The American Heritage Dictionary defines “complex” as “consisting of interconnected or interwoven parts; involved or intricate, as in structure; complicated.” While all humans are inherently complex, some patients are more challenging to care for than others. What then makes some more complex than others?
In answer, consider first the determinants of health, which include biology/genetics, socioeconomics, culture, environment/ecology, behavior, and the medical system.6–10
A common model is depicted in Figure .
Outcomes oriented model of the determinants of health
The associations of each determinant with health outcomes have been examined at the population level.7,11,12
However, the contribution from each determinant may vary in individual patients, and the relationships between the domains of determinants is not provided by the schematic diagram. The overall effect of the various determinants is therefore unclear. Furthermore, the model does not demonstrate how clinicians or the healthcare system should modify their interactions with patients, given the mix of determinants present, to optimize the health of the patient.
To address these needs, we propose the Vector Model of Complexity (Fig. ), using the principles of vector physics. Each health determinant from Figure (except healthcare) is conceptualized as exerting its influence along an axis, which intersects with the other determinants’ axes at a central point, the patient. Complexity can exist along each axis as a force which has both magnitude and directionality, defining vector v
. At any given time, a particular vector may exert a force increasing complexity, or alternatively, lessening complexity. In vector physics, an overall vector can be summed together (see also Appendix
); in the Vector Model, we conceptualize overall complexity as being similarly determined by multiple components. While the summary vector in physics can be precisely calculated, we do not know the mathematical relationships between the vectors of patient complexity. Nevertheless, the concept of a formal relationship among the different domains of complexity is clinically useful: according to the Vector Model of Complexity, two patients with similar biologic complexity may present greater or less overall complexity along any given axis, at a given encounter, depending on the relative sum of vectors at that time (Fig. ).
Figure 2 Interrelationships between influences on health that can lead to a complex patient: the Vector Model of Complexity. A patient’s complexity arises from different axes, but physicians often focus on the biological axis (underlined). Each axis is (more ...)
The Vector Model provides a basis from which to examine how the sixth determinant of health, medical care, should be adapted to maximize its impact on health. Clinicians focus primarily on the biological axis consistent with the emphasis in allopathic medical education on the biology of disease; however, influences along the other axes can either augment or diminish complexity along the biological axis. This results in similar treatment plans producing different results in patients with differing complexity. Assessment of all the axes of complexity may be an essential step in developing effective treatment plans for individual patients.
The interrelatedness between the axes is a key feature of the Vector Model, distinguishing it from previous conceptualizations of the determinants of health. The Vector Model explicitly acknowledges that the determinants are related. For example, recent immigrants may live in impoverished, environmentally disadvantageous locations (such as inner city slums); to have restricted financial means; and to lack health insurance. Cultural influences may exert pressures toward tobacco use, unhealthy diets, and mistrust in an unfamiliar approach to medical care. Cultural complexity therefore influences socioeconomic, environmental, and behavioral complexity. To represent these relationships, we add a web to the intersecting axes. The web has several appealing relevant features. Although they are often difficult to discern, the strands connect every aspect of the web, with each axis linked directly with all others, so that when one part of the web is perturbed, the entire web may be affected. The interconnections superficially appear tenuous, but may in fact be quite tenacious (Fig. ).
Table , organized by complexity vector, lists examples of factors that contribute to complexity, leading to differential effectiveness of medical treatment. Importantly, the Vector Model allows an individual’s level of complexity to vary over time, reflecting the dynamic nature of complexity. For example, individuals newly diagnosed with diabetes must make considerable efforts to modify diet and exercise, and to monitor blood sugar. Once incorporated into the patient’s lifestyle, these salutary health behaