Current healthcare demand models neglect the neighborhood
In order to discuss the role of the neighborhood in healthcare demand prediction models, we will first explain some terminology. We define ‘need’ as the necessity of a person to consume healthcare in order to maintain or restore physical and mental health. Need can be diagnosed by a professional (objective need), observed by the patient (subjective need) or remain unobserved. ‘Demand’ is defined as the objective requirement for healthcare in order to achieve or maintain good physical and mental health. Demand can also occur in the absence of need, such as in the case of preventive care, or without any health-related needs, as in the case of unnecessary care (patient-, or supplier-induced overuse). In addition to overuse, there is also underuse; not everybody who is in ‘need’ is aware of this, and even when the need is recognized, not everybody is willing to demand care. When demand finally leads to action, we talk about ‘healthcare utilization’, or just utilization.
To understand the processes that lead to healthcare utilization, it is necessary to study the mechanisms involved. Andersen’s model of healthcare demand  has been discussed and applied many times in order to explain utilization. This behavioral model, with healthcare utilization as its outcome variable, focuses on the individual behavioral processes that underlie the decision to consume healthcare or not, and hence mainly identifies individual characteristics that influence this decision. The main elements of the model are ‘predisposing factors’ ➔ ‘enabling factors’ ➔ ‘need’ ➔ and ‘utilization’ . The impact of the external environment on health status or the need for healthcare was, however, acknowledged, although only in the third version of the model  and was again omitted from later versions. In the Andersen model, the external environment can affect utilization via two mechanisms. First, the neighborhood can directly affect healthcare utilization at the micro-level through enabling and, second, indirectly via need. Andersen and Newman (, page 16) define enabling as “Enabling conditions make health service resources available to the individual.” The neighborhood may vary in the nature of access to healthcare facilities, in terms of how many facilities are close and/or how easily they can be reached by transportation, for instance. Phillips et al.  worked with Andersen’s model to assess the use of environmental variables in the behavioral model of utilization. They defined the environment as characteristics of the healthcare delivery system, external environment, and community-level enabling factors. They concluded that the lack of environmental variables may have reflected confusion over the model’s conceptualization and that the environmental component may therefore be overlooked by many researchers . Nonetheless, Verheij  applied the Andersen model to explain how the neighborhood affects utilization. He hypothesized that ‘urbanicity’ influences utilization via need, implying that a high degree of urbanization creates more need. These direct and indirect mechanisms are described further in the next section, in which we develop a healthcare utilization model with neighborhood characteristics as a central element and we explain the underlying mechanisms in order to understand the relationship between neighborhood and healthcare utilization.
The neighborhood and healthcare utilization model
Figure 1 shows a simplified representation of the relationship between neighborhood at the meso level and healthcare utilization at the micro level. In this “Neighborhood and healthcare utilization model”, neighborhood characteristics may have positive or negative effects on healthcare utilization. The four arrows from the neighborhood characteristics indicate the mechanisms by which the neighborhood characteristics affect healthcare utilization. From left to right; the neighborhood can affect healthcare utilization via  the supply side,  via need, directly or through mediators, and via  demand for healthcare – irrespective of need. In this model, we will not address the converse influence of healthcare utilization on neighborhood characteristics, in order to keep the model focused.
In the following section, we will explain the elements of the model from meso- to micro-level, starting by defining neighborhood and neighborhood characteristics. We will then explain the mechanisms. The mechanism ‘Via need’ is divided into three subsections because the association of neighborhood characteristics via need to utilization can be explained by three different pathways. In section List of neighborhood characteristics relevant for health care utilization, we will use the dark grey filled boxes (these are the parts that can be operationalized) of the ‘Neighborhood and healthcare utilization model’ to structure the literature overview (Additional files 1 and 2).
Definition of neighborhood and neighborhood characteristics
The idea that the neighborhood affects health is not new. Hippocrates, for instance, ascertained that diseases cluster geographically and he hypothesized that this phenomenon could be explained by ‘the local climate’ . In the late nineteenth century, the physician John Snow came up with environmental explanations for the cholera outbreaks in certain neighborhoods in London. He plotted the cholera infections on a map of London and found an association with the water supply system. With no knowledge of the germ theory of diseases, he was able to identify the channel by which cholera spreads. Despite this, it was not until the end of the twentieth century that the ‘ecological approach’ placed people and their health back into context [18, 19]. The ecological approach in health research implies that human beings are social beings, living their lives in a certain context, not in a laboratory . Moreover, environmental inputs that are relevant to health, such as pollution control, greater public safety, expanded opportunities to improve physical fitness, improved housing or access to education, are beyond the control of any one individual .
