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7
Physical and Social
Environmental Factors
T
he previous chapters of this report focused on health systems and
individual and household-level risks that might explain the U.S.
health disadvantage, but it has been increasingly recognized that
these health determinants cannot be fully understood (or influenced) in
isolation from the environmental contexts that shape and sustain them.
In contrast with traditional environmental health approaches that focus
primarily on toxic substances in air, water, and soil, this more recent
approach conceptualizes the environment more broadly to encompass a
range of human-made physical and social features that are affected by
public policy (Frumkin, 2005). These economic, social, urban or rural,
transportation, and other policies that affect the environment were not
traditionally thought of as relevant to health policy but are now attracting
greater attention because decision makers are beginning to recognize their
health implications (Cole and Fielding, 2007).
By definition, environmental factors affect large groups that share com-
mon living or working spaces. Thus, they are key candidates as explanatory
factors for health differences across geographic areas, such as countries.
Indeed, a major motivation for the research on environmental determinants
of health has been the repeated observation that many health outcomes
are spatially patterned. These patterns are present across countries and
across regions within countries, as well as at smaller scales, such as across
urban neighborhoods (Center on Human Needs, 2012b; Kawachi and
Subramanian, 2007). Strong spatial variation is present for a large range of
192
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PHYSICAL AND SOCIAL ENVIRONMENTAL FACTORS 193
health outcomes, including many of the outcomes for which there are cross-
national health differences, such as noncommunicable diseases, associated
risk factors, injuries, and violence.
Understanding the reasons for the spatial patterns of health within
countries may shed light on environmental factors that may contribute
to differences across countries. Several factors may explain the strong
spatial patterns that are observed within countries. A key contender is
the spatial sorting of people based on their socioeconomic position, race,
or ethnicity. However, evidence suggests that regional and neighborhood
differences in health persist even after adjusting for these socioeconomic
and demographic factors (Diez Roux and Mair, 2010; Mair et al., 2008;
Paczkowski and Galea, 2010; Pickett and Pearl, 2001). This evidence
suggests that broad environmental factors may play an important role in
health. Moreover, environmental factors linked to space and place may in
turn contribute to and reinforce socioeconomic and racial or ethnic health
disparities (Bleich et al., 2012; Laveist et al., 2011). Thus, individual and
environmental factors may be part of a reinforcing cycle that creates and
perpetuates health differences. These reinforcing processes by which envi-
ronmental factors and individual-, family-, and community-level factors
reinforce each other over time may also play an important role in generat-
ing cross-national differences in health.
This chapter focuses on both the physical and social environment in the
United States as potential contributors to its health disadvantage relative
to other high-income countries. This chapter, like others before it, focuses
on three questions:
• Do environmental factors matter to health?
• Are environmental factors worse in the United States than in other
high-income countries?
• Do environmental factors explain the U.S. health disadvantage?
QUESTION 1: DO ENVIRONMENTAL
FACTORS MATTER TO HEALTH?
Many aspects of the physical and social environment can affect people’s
health.1 Spatial contexts linked to regions or neighborhoods are among
1
Although analytically distinct, physical and social environments may also influence and
reinforce each other: for example, physical features related to walkability may contribute to
social norms regarding walking, which may in turn promote more walkable urban designs
and community planning.
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194 U.S. HEALTH IN INTERNATIONAL PERSPECTIVE
the most frequently studied,2 but other contexts may also be important for
certain segments of the population.3
Physical Environmental Factors
The factors in the physical environment that are important to health
include harmful substances, such as air pollution or proximity to toxic sites
(the focus of classic environmental epidemiology); access to various health-
related resources (e.g., healthy or unhealthy foods, recreational resources,
medical care); and community design and the “built environment” (e.g.,
land use mix, street connectivity, transportation systems).
The environment can affect health through physical exposures, such as
air pollution (OECD, 2012b). A large body of work has documented the
effects of exposure to particulate matter (solid particles and liquid droplets
found in the air) on cardiovascular and respiratory mortality and morbid-
ity (Brook et al., 2010; Laumbach and Kipen, 2012; Mustafic et al., 2012;
´
Tzivian, 2011). Research has identified specific physiologic mechanisms
by which these exposures affect inflammatory, autonomic, and vascular
processes (Brook et al., 2010; Tzivian, 2011).
The effects of particulate matter on mortality appear to be consistent
across countries. For example, a recent review of studies from the late 1990s
to mid-2000s found a consistent inverse relationship between airborne par-
ticulate matter and birth weight in Australia, Brazil, Canada, France, Italy,
the Netherlands, South Korea, the United Kingdom, and the United States
(Parker et al., 2011a). Another notable example is the evidence linking lead
exposures to cognitive development in children (Bellinger, 2008; Levin et
al., 2008). The evidence of environmental effects of air pollution and lead
has been reflected in legislation in many countries directed at reducing levels
of these pollutants in the environment.
Increasing attention has focused on the implications for health behav-
iors and social interactions that are created by the built environment. The
2
Much early work on the spatial patterns of health used variables such as aggregate sum-
maries of area socioeconomic or race/ethnic composition or measures of residential segregation
by various attributes as proxies for a range of broadly defined environmental factors that may
be relevant to health (see, e.g., Diez Roux and Mair, 2010). The identification of causal effects
using these aggregate summaries raises a number of methodological challenges and does not
allow one to identify the specific environmental attributes that may be relevant. More recent
work has attempted to identify the specific environmental factors that may be important to
specific health outcomes, as well as the pathways through which these factors may operate.
3
The environment can also be considered on a larger geographic scale, especially in seeking
explanations for cross-national health differences. For example, the health of some nations is
affected by their geography or climate.
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PHYSICAL AND SOCIAL ENVIRONMENTAL FACTORS 195
built environment refers to the presence of (and proximity to) health-
relevant resources as well as to aspects of the ways in which neighborhoods
are designed and built (including land use patterns, transportation systems,
and urban planning and design features). An important example is evidence
that links proximity to healthy or unhealthy food stores with dietary behav-
iors and related chronic disease outcomes (Babey et al., 2008; Larson et al.,
2009; Moore et al., 2008; Morland et al., 2006).4 Food availability and
food advertising influence energy intake and the nutritional value of foods
consumed (Grier and Kumanyika, 2008; Harris et al., 2009; Institute of
Medicine, 2006a).
Another large body of work has documented how walking and physi-
cal activity levels are affected by access to recreational facilities, land use
mix, transportation systems, and urban planning and design (Auchinloss et
al., 2008; Diez Roux et al., 2001; Ding et al., 2011; Durand et al., 2011;
Gordon-Larsen et al., 2006; Heath, 2009; Kaczynski and Henderson, 2008;
McCormack and Shiell, 2011; Transportation Research Board, 2005).
Studies conducted in the United States and other high-income countries
have found that “walkability” (which is measured by such proxies as build-
ing density, land use mix, and street connectivity) predicts walking patterns
(Durand et al., 2011; Inoue et al., 2009; Sundquist et al., 2011; Van Dyck
et al., 2010). Across countries, studies have also shown that physical activ-
ity by children is associated with features of the built environment, includ-
ing walking-related features, and physical activity resources (Bringolf-Isler
et al., 2010; Davison and Lawson, 2006; Galvez et al., 2010; Sallis and
Glanz, 2006).5
Although more definitive evidence is needed (see Feng et al., 2010), it
has been hypothesized that these environmental features may contribute
to the obesity epidemic (Galvez et al., 2010; Papas et al., 2007; Sallis and
Glanz, 2009). The importance of residential environments to obesity and
related conditions, such as diabetes, was recently highlighted by a random-
ized housing intervention: low-income participants who were randomly
assigned to move into low-poverty areas experienced significant improve-
4
Although in the U.S. context a number of studies have reported associations of local ac-
cess to healthy foods with diet, some studies have not detected such associations (Cummins et
al., 2005; Pearce et al., 2008). An important difficulty in comparing results across countries
is that the proxy measure for the local food environment is often the type of food stores or
restaurants available (such as supermarkets or fast food outlets), but the extent to which these
typologies reflect relevant differences in the foods actually available to consumers may differ
significantly across countries.
5
Studies that compare the effects of built environment features across countries are limited
and inconclusive. One recent review found that access to open space (parks and other green
spaces) in neighborhoods was associated with physical activity levels in both the United States
and Australia (Pearce and Maddison, 2011).
