walkable green spaces and
longevity remained after excluding subjects of very low baseline functional
status. These results clearly show that living in an area with walkable green
spaces positively influenced on the longevity of senior citizens.
Five year survival of the subjects was confirmed by examining
resident registration records, which are one of the reliable sources of
official information regarding the life and death of people in Japan.18
The follow up percentage of 98.9% after the five year period was considered
high enough to reflect the entire population. It is considered that the average
five year survival percentage of the baseline group, 71.1%, as compared with
the follow up percentage, was an appropriate proportion for conducting
statistical analysis throughout this study.
It is probable that the availability of space for taking a stroll
positively contributed to longevity. Booth et al19
demonstrated that the availability of space for walking increased the amount of
a senior citizen’s activity. It has also been reported that more active older
people gain a higher functional status and live longer.20
In addition, the positive influence of walking to reduce risk for coronary heart
disease among women was recently indicated.21
The availability of space near your own residence for taking a stroll is
believed to increase the chances of walking outside of the residence, which
helps to maintain a high physical functional status.
The results with the factor of walkable green streets and spaces
that are independent of personal characteristics suggested that the value of
parks and tree lined streets near residences is particularly high in densely
populated urban areas for the senior citizens living there. Tanaka et al22
have demonstrated, by using aggregated data, a positive correlation between
woodland/farmland area and lower mortality rates for residents of cities having
a density of more than 4000 inhabitants per km2, but not among
cities having a sparse population density. An apparent association between
senior citizens’ longevity and walkable green spaces near their residence,
which was observed in the present cohort study, was consistent with our
previous ecological study. The present cohort study was carried out in highly
densely populated urban areas; the average population density of our study
areas was 13 050 inhabitants per km2. The per capita park space in
Tokyo was 5.18 m2 in 1997, and the “greenery rate” as a percentage
of the sum of the areas of forests, grass area, agricultural land, garden
greens, parks, trees along streets, riverside and pondside space was 29% in the
centre area of Tokyo.23 If you consider that most of the Tokyo
metropolitan area is a highly densely populated urban area, the results
obtained in this study can be regarded as important evidence on which urban
planning in Tokyo should be based.
Urbanisation has accelerated the spread of rapid motorisation and
the development of road networks in densely populated urban areas.24
Congested traffic on narrow roads, highly concentrated development, and little
open space for relaxing places are some examples of characteristics about which
we are concerned.25,26
Although all of the measurements of atmospheric sulphur oxides, 85.2% of
measurements of atmospheric nitrogen oxides, and 78.6% of measurements of
suspended particulate matter from general monitoring stations have met the
environmental standard in the urban centre of Tokyo,27
the long term influence of slightly unpreferable air quality on senior citizens
is a matter of concern.28
In such a congested environment, existence of greenery along the streets and
small parks within residential zones is considered to improve air quality and
provide favourable conditions for the living of senior citizens.23
A number of studies have shown that active living helps to maintain and improve
the functional status of older people.29–31
The current situations in urban environments might discourage the elderly from
moving around easily outside of their residence. It is generally acknowledged
that green spaces provide settings for healthy exercise and that they induce
citizens to walk.32 It was reported that community groups are
walking along newly developed walking trails with greenery by a river in the
study area.33 It was considered that living in an area
that provides good access to walkable green spaces facilitates activities
outside a person’s residence. Studies have shown that walkable green spaces in
residential areas contribute to the health of senior citizens, in part by
facilitating their activity outside of their residence.
It has been pointed out that the ability to live in a better
residential environment is associated with higher socioeconomic status.34
It is also known that there is an association between higher income and a lower
risk of mortality.35,36
This study showed a significant association between socioeconomic status and
longevity. However, it is noteworthy that we found a clear and significant
association between walkable green spaces and longevity, even after excluding
the influence of socioeconomic conditions on longevity. Furthermore, after excluding
the influence of a person’s baseline functional status, there still was a
significant association between walkable green spaces and longevity.
Our findings suggested that if favourably walkable green streets and
spaces were provided, the health of senior citizens would be promoted further,
regardless of their socioeconomic status. These results could be generalised in
a densely populated urban centre where senior citizens live in medium rise to
high rise apartment housing complexes without their own gardens or in detached
houses with limited areas for your own garden. The obtained evidence that
walkable green streets and spaces promote the health of senior citizens was
considered to be useful in supporting a decisive shift in the longstanding
urban planning policy debate in favour of the proponents of public policies
that put priority on health. This evidence also strongly supports the
preference of people for comfortable living environments. Vision sharing and
consensus building in the community for city planning would be more
constructive if supported not only by intangible preferences but also by
substantial evidence showing health outcomes.
Key points
·
A five year cohort study showed that residential
environments with walkable green spaces positively influenced the longevity of
urban senior citizens.
·
This association was observed independent of a
person’s age, sex, marital status, baseline functional status, and
socioeconomic status.
·
The obtained evidence is believed to constitute
a basis for a decisive shift in favour of urban planning policy that promotes
the health of residents.
·
The provision of greenery filled public areas
that are nearby and easy to walk in should be advanced by intersectoral
collaboration.
Master plans for urban development should pay more attention to
maintaining and increasing greenery filled public areas that are easy to walk
in and are within easy walking distance of every household. Closer and more
effective collaboration among health, construction, civil engineering, planning,
and other relevant sectors including government agencies, which has been
minimal until now, should be encouraged more, on the basis of the present
evidence.
In conclusion, based on a five year follow up cohort study of 3144
older people in Tokyo, a densely populated megacity, the longevity of senior
citizens is positively influenced by their living in areas with walkable green
spaces, independent of a person’s age, sex, marital status, baseline functional
status, and socioeconomic status. Greenery filled public areas that are near to
residences and easy to walk in should be further emphasised in the development
and redevelopment of densely populated areas in a megacity through
intersectoral collaboration.
Footnotes
·
Funding: this work has been supported by a grant
in aid for scientific research by the Ministry of Education, Japan.
·
Conflicts of interest: none.
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