Since the emergence of the ecological approach, the neighborhood has been the context of many ecological studies on health outcomes . Early studies focused on the variations in health between neighborhoods. These results widened the focus from individual determinants of health to the apparent impact of the living environment on individual health. The next wave of neighborhood health research studied the health impact of specific neighborhood characteristics. Two broad types of neighborhood characteristics are distinguished: physical and social . Diez Roux and Mair state that the physical neighborhood characteristics include not only “traditional environmental exposures such as air pollution, but also aspects of the man-made built environment including land use and transportation, street design, other features of urban design and public spaces, and access to resources, such as healthy foods and recreational opportunities.” Rollings et al.  go into more detail in their summary of a full list of neighborhood physical attributes that could potentially be relevant to health: “land use, density, street connectivity, transportation availability and infrastructure, pedestrian and cycling infrastructure (presence, condition, and maintenance of sidewalks, bike lanes, cross walks, street lights, traffic lights); access to nature and green space, public and open spaces, and resources (public services, healthcare, healthy food, schools, playgrounds, commercial functions, and recreational opportunities); building and street condition, cleanliness, and maintenance; and traffic volume, air quality, and noise.” In addition to nature and green space, ‘blue space’ has also recently been considered relevant to health . Social neighborhood characteristics include “the degree and nature of social connections between neighbors, the presence of social norms, levels of safety and violence, and various features of the social organization of places” . Hereinafter, we also include socioeconomic aspects of the neighborhood in the social environment of the neighborhood (local prosperity and deprivation), as well as sociocultural aspects like the ethnic composition of a neighborhood community.
In order to understand how these neighborhood characteristics are able to affect healthcare utilization, we describe the mechanisms that may be responsible for a neighborhood effect on utilization, and we underpin these mechanisms with describing the underlying pathways.
As mentioned above, inspired by the Andersen’s model, the neighborhood is hypothesized to have an indirect effect on healthcare utilization via the supply-side (enabling), irrespective of actual need. Kawachi and Berkman  called it the ‘access to services and amenities’ pathway. Neighborhoods can differ in terms of distance, reachability, accessibility, as well as quantitative and qualitative characteristics of healthcare facilities . In the US, people living in disadvantaged neighborhoods, irrespective of their individual-level characteristics, have reduced access to healthcare and were less likely to obtain recommended preventive service [26, 27]. A recent study on disadvantaged neighborhoods in Philadelphia did not reveal this association in relation to overall access, but living in a low-income neighborhood was associated with less reliance on physician’s offices and greater reliance on the safety net provided by health centers and outpatient clinics .
‘Via need’ mechanism
‘Need’ can be operationalized as self-perceived health, well-being, mental health, diseases, and mortality. Neighborhood characteristics ‘get under the skin’  via three different pathways; (1) physiological pathway, (2) psychological pathway, and (3) health behavioral pathway . The first pathway is the direct effect of the neighborhood on health, while the two other pathways operate indirectly via mediators. Even though Berkman et al. formulated these pathways to explain the impact of the social environment on health, we believe that they also apply to the impact of physical neighborhood characteristics.
Physiological pathways between neighborhood and health
The physiological pathway derives from the field of biology and epidemiology and is represented by the arrow that connects neighborhood characteristics directly with need in Fig. 1. This pathway shows a dose response relationship: the stronger and/or longer the exposure to the neighborhood, the greater the effect on an individual’s health. In line with the ‘human basic need theory’ , a neighborhood protects health, because it provides the metabolic requirements for survival, which are basic physiological needs, such as air, water, foodFootnote 1 , shelter and security. Conversely, other physiological effects of the neighborhood can also damage health, such as polluted air, dirty water, nuclear radiation, or noise . One example of a social neighborhood characteristic that has a direct physiological health effect is violent crime: a violent assault may lead to injury. Even when most basic needs are met, as in most Western countries, quality can vary between neighborhoods, leading to health variations between neighborhoods.
Psychological pathway between neighborhood and health
The neighborhood may affect health, on the one hand, through (the experience of) stress and, on the other hand, via the buffering effects of social support and social connections . Chronic stress leads to increased levels of cortisol and other stress hormones, which adversely affects the immune system and increases the blood pressure and other biological risk factors for cardiovascular diseases and cancer . Both physical and social neighborhood characteristics can induce stress. For example, the fear of crime and lack of safety can lead to stress, which negatively impacts mental and physical health . The physical environment, too, such as the quality of the built environment, and the presence of traffic, noise, or a lack of resources, transportation, services, etc. have been linked to depression and other mental health problems .
In addition to inducing stress, physical and social neighborhood characteristics can also have just the opposite effect, helping to mitigate stress . For example, contact with nature (e.g., green space) has short-term restorative effects  and is associated with good perceived mental health . Social support also plays an important role in moderating reactivity in stressful situations . For example, the social support generated in cohesive neighborhoods, particularly emotional support, has been shown to buffer the adverse effects of stressful life events on depression .
Health behavioral pathways between neighborhood and health
The neighborhood may also influence health through its impact on health-related behaviors, because it creates opportunities. Walkable, social, or safe neighborhoods provide more opportunities for physical activity (PA), and PA supports good health  and health-related quality of life . The proximity of sales points for tobacco, alcohol and energy-rich food also influence health behaviors and thus ultimately affect health and healthcare demand among those who live in certain areas .
The neighborhood may also influence health-related behaviors through the presence of social norms and role models. Social cognitive theory states that individuals learn in social contexts; observing a neighborhood ‘model’ may influence individual behavior, and the same applies to the prevailing social norm towards certain behavior . Social capital, defined as sharing common norms, behavioral reciprocity and mutual trust, varies between neighborhoods and has been associated with health-related behaviors, such as PA and smoking . The same study did not support nutrition, sleep habits, or moderate alcohol intake as possible explanations of the effects of neighborhood-based social capital on health. Kawachi et al.  mention three possible pathways by which neighborhood-based social capital may influence health-related behavior: “ promoting more rapid diffusion of health information ,Footnote 2  increasing the likelihood that healthy norms of behavior are adopted, and  exerting social control over deviant health-related behavior” (, page 1190).
Lastly, the neighborhood may influence health-related behaviors through the impact on future prospects. Deprived neighborhoods with high levels of crime and violence can influence the expected costs and benefits of adopting particular behaviors , since people who expect a shorter life-span are less motivated to prevent future health problems through, for example, quitting smoking  or avoiding alcohol abuse .
Healthcare demand mechanism
In addition to the effect of the neighborhood on health, we would like to draw attention to its effect on healthcare demand, irrespective of health, e.g. the demand for stop-smoking programs, even among those who are not suffering from smoking-related disease. The neighborhood may influence willingness to consume healthcare [25, 43]. For instance, the level of social capital, including social norms and values in a neighborhood may motivate people to seek out and use (preventive) healthcare, such as screening for colorectal cancer . In neighborhoods with higher levels of social capital, information may be accessible and spread more easily (, page 1190). Information shared by word-of-mouth is usually taken more seriously and can make the difference in decisions to use healthcare – especially in case of preventive healthcare, thus in the absence of need or health problems. In addition to the information-dissemination pathway, Prentice  suggests that shared neighborhood health-behavior norms may lead to variation in healthcare demand. Another pathway could be ‘practical support from neighbors’ such as a ride to a doctor or taking care of children during medical visits .
List of neighborhood characteristics relevant for health care utilization
To demonstrate the link between neighborhood characteristics and healthcare utilization, we present published scientific literature on neighborhood characteristics in relation to healthcare utilization, as well as to mediators and health outcomes, because need is an important mechanism in explaining the association between neighborhood characteristics and healthcare utilization (Additional files 1 and 2). All the dark grey boxes in Fig. 1 are used to structure Additional files 1 and 2. Additional file 1 shows physical neighborhood characteristics and Additional file 2 shows social neighborhood characteristics. Several studies reported on neighborhood characteristics in relation to healthcare utilization. However, no reviews were available about this association. The empirical evidence is much more detailed and diverse with regard to the association between neighborhood characteristics and health. Mediators of the association of neighborhood characteristics and health were also studied in great number. Additional files 1 and 2 therefore indicate that several neighborhood characteristics are likely to influence utilization; even so the evidence on utilization as a dependent variable is still thin.
Neighborhood characteristics that may influence healthcare utilization are degree of urbanization, public and open space, resources and facilities, green and blue space, environmental noise, air pollution (Additional file 1), social capital, crime and violence, socioeconomic status, stability of the neighborhood, and ethnic composition (Additional file 2). We found as many reviews on physical neighborhood characteristics as social neighborhood characteristics in relation to health. However, the studies on social environmental impacts are much more diverse (e.g. in terms of their definitions, indicators, measurement tools) and therefore do not lead neatly towards one conclusive summary, like reviews on more classical physical environmental hazards, such as the evidence on the impact of the health effects of air pollution.
Even so, most studies are of a cross-sectional nature and the well-known reporting bias that favors the publication of significant study outcomes may have caused an imbalance in our overview, we think that the association between neighborhood characteristics and utilization can be explained very well by combining Fig. 1 with Additional files 1 and 2. For example, neighborhoods with high levels of neighborhood ‘Crime and violence’ may be more likely than other neighborhoods to be perceived negatively by residents. Moreover, these neighborhoods might increasing stress levels and unhealthy behavior and low PA levels. It is therefore likely that neighborhood crime and violence weakens access to healthcare and willingness to demand healthcare, while the actual need to use healthcare may be higher than average.