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196 U.S. HEALTH IN INTERNATIONAL PERSPECTIVE
ments in weight and diabetes indicators (Ludwig et al., 2011). Unfortu-
nately, the study was not designed to identify the specific environmental
features responsible for the observed effect.
A range of other physical environmental features have been linked to
other health outcomes. For example, the density of alcohol retail outlets has
been linked to alcohol-related health complications (Campbell et al., 2009;
Popova et al., 2009), including injury and violence (Cunradi et al., 2012;
Toomey et al., 2012). Transportation systems and other aspects of physi-
cal environments that influence driving behaviors are also related to injury
morbidity and mortality (Douglas et al., 2011). Living in socioeconomically
disadvantaged neighborhoods (as a proxy for a range of environmental
exposures) has been linked to higher rates of injury in both adults and
children (Cubbin et al., 2000; Durkin et al., 1994).
Social Environmental Factors
Factors in the social environment that are important to health include
those related to safety, violence, and social disorder in general, and more
specific factors related to the type, quality, and stability of social connec-
tions, including social participation, social cohesion, social capital, and the
collective efficacy of the neighborhood (or work) environment (Ahern and
Galea, 2011).6 Social participation and integration in the immediate social
environment (e.g., school, work, neighborhood) appear to be important to
both mental and physical health (DeSilva et al., 2005). What also seems
important is the stability of social connections, such as the composition and
stability of households7 and the existence of stable and supportive local
social environments or neighborhoods in which to live and work.
A network of social relationships is an important source of support
and appears to be an important influence on health behaviors. Work on
the “transmission” of obesity through social networks has highlighted
the possible importance of social norms in shaping many health-related
behaviors (Christakis and Fowler, 2007; Hruschka et al., 2011; Kawachi
and Berkman, 2000).8 A long tradition of sociological research links these
social features not only to illness, but also to risks of violence (Morenoff
et al., 2001; Sampson et al., 1997). Social environments may also operate
6
Other factors that are also frequently discussed, such as social norms, have been more dif-
ficult to study because of a variety of methodological and data challenges.
7
As noted in Chapter 6, divorces and single-parent households have become more prevalent
in the United States over time than in other high-income countries.
8
Analytical complexities make the isolation of these effects difficult in observational studies.
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PHYSICAL AND SOCIAL ENVIRONMENTAL FACTORS 197
through effects on drug use, which also has consequences for violence and
mental-health-related outcomes.9
Neighborhood conditions can create stress (Cutrona et al., 2006; Do
et al., 2011; Merkin et al., 2009), which have biological consequences (see
Chapter 6). Features of social environments that may operate as stress
ors (including perceptions of safety and social disorder) have been linked
to mental health, as have factors that could buffer the adverse effects of
stress (e.g., social cohesion, social capital) (DeSilva et al., 2005; Mair et
al., 2008).
One mechanism through which the social environment can enhance
health is through social support. Social support has appeared in many
(but not all) studies to buffer the effects of stress (Cohen and Wills, 1985;
Matthews and Gallo, 2011; Ozbay et al., 2007, 2008). Resilience to the
adverse health effects of stress has also been tied to factors that could influ-
ence how one perceives a situation (threat versus challenge) and how one
responds to stressors (Harrell et al., 2011; Hennessy et al., 2009; Matthews
and Gallo, 2011; Ziersch et al., 2011). One theory for the tendency of some
immigrant groups to have better health outcomes than might be expected
on the basis of their incomes and education (see Chapter 6) is the social
support immigrants often provide one another (Matthews et al., 2010).
Social capital refers to “features of social organization, such as trust,
norms, and networks, that can improve the efficiency of society by facili-
tating coordinated actions” (Putnam, 1993, p. 167). Studies have shown
consistent relationships between social capital and self-reported health
status, as well as to some measures of mortality (Barefoot et al., 1998;
Blakeley et al., 2001; Kawachi, 1999; Kawachi et al., 1997; OECD, 2010c;
Schultz et al., 2008; Subramanian et al., 2002). Social capital depends on
the ability of people to form and maintain relationships and networks with
their neighbors. Characteristics of communities that foster distrust among
neighbors, such as neglected properties and criminal activity, can affect
both the cohesiveness of neighbors as well as the frequency of poor health
outcomes (Center on Human Needs, 2012b).
Spatial Distribution of Environmental Factors
In addition to considering differences between the United States and
other countries in the absolute levels of environmental factors, it is also
important to consider how these factors are distributed within countries.
Levels of residential segregation shape environmental differences across
neighborhoods (Reardon and Bischoff, 2011; Subramanian et al., 2005).
9
Although findings have not always been consistent, levels of safety, violence, and other
social environmental features have also been found to be associated with walking and physical
activity (Foster and Giles-Corti, 2008).
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198 U.S. HEALTH IN INTERNATIONAL PERSPECTIVE
Neighborhoods with residents who are mostly low-income or minorities
may be less able to advocate for resources and services. Perceptions and
stereotypes about area reputation, local demand for products and services,
and the purchasing power of residents may also influence the location of
health-relevant resources. Physical environmental threats (such as proximity
to hazardous sites) may be more prevalent in low-income or minority neigh-
borhoods, a concern of the environmental justice movement (Brulle and
Pellow, 2006; Evans and Kantrowitz, 2002; Mohai et al., 2009; Morello-
Frosch et al., 2011). These neighborhoods may also lack the social connec-
tions and political power that can help remedy adverse conditions.
Other Environmental Considerations
The panel focused its attention on the role of local physical and social
environments as potential contributors to the U.S. health disadvantage and
did not systematically examine whether other contexts, such as school or
work environments, differ substantially across high-income countries. Nor
did the panel examine whether neighborhood conditions exert a greater
influence on access to health care in the United States than in peer countries.
However, these conditions are important to health. For example, the school
environments of children, adolescents, and college students can affect diet,
physical activity, and the use of alcohol, tobacco, and other drugs (Katz,
2009; Wechsler and Nelson, 2008). Dietary options on cafeteria menus and
in vending machines, opportunities for physical activity, and health educa-
tion curricula are all important to children’s health.
Workplaces have also long been recognized as important determi-
nants of health and health inequalities, occupational safety, and access to
preventive services (Anderson et al., 2009; Schulte et al., 2011). Physical
working conditions (e.g., exposure to dangerous substances, such as lead,
asbestos, mercury), as well as physical demands (e.g., carrying heavy
loads), human factors, and ergonomic problems can affect the health
and safety of employees. Stressful psychosocial work environments and
“job strain”—which refers to high external demands on a worker with
low levels of control or rewards—have become recognized as prominent
determinants of health and have been linked to self-reported ill health
(Stansfeld et al., 1998), adverse mental health outcomes (Clougherty et
al., 2010; Low et al., 2010; Stansfeld and Candy, 2006), and markers of
chronic disease (Fujishiro et al., 2011). Exposure to job strain exhibits a
strong social gradient, which influences inequalities in the health of work-
ers (Bambra, 2011).10
10
Findings on job strain have not been consistent, raising the question of whether these are
primarily markers of socioeconomic position, which can influence health through other plau-
sible material or psychosocial pathways (Eaker et al., 2004; Greenlund et al., 2010).
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PHYSICAL AND SOCIAL ENVIRONMENTAL FACTORS 199
Although the panel did not undertake a systematic comparison of
workplace conditions in the United States and other countries, it did note
that U.S. employees work substantially longer hours than their counterparts
in many other high-income countries. In 2005, annual hours worked in the
United States were 15 percent higher than the European Union average
(OECD, 2008a). Other working conditions and work-related policies for
U.S. employees often differ from those of workers in peer countries. For
example, U.S. workers have a larger gender gap in earnings, which could
potentially affect the health of women, and U.S. workers spend more time
commuting to work (OECD, 2012g), which decreases cardiorespiratory
fitness (Hoehner et al., 2012). Other important differences in work-related
policies include employment protection and unemployment benefits, as
well as family and sickness leave (see Chapter 8). However, cross-national
comparisons of workplace safety, other occupational health characteristics,
labor market patterns, and work-related policies were beyond the scope of
the panel’s review.
QUESTION 2: ARE ENVIRONMENTAL FACTORS WORSE IN THE
UNITED STATES THAN IN OTHER HIGH-INCOME COUNTRIES?
There is scant literature comparing social and physical environmental
features across countries. Here we provide selected examples of the ways in
which levels or distributions of physical and social environments relevant
to health might differ between the United States and other high-income
countries.
Physical Exposures
Few data are available to make cross-national comparisons of expo-
sure to harmful physical or chemical environmental hazards. There is, for
example, little evidence that air pollution is a more severe problem in the
United States than in other high-income countries (Baldasano et al., 2003;
OECD, 2012a; Parker et al., 2011a).11 Although cross-national compari-
sons of the volume of emissions and carbon production per gross domestic
product show that the United States is a major emitter, this finding does not
provide a basis for comparing the cleanliness or healthfulness of air, water,
or other resources. The heavy reliance on automobile transportation in the
United States is linked to traffic levels, which contribute to air pollution
and its health consequences (Brook et al., 2010; Laumbach and Kipen,
11
Averages could mask important spatial heterogeneity in air pollution, and this heterogene-
ity could have important implications for differences in aggregate health if some populations
are systematically exposed to high levels of pollution.
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200 U.S. HEALTH IN INTERNATIONAL PERSPECTIVE
2012). Data on population exposures to air pollution across countries are
relatively scarce (OECD, 2008b). One available measure is the concentra-
tion of particulate matter less than 10 micrometers in diameter (PM-10):12
in the United States, the concentration of PM-10 levels is 19.4 micrograms
per cubic meter, lower than the OECD average of 22 micrograms per cubic
meter (OECD, 2012a).
An important factor that influences a range of environmental features
relates to patterns of land use and transportation. In general, U.S. resi-
dential environments are highly dominated by Americans’ reliance on pri-
vate automobile transportation. This characteristic has promoted dispersed
automobile-dependent development patterns (Transportation Research
Board, 2009) with consequences for population density, land use mix, and
walkability (Richardson, 2004), all of which may have health implications.
In 2008, the United States had 800 motor vehicles per 1,000 people com-
pared with 526 in the United Kingdom, 521 in Sweden, 598 in France, and
554 in Germany (World Bank, 2012b). Cities in the United States tend to
be less compact and have fewer public transportation and nonmotorized
travel options and longer commuting distances than cities in other high-
income countries (Richardson and Bae, 2004). Many European countries
have strong antisprawl and pro-urban centralization policies that may
contribute to environments that encourage walking and physical activity
as part of daily life (Richardson and Bae, 2004).13
Social Factors
International comparisons of the social environment are complicated by
difficulties in obtaining comparable measures of social environments. For
example, aside from their direct links to injury mortality (see Chapter 1),
violence and drug use may be indirect markers of social environmental
features that affect other health outcomes. As noted in Chapters 1 and 2,
homicide rates in the United States are markedly higher than in other rich
nations. There are fewer data to compare rates of other crimes across coun-
tries. As noted in Chapter 5, certain forms of drug use (which is often linked
to other social environmental features) also appear to be more prevalent in
the United States than in other high-income countries.
Although Chapter 6 documented a long-standing trend of greater pov-
erty and other social problems in the United States than in peer countries,
12
Particulate matter less than 10 micrometers in diameter (PM-10) poses a health concern
because it can accumulate in the respiratory system. In particular, particles that are less than
2.5 micrometers in diameter (“fine” particles) are thought to pose the largest health risks (U.S.
Environmental Protection Agency, 2007).
13
Even in these countries, however, automobile use is rising quickly.
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PHYSICAL AND SOCIAL ENVIRONMENTAL FACTORS 201
evidence is more limited to compare these countries in terms of social
cohesion, social capital, or social participation. For example, OECD data
indicate that the United States has the highest prevalence of “pro-social
behavior,” defined as volunteering time, donating to charities, and helping
strangers (OECD, 2011e). At least one study of cross-national differences
in social capital found that the United States ranked at an intermediate level
compared with other high-income countries in measures of interpersonal
trust; the study also found that the United States ranked higher than many
other countries on indicators of membership in organizations (Schyns and
Koop, 2010). A previous National Research Council (2011) report and a
paper prepared for that study (Banks et al., 2010) did not find much evi-
dence that the United States had unique social networks, social support,
or social integration. However, the focus of that paper was on the social
isolation of individuals rather than on social cohesion or social capital
measured as a group-level construct. Other data indicate that nearly 3
percent of people in the United States report “rarely” or “never” spending
time with friends, colleagues, or others in social settings. This figure is one
of the lowest in the OECD (2012a).
On another measure, OECD data suggest that levels of trust14 are
lower in the United States than the OECD average and than in all peer
countries but Portugal, with Nordic countries showing the highest levels
(OECD, 2011e). According to the World Gallup Poll, people in the United
States are less likely than people in other high-income countries to express
confidence in social institutions, and Americans also have the lowest voting
participation rates of OECD countries.
In an interesting link between physical and social environments,
Putnam (2000) has argued that increasing sprawl could contribute to
declining social capital in the United States because suburban commutes
leave less time for social interactions. However, it remains unclear whether
sprawl helps explain differences in levels of social capital, or health, across
countries.
Spatial Distribution of Environmental Factors
Research in the 1990s demonstrated that people of low socioeco-
nomic status were more likely to experience residential segregation in
the United States than in some European countries (Sellers, 1999). More
14
Trust data are based on the question: “Generally speaking would you say that most
people can be trusted or that you need to be very careful in dealing with people?” Data come
from two different surveys: the European Social Survey (2008 wave 4) for OECD European
countries and the International Social Survey Programme (2007 wave) for non-OECD Europe
(OECD, 2011e).
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202 U.S. HEALTH IN INTERNATIONAL PERSPECTIVE
recent evidence also suggests that residential segregation by income and
neighborhood disadvantage has been increasing over time in the United
States (Reardon and Bischoff, 2011). Given the established correlation
between neighborhood, race, and socioeconomic composition and various
health-related neighborhood resources in the United States, this greater
segregation could also result in greater exposure of some population sec-
tors to harmful environments (Lovasi et al., 2009). Although studies of
residential segregation do not directly assess environmental factors, to
the extent that segregation is related to differences in exposure to envi-
ronmental factors, countries with greater segregation may also experience
greater spatial inequities in the distribution of environmental factors,
resulting in greater health inequalities and possible consequences for over-
all health status. Studies that use measures of area socioeconomic char-
acteristics as proxies for environmental features have generally reported
similar associations of area features with health in both the United States
and other countries (van Lenthe et al., 2005), but there is some evidence
that area effects may be greater in countries, like the United States,
which have relatively greater residential segregation (Moore et al., 2008;
Stafford et al., 2004).
At least two studies have suggested that spatial variation in health-
related resources may have very different distributions in the United States
than in other countries. A review of spatial variability in access to healthy
foods found that food deserts—areas with limited proximity to stores that
sell healthy foods—were more prevalent in the United States than in other
high-income countries (Beaulac et al., 2009). A New Zealand study found
that area deprivation was not always consistently associated with lack of
community resources (including recreational amenities, shopping, educa-
tional and health facilities) (Pearce et al., 2007). This finding is in sharp
contrast to studies of the United States, which have found associations
between neighborhood socioeconomic disadvantage and the absence of
resources that are important to public health (Diez Roux and Mair, 2010).
Large geographic disparities in toxic exposures to environmental haz-
ards and in healthy food access have been repeatedly noted in U.S. commu-
nities (Diez Roux and Mair, 2010; Mohai et al., 2009; Pastor et al., 2005).
Similar geographic disparities may exist for other environmental features.
For example, the distribution of walkable environments may be more vari-
able in the United States than in other countries, creating “unwalkable”
islands, where walking is not a viable transportation alternative to driving.
These barriers may inhibit physical activity for parts of the population,
resulting in worse overall health. Levels of safety and violence may also be
more strongly spatially segregated in the United States than in other coun-
tries, resulting in areas with greater exposure to violence and its harmful
health consequences.
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PHYSICAL AND SOCIAL ENVIRONMENTAL FACTORS 203
QUESTION 3: DO ENVIRONMENTAL FACTORS
EXPLAIN THE U.S. HEALTH DISADVANTAGE?
Although no studies have collected the necessary data to determine
directly the contribution of the environment to the U.S. health disadvan-
tage, existing evidence on the health effects of environmental factors and on
differences in levels and distributions of environmental factors between the
United States and other high-income countries suggest that environmental
factors could be important contributors to the U.S. health disadvantage.
Below we review the possible contributions of the environment to major
conditions for which U.S. health disadvantages have been documented.
Obesity, Diabetes, and Cardiovascular Disease
Environmental factors that affect physical activity (primarily through
their effect on active life-styles, including walking) and access to healthy
foods (rather than calorie-dense foods) may help explain differences in
obesity and related conditions between the United States and other high-
income countries. As noted above, land use patterns and transportation
systems differ starkly between the United States and other high-income
countries (Richardson and Bae, 2004; Transportation Research Board,
2009). Transportation behavior also differs between the United States
and other high-income countries, with U.S. residents walking and cycling
substantially less than Europeans (Bassett et al., 2008; Buehler et al.,
2011; Hallal et al., 2012). For example, analyses of comparable travel
surveys show that between 2001-2002 and 2008-2009, the proportion of
“any walking” was stable in the United States, at 18.5 percent, while it
increased in Germany from 36.5 to 42.3 percent. The proportion of “any
cycling” was extremely low and stable in the United States, at 1.8 percent,
while it increased in Germany from 12.1 to 14.1 percent. There was also
less variation in active travel among socioeconomic groups in Germany
than in the United States (Buehler et al., 2011). Although the precise
effects of these transportation differences on people’s energy expenditure
is difficult to quantify, it seems reasonable to expect that different trans-
portation patterns would have important implications for U.S. levels of
obesity (Pucher et al., 2010a).
The food intake of the U.S. population is influenced by both supply
and demand, particularly food availability, advertising, and other aspects
of the way in which meals are socially produced, distributed, and consumed
(including mass production and marketing of cheap calorie-dense foods and
large portion sizes) (Institute of Medicine, 2006a; Nestle, 2002; Story et
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204 U.S. HEALTH IN INTERNATIONAL PERSPECTIVE
al., 2008).15 In addition, there is evidence that food access is more inequi-
tably distributed in the United States than in other high-income countries
(Beaulac et al., 2009; Franco et al., 2008; Moore and Diez Roux, 2006),
which may create problems of food access for vulnerable populations.
Importantly, these various features of the physical environment may
act synergistically, reinforcing their effects and creating an “obesogenic”
environment that affects all U.S. residents, at least to some extent. In addi-
tion, these environmental effects may contribute to the development of
social norms regarding behaviors and weight (Christakis and Fowler, 2007),
which then reinforce certain features of the physical environment, making
them increasingly difficult to modify. This reinforcement creates a vicious
cycle in which the environment contributes to the development of social
norms (such as reliance of automobile transportation) and the behavior
resulting from the norm reinforces the environmental features (such as
absence of bicycle lanes or public transportation) that sustain it.
Injuries
The dominant land use and development pattern espoused in the United
States for decades (Richardson and Bae, 2004) has created dependence
on private automobile transportation, with important implications for
traffic volume and associated traffic injuries and fatalities (Transporta-
tion Research Board, 2009). Once established, the land use patterns and
transportation systems are self-reinforcing and may in turn hinder the
development of efficient and inexpensive public transportation alternatives.
A physical environment that promotes and incentivizes automobile trans-
portation also reinforces social norms regarding travel, which complicates
efforts to modify the patterns. The existing land use patterns and reliance
on private automobile transportation not only contribute to traffic volume
and injury fatalities, but probably also contribute to physical inactivity, air
pollution, and carbon emissions. In this way, a common physical environ-
mental feature may explain the coexistence of the U.S. health disadvantage
on apparently unrelated health domains (obesity and injuries).
Homicides, Violence, Drug-Related Deaths, and HIV Risk
Environmental factors, broadly defined, may also contribute to at least
part of the U.S. health disadvantage in homicide, violence, and drug-related
deaths. As noted above, residential segregation by income in the United
States is associated with violence and related outcomes (Sampson et al.,
15
Advertising also plays an important role in promoting alcohol and tobacco use (Chuang
et al., 2005; Kwate and Meyer, 2009; Mosher, 2011; Primack et al., 2007).
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PHYSICAL AND SOCIAL ENVIRONMENTAL FACTORS 205
1997; U.S. Department of Justice, 2007). Residential segregation by income
and race have also been linked to drug use (Cooper et al., 2007) and HIV/
AIDS risk (Poundstone et al., 2004), other contributors to the U.S. health
disadvantage. Neighborhood violent crime has in turn been linked to low
birth weight (Morenoff, 2003) and childhood asthma (Wright, 2006), two
other health conditions that appear to be more common in the United States
than in other high-income countries. Residential segregation (and its many
social and physical correlates) may be another environmental factor that
affects multiple, seemingly unrelated health domains in which the United
States has a health disadvantage.
Another important environmental influence on homicide and suicide
rates is the ease of access to firearms, which has a strong association with
homicide rates (Hepburn and Hemenway, 2004). Legislative policies in
other countries limit circulation and ownership of firearms by civilians. As
stated in a thorough review by Hepburn and Hemenway (2004, p. 429):
High-income countries outside the United States have much lower rates of
handgun ownership than the United States, and the licensing, registration,
and safe storage regulations they have make it much harder for known
criminals to obtain firearms. Thus, relatively few of the homicides in these
countries are firearm homicides.
CONCLUSIONS
There is some evidence that environmental factors that could affect
the U.S. health disadvantage are worse or are more inequitably distributed
in the United States than in other high-income countries. It is plausible to
hypothesize that factors in the built environment related to low-density land
development and high reliance on automobile transportation; environmen-
tal factors related to the wide availability, distribution, and marketing of
unhealthy foods; and residential segregation by income and race (with its
social and economic correlates) may be important contributors to the U.S.
health disadvantage in many domains.
It is noteworthy that these environmental factors may interact with
other factors at both “higher” levels of broad social policy and “lower” lev-
els that operate at the individual level. For example, high levels of residential
segregation may create large social inequalities across neighborhoods that,
in the presence of easy access to guns, may result in high gun violence and
homicide rates. Easy access to unhealthy foods may interact with personal
sources of stress (e.g., from work) in promoting the consumption of calorie-
dense foods. Environments that discourage physical activity may also limit
social interactions, with potential implications for violence and drug use.
Environments also help to create and reinforce social norms (Hruschka
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206 U.S. HEALTH IN INTERNATIONAL PERSPECTIVE
et al., 2011) that influence health outcomes. In this way, environmental fac-
tors are undoubtedly part of a self-perpetuating cycle that operates across
multiple domains, but delineating exactly how this occurs—and how this
may differ across place and time—will require further research.
Many of the environmental factors relevant to health are directly ame-
nable to policy. Therefore, identifying which of these factors are important
contributors to the U.S. health disadvantage could point to policy inter-
ventions that might reduce the disadvantage. For example, cross-national
comparisons show that levels of active transportation, such as walking or
cycling, can be effectively modified by specific land use and transportation
policies (Pucher and Dijkstra, 2003; Pucher et al., 2010b). Although many
of the data reviewed in this chapter are highly suggestive of an important
role for environmental factors, more empirical evidence is needed to draw
definitive conclusions. Important areas for future cross-national research on
environmental factors and health include (1) characterizing levels and dis-
tributions of environmental risk factors using comparable measures across
countries; (2) documenting inequalities in the distribution of these envi-
ronmental factors; (3) identifying the extent to which these environmental
factors affect health and the extent to which their effects are modulated by
individual-, community-, or country-level factors; (4) examining directly
the contribution of environmental factors to health differences between the
United States and other high-income countries; and (5) studying national,
regional, and local country policies that may curb levels of adverse envi-
ronmental exposures, reduce the extent to which they are inequitably dis-
tributed, or buffer their effects.
The contribution of environmental factors to the U.S. health disadvan-
tage is likely to result from dynamic and reinforcing relationships between
environmental and individual-level factors. Environmental factors also
operate over a person’s life course, so that the environments one experi-
ences early in life may influence health trajectories over time. Environmen-
tal factors are in turn linked to upstream social and policy determinants.
In many ways, the environment can be thought of as the mid- or “meso-”
level of influence linking macrolevel factors (e.g., economic and social
policy) and microlevel processes (e.g., individual behavior). A comprehen-
sive understanding of the causes of the U.S. health disadvantage will require
recognizing how the environment interacts with these other factors and
helps perpetuate or mitigate the disadvantage across a broad set of health
domains.
