The focus of healthcare in a precision healthcare continuum is wellness - an optimal state of health; which acts as a core tenet in catalyzing healthcare's shift from volume-based to value-based care.
The two central components of the P5H continuum consist of Health Stage and Intervention Level, with the primary objective of optimizing patient wellbeing or wellness.
The P5H framework focuses on promoting wellness, detecting and reversing disease transitions, and maintaining an optimal state of wellness.
Within the P5H framework, one can understand a person's state of health through the allostasis and allostatic load models. Allostasis refers to the ability to achieve equilibrium through the change of stress-specific stimuli, essentially referring to the process of adapting to daily experiences and achieving homeostasis through change.
Through the allostasis model, the chronic disease pathway and transition from states of health to chronic disease can be divided into four categories.
Allostatic load and overload are changes in the mind and body that occur when experiencing harmful stress that can cause dysfunction and dysregulation of mediators that usually promote homeostasis, ultimately leading to disease. Adverse health behaviors such as a sedentary lifestyle and smoking contribute to allostatic load and overload.
Despite advancements in modern medicine, many individuals who exhibit symptoms will transition to a confirmed chronic disease diagnosis. Once Stage D has been reached and a chronic disease diagnosis confirmed, there is usually some degree of permanent physiologic damage or dysfunction. For example, a heart attack, stroke, cancer or other long-term diseases will leave permanent damage and dysfunctions that typically require lifelong treatment and self-management. However, this is not true of all conditions, such as type 2 diabetes, which have been successfully reversed or placed into remission after significant long-term dysfunction.
Stage A refers to a healthy individual exhibiting healthy lifestyle characteristics such as regular physical activity, no smoking, a nutritious diet, no alcohol misuse and possessing key health biomarkers such as blood glucose, blood pressure, and blood lipids within normal range. As molecular assessments become available for a broader population, the definition and characterization of apparent health in stage A will become more precise and detailed.
Moving from allostasis to a pre-chronic disease state (stage B) is often unnoticed until the signs of chronic disease risk become imminent.
Through the accumulation of stressors or allostatic load, a person moves from Stage A to Stage B. Omic technologies are helpful in Stage A to determine genetic disposition to a disease before signs of allostatic load and clinical biomarkers exhibit.
Stressors manifest as noticeable signs or biological expressions of disease. Diagnostic testing can detect early disease and biological dysfunction indicators, but the individual is often unaware of them. Examples include elevated blood glucose levels (i.e., prediabetes), hypertension and high blood cholesterol. Chronic inflammation is an important sign of disease risk. In this approach, lifestyle habits such as engaging in below-normal levels of exercise and excess body weight would be considered signs of increased chronic disease risk.
Patients at Stage B can benefit from preventive interventions to eliminate stressors and return an individual to Stage A. In the absence of this, a patient's health will increasingly worsen.
Healthcare delivered today is typically initiated when patients present with disease symptoms, or Stage C, frequently treating the symptoms of disease rather than its underlying causes and dysfunction-causing mechanisms. Volume-based healthcare perpetuates this reactive cycle, where symptoms typically worsen without direct intervention until the allostatic overload reaches a threshold and chronic disease is diagnosed.
At Stage D, chronic disease is diagnosed, and treatment ensues. Traditional healthcare is delivered and up-titrated with pharmacotherapy, surgery, behavioral change and other interventions used to manage chronic disease. Even at this stage of health, patients in a precision health model can improve their prognosis, clinical status and quality of life. Environmental and behavioral factors are modifiable risks that directly impact wellness.
The function of the precision health continuum is to optimize the state of wellness, with an individual even having the potential to reverse their state of health. Stages A to D are dynamic and omnidirectional, directly affected by genetics, health, physical and social environment, and behaviors.
While not replicable in all diseases, type 2 diabetes is an example of a condition once considered chronic and progressive that is now regarded as reversible. Lifestyle and behavioral interventions at stages B, C and D have demonstrated reversal of prediabetes (a precursor to type 2 diabetes) and type 2 diabetes to normoglycemic levels. A digital health app, Low Carb Program, received global attention for reversing type 2 diabetes in an elderly patient diagnosed with the condition for over 23 years. The digital platform, which provides patients with structured diabetes education and behavioral change support to adopt a nutritious diet and increase physical activity, supported a 67-year-old male to reverse his condition in 12 weeks. The correct clinical decision can be made for any patient to optimize their state of wellbeing at any stage of the P5H framework.
There are 4 levels of intervention in the P5H continuum:
Level 1 interventions are delivered globally or nationally, also understood as public health. The World Health Organization is a leading example of an organization with a public health focus, working at a national level to improve health understanding and engagement. Governments and national organizations have their own health themes based on local needs that ultimately seek to optimize the health of their respective populations and prevent chronic disease.
Local communities often share similar needs and behaviors. An intervention at level 2 creates healthy environments and makes nutritious and affordable food readily available to individuals in local communities. Physical activity and mental wellbeing opportunities are provided, smoke and pollution are kept to a minimum, information and resources are provided on maintaining health and preventing chronic diseases, and healthy lifestyle behaviors are encouraged in health care systems. Interventions can be promoted wherever individuals live, work or engage with public services such as schools.
Interventions are only successful if an individual engages or participates in them. Level 3 interventions provide healthy lifestyle interventions, promoting physical activity, maintaining a healthy weight, dietetics, mental health or smoking cessation support.
Interventions are directed at the individual, with behavioral change as the primary focus. Digital apps offering health coaching are increasingly providing direct intervention support, placing individuals in a healthy digital environment aware of the importance of a healthy lifestyle, and increasing the ability and likelihood of patients to follow care plans. In reality, affordability and accessibility are critical components of healthy environments which provide the most significant inertia to change.
Specific, system-targeted interventions focus on dysfunctional physiological systems. Examples include bariatric surgery for patients diagnosed with morbid obesity or pharmacological interventions for hypertension. Most patients in a Level 4 intervention are in Stages C or D of health. Ultimately, methods of evaluating the success of precision healthcare could well include the number of people the approach can support from entering Stages C and D of health in the first place.
Level 4 interventions delivered to individuals in Stages A and B of health focus on optimizing behaviors, collection and feedback of data, and prevention of disease states, promoting a consumer approach to health and wellness which will evolve and improve the ability to deliver precision health.
Regardless of the stage of health or level of intervention required when an individual enters the P5H continuum model, the objective is to prevent future disease risks and adverse events, treat underlying causes, and improve lifestyle behaviors. As such, all intervention levels can and should be delivered at all stages of health.
Healthcare is shifting from a reactive model to a proactive model to address the growing burden of chronic disease and health in its totality and the societal impact of illness. Attempts to make healthcare more predictive, preventive, personalized, participatory, and scalable to a population level are significantly improving health and wellbeing across the health continuum.
Precision lifestyle medicine is fundamental to the success of efforts to prevent and control costly chronic conditions, improve the health of populations, and eliminate health disparities.
At the same time, system-level precision health approaches are transforming the way we understand common morbidities, why and how they are related, and similarly, how we can reverse some, if not all, conditions, whether through genetics, environment, or behaviors. The P5H continuum provides such a framework, classifying four distinct levels of health and intervention.
Not only does this approach encourage the maintenance of homeostasis, but it also promotes wellness and longevity - foci of precision health.
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