Significance Coronary heart disease (CHD) is a major cause of death and disability around the world. While mortality due to CHD in developed countries is steadily declining, CHD still causes about one-third of deaths in persons older than thirty-five years old, making it the leading cause of death in the United States (Sanchis-Gomar et al., 2016). In the United States alone, the American Heart Association (AHA) reported 15.5 million people having CHD in 2016. Nearly half of middle-aged men and one-third of middle-aged women in the USA will develop some form of CHD. The AHA reported that the overall death rate from CHD is 102.6 per 100,000 people (Lloyd-Jones et al., 2010). Mortality from CHD is expected to rise in developing countries due to increased risky behaviors (Sanchis-Gomar et al., 2016). Due to the high prevalence and harrowing death rate, CHD is an important public health issue.CHD is a heavily discussed public health issue mainly because it is a chronic condition and entirely preventable. While factors such as older age and family history of early CHD are not preventable, risky behaviors such as smoking, being physically inactive, and having an unhealthy diet are. We have seen that slight changes in these behaviors account for a significant reduction in CHD mortality in the USA (Maruthur et al., 2009). In 2011, the World Health Organization (WHO) observed decreases in CHD mortality by 63% and 60% in men and women in the USA, respectively between the 1960’s and 1990’s. A large part of this effect was from changes in behavior; decrease in physical inactivity by 5%, smoking by 12%, and total cholesterol by 24% are in part to blame for the fall of CHD mortality. This condition is part of a growing problem of chronic illness that is becoming more prevalent due to rapid globalization, urbanization, and an aging demographic (Sanchis-Gomar et al., 2016). Public health professionals are currently working to address this epidemiological shift, mainly on a prevention level. Previous data shows that some behavioral changes are able to address this problem, so as such we are proposing an intervention for one of these risky behaviors in this paper. For this paper, it is important to differentiate amongst the different heart conditions in the discussions surrounding chronic illness. Coronary heart disease (CHD) falls into a group of cardiovascular diseases. Most mortality due to heart disease is from CHD (Sanchis-Gomar et al., 2016). CHD results from coronary artery disease (CAD), which is characterized by atherosclerosis, a buildup of fat, cholesterol, and other substances in the coronary arteries. CAD can be asymptomatic, but CHD includes diagnoses of angina pectoris, silent myocardial ischemia, and myocardial infarction (Cervellin et al., 2014). In the discussions surrounding CHD, CAD is often used interchangeably due to blurred lines between classifying and diagnosing both conditions and a need for developing more sensitive assays (Sanchis-Gomar et al., 2016). CHD is also included in discussions surrounding heart disease mortality. For the purposes of this paper, we will include CAD and other general heart disease in our discussion of CHD. It is well known that unhealthy diet is a major risk factor for CHD and other cardiovascular diseases. Traditionally, low density lipoprotein (LDL) cholesterol levels are measured as a biomarker for CHD (Mente et al., 2009). Some studies have shown that high LDL levels are associated with high glycemic load diets, which are loaded with processed added sugar (Mathews et al., 2015). Therefore, in order to reduce risk of CHD, the intervention should encourage people to eat more complex carbohydrates, lower overall fat intake, and consume more fruits and vegetables. This intervention will specifically focus on increasing fruit and vegetable consumption in a target population already at higher risk for CHD.The target population for this intervention are adults from ages 45 years old to over 65 years old living in Pierce County, Washington, USA. Pierce County is the second most populated county in Washington state. Heart disease is the second leading cause of death in Washington state due to the rates of mortality from CHD (“Mortality and Life Expectancy,” 2015). In Pierce County, heart disease is the leading cause of death, with a rate of 226.7 per 100,000 compared to Washington State’s 196.8 per 100,000 (“Coronary Heart Disease,” 2015). Compared to Washington State, Pierce County has a relatively young population with those being under the age of 18 years old making up 24.9% of the population. This is compared to individuals over the age of 65 years old making up only 11% of the population. However, we expect the demography of this region to change as the Baby Boomers (born 1946 to 1964) continue to age and bring about more demand to the healthcare sector for management of chronic illness. Pierce County already has a higher age-adjusted death rate than the state rate (“Mortality and Life Expectancy,” 2015). From this information about Pierce County, we can conclude that there is a great need for interventions to prevent heart disease, especially before the Baby Boomers turn 65 years old. In 2013, the Community Health Status Assessment conducted a survey asking residents in Pierce County to identify what they thought were major concerns for the health of their community. One of the major concerns was the lack of access to and affordability of nutritious food (“Pierce County COMMUNITY HEALTH STATUS ASSESSMENT,” 2013). People in the region live either far away from a grocery or convenience store, or even far away from a bus stop. This puts lower income people at risk, and Pierce County already has a low average household income compared to the State. Thus, an intervention focusing on improving diet should implement affordable and sustainable healthy food sources along with changing behavior. Previous studies have shown that there is an association between participating in community gardens and fruit and vegetable consumption in adults. One study showed that those who reported participated in a community garden were more likely to eat fruits two or more times a day, along with vegetables three or more times a day than those who did not participate in community gardens (Barnidge et al., 2013). Pierce County already has over 70 working community gardens (“Community Gardens of Pierce County,” 2017). These community gardens coupled with the fact that, according to the 2013 State Indicator Report on Fruits and Vegetables, Washington State itself is good for growing crops and has no shortage, makes for a good intervention implementing usage of community gardens. This intervention will focus on improving the diets of the target population by implementing support groups and participation in self-sufficient community gardens. There are several objectives to this intervention that follow an immediate, intermediate, and long term track. Overall, this is a 3 year program with a 2 year follow-up. Specifically within this population we will target those who have already reported high LDL cholesterol levels. Initially, there are two immediate objectives. The first immediate objective is to improve knowledge about cardiovascular disease and risks of CHD in the community. According to previous studies, the public’s general knowledge of cardiovascular disease is lacking (Thomas et al., 2009; Wartak et al., 2011). Among underserved populations like the ones in Pierce County, previous studies examining this knowledge base indicate an even lower perception of risk and cardiovascular knowledge (Homko et al., 2008). This puts a population already at high risk of CHD at even greater risk, indicating the need for education first in the process of persuading people to change. We will quantify a greater knowledge base of cardiovascular disease by administering quizzes before and after a community seminar, along with measuring an increase in the number of questions answered correctly about CHD. The second immediate objective, that will be attained both concurrently with the first immediate objective and after, is to build support networks. These support networks will be discussed further in the theoretical approach section of this paper, and they will be quantified too by intermittent surveys throughout the 3-year span.The intermediate objective is behavioral. Our goal is to increase fruit and vegetable consumption in the target population by 30% over 3 years. Individuals will keep track in a given journal or phone app of how often they eat fresh produce, where they are getting the produce, etc. The long term objective is what is known as our health objective, which is to reduce incidence of and mortality due to coronary heart disease by 15% over 5 years. We will quantify this by administering a follow up survey two years after the initial 3 year program asking people about any improvements according to doctor’s visits and general health overall compared to when they first started. All surveys used in this intervention will be specific, asking individuals about any elevated cholesterol levels, emergency room visits, heart attacks, etc.Theoretical Approach The Transtheoretical Model (TTM)For this intervention, we are using the Transtheoretical Model (TTM). TTM is good for this intervention in particular in that it evaluates an individual’s readiness to partake in a new health behavior, and provides processes of change to guide said individual. TTM is a model of individual change developed in the 1970s and 1980s by James O. Prochaska, Carlos Di Clemente, and colleagues. It came about from a comparative analysis of twenty-five leading theories of psychotherapy at the time. Originally used to conduct research on smoking, Prochaska and colleagues eventually expanded the stage model to include a variety of health risks, behaviors, and problems (Prochaska et al., 2015). This makes TTM one of the most versatile models for implementing behavior change. TTM has a total of six stages and ten processes of change, and we will be using all of them as described in the next few paragraphs.Precontemplation The education portion of our intervention incorporates the precontemplation stage and all of the processes of change that come with it. Typically, people at this stage do not intend to start the healthy behavior in the near future (within 6 months), and may be unaware that they need to change. The community educational seminars will facilitate a process known as consciousness raising: people here learn more about healthy behavior and are encouraged to think about the pros of changing their behavior and to personally reflect the effects of their negative behavior on themselves and on others. This step is arguably one of the most crucial steps in our intervention; people at the precontemplation stage typically underestimate the pros of changing, overestimate the cons, and often are not aware of making such mistakes. This will then lead them to a process of dramatic relief, where they feel strong emotions about the idea of changing their behavior. They will be encouraged further to become more mindful of their decision making and more conscious of the multiple benefits of changing their unhealthy behavior. This is also the formation of the support group that will help them.ContemplationAt this stage, participants are intending to start participating in the community garden and support group within the next 6 months. In the previous stage, the support system is forming, leading the participants to social liberation. It is crucial that this support group includes both people trying to change and people who have already actively participated in the garden. They see that this behavioral change is socially celebrated by being around like-minded individuals. However, they may still have doubts. While they are usually now more aware of the pros of changing, their cons may be about equal to their pros, causing them to keep putting off taking action. People here learn and reflect on the kind of person they could be if they changed their behavior and learn more from people who behave in healthy ways. Others in the support group can push them further and encourage them to work at reducing their doubts about changing their behavior. They go through the process of self re-evaluation until they go on to the preparation stage.PreparationThe individuals who reach this stage are motivated and ready to start taking action within the next 2 months. They go through a self-liberation: they believe in their ability to change and recommit to it. They begin to take small steps that they believe can help them make the healthy behavior a part of their lives. For example, they tell their friends and family that they want to start going to the community garden more often and bring home produce, adding more support along with the support group at the community garden itself. The individual is then theoretically surrounded by support in all aspects of their daily lives. This is the last stage in completing our first two immediate objectives: the willingness to change and the belief that they have support in this change.ActionThe people then follow through with their community garden participation and support group meetings. They will be encouraged to make community garden participation into an enjoyable past-time and social event. At this stage they go through the processes of counterconditioning (developing a taste for fruits and vegetables rather than processed sugar and fat) and helping relationships (support group meetings). They have changed their behavior within the last 9 months and need to work hard to keep moving ahead as the one year mark passes. The individuals need to learn how to strengthen their commitments to change and to fight urges to slip back. People in this stage progress by being taught techniques for keeping up their commitments, such as substituting activities related to the unhealthy behavior with positive ones, rewarding themselves for taking steps toward changing, and avoiding people and situations that tempt them to behave in unhealthy ways.MaintenanceThe individuals at this stage changed their behavior about 1 year ago. They now go to their community garden, attain produce from the garden, and interact with others of the same goal. This stage leaves room for the next two years of a formal support group and the two years after that to see their results. It is very important for the individuals in these next 4 years to be aware of situations that may tempt them to slip back into doing the unhealthy behavior—especially stressful situations that cause them to crave high fat and high sugar foods more often. “Stress eating” may hinder their progress. The support group keeps each other on track.RelapseRelapse in the TTM specifically applies to individuals who successfully quit smoking or using drugs or alcohol, only to resume these unhealthy behaviors. We are intervening for unhealthy diet. They are encouraged to participate in the processes of stimulus control and reinforcement management. We can also apply this to dietary habits, since previous studies have shown that sugar can be just as addictive as many drugs (Ahmed et al., 2013). The same psychological principles apply. Achieving a long-term behavior change requires ongoing support from family members, a health coach, a physician, the support group, etc. Other resources such as websites and books can also be helpful to avoid relapse. Any relapse should also be met with support so the individual can recover. It may also require reminding the individual of the 2 year follow-up survey to encourage them.Comparison to other theories TTM operates on a few basic assumptions that differentiate it from other theories, and some of these assumptions are very important to the development of our intervention. The first is that theories of health behavior change are different from theories of health behavior themselves. No single theory can account for all theories of behavioral change, hence the development of a transtheoretical approach; this approach integrates many major psychosocial theories (Prochaska et al., 2015). This gives TTM a definite advantage over other theories.We found that a similar heart disease intervention has already been done in Washington State using the Precaution Adoption Process Model (PAPM). This intervention is similar to TTM in that it goes through a process where the individuals are persuaded to change through education and a number of social support strategies are used (Ladd et al., 2009). However, we found that the PAPM intervention seemed to be a bit lacking in terms of the psychological steps taken to induce a behavioral change and a TTM intervention might better address these gaps. In particular, TTM addresses the possibility of relapse, which is important when talking about changing behaviors that mirror addiction. The previous PAPM intervention did not address the possibility of relapse. For future interventions, however, it would also be interesting to design a similar intervention to this from the PAPM approach.DiscussionLimitations TTM is one of the most popular theories for health behavior change. However, it is not immune to criticism. One of the most common criticisms is the supposed discrete nature of the stages; each stage can easily blend into another stage. We found this criticism to be valid in our intervention, since the processes of change tend to blend together amongst two or more stages, i.e. helping relationships. This is necessary in order to form a strong support network, to keep a years-long process. There is also criticism that there is no true benefit to stage-based interventions compared to non-stage-based interventions. However, the evidence for that criticism is conflicting. In 2005, a systematic review of 37 randomized controlled trials claims that there is not enough evidence to claim that stage-based interventions like TTM are more effective in promoting behavior change (Bridle et al., 2005). Conversely, studies that focused on increasing physical activity level showed stage-based interventions having some advantage over non-stage-based interventions (Hemmingsson et al., 2009). Our intervention used all constructs and stages of TTM, but not all studies do. Since many studies do not use all constructs of TTM, additional research suggested that the effectiveness of stage-based interventions increases the more they are tailored to all core constructs and stages of TTM (Friman et al., 2017). This therefore makes our intervention more effective at using TTM. There are also issues with standardizing TTM interventions. For example, in some travel interventions only stages of change and sometimes decisional balance constructs are included (Friman et al., 2017). The processes used to build the intervention use TTM very loosely by classifying participants in a pre-action stage, which blends together the precontemplation, contemplation, and preparation stage, and an action/maintenance stage. This falls into the same previous criticism of TTM decreasing in effectiveness as less of the stages are implemented into the interventions; our intervention does not have that issue of purposely blending stages together or not using some at all, leading us to predict that our intervention can achieve its objectives given we follow through with this plan.Another theory that might have been used in our intervention would be the Health Belief Model (HBM). It was conceptualized in the 1950s and is one of the best known and widely used theories in research and psychosocial change (Rosenstock, 1974). HBM is very similar to TTM. This theory is different in that it does not have discrete stages like TTM. The main feature of this model is that it focuses on the individual’s perceptions of the health behavior and their own abilities to achieve it: this model focuses more on the process of persuading the individual to change and what external factors are causing them to hesitate changing. We believe that using this model in addition to TTM would be beneficial to our target population. Our intervention using TTM relies on the assumption that individuals will be persuaded to adopt these behaviors more readily. As stated before, most people know general terms such as heart disease and stroke, and many people are aware that high cholesterol levels contribute to cardiovascular diseases. But our target population clearly has perceptions that they are helpless and that there are too great of barriers to achieving the behavioral objective. HBM would put more focus into the presence of the community gardens as a way of overcoming perceived barriers. If we were to revise this model, we would most likely include HBM in the process of deciding to change. Then there are problems with our chosen intervention itself. In order for this community to have better health outcomes, there needs to be some level of self-sufficiency (“Pierce County COMMUNITY HEALTH STATUS ASSESSMENT,” 2013). The community gardens are a classic method in promoting self-sufficiency, but there is always the chance that these community gardens might not be sustainable after a few years. The city might cut funding or the people might become disinterested as the nation shifts politics and potential social disarray emerges; there is no guarantee that community gardens and support groups in this population will last. However, building a strong morale in the execution of this intervention greatly decreases the risk of this happening. The use of public spaces for parks and gardens in urban communities has been shown to promote environmental justice and equity, something that the community in the 2013 survey expressed desire for (Ferris et al., 2001). Finally, our results and measuring the effectiveness of this intervention rely heavily on self-reporting. We are addressing that issue by making the surveys as specific and detailed as possible, but even the disease itself and our understanding of the disease is a limiting factor. Throughout this paper we focused on CHD but a lot of our literature review did not make distinctions amongst the different cardiovascular diseases. As discussed earlier, CHD is a result of CAD, but diagnosing between the two diseases is still vague (Sanchis-Gomar et al., 2016). This might also affect our quantifying of our long term health objective if different providers in the area cannot agree on what constitutes CHD from CAD and other cardiovascular disease. Further research is then needed.Conclusions Despite all of these limitations in the theoretical model and reporting strategies, this intervention will contribute to health policy and have a positive impact on the health of this community. This intervention will promote strong social ties. Community gardens promote equity, a factor that is becoming acknowledged more in public health as a determinant of health. If this intervention is successful in lowering rates of CHD in a high risk community like this, this will encourage similar interventions with more community gardens and support groups. Overall, this intervention is part of the movement in public health to promote health on a community level using holistic approaches. Health policy is then moving forward on a positive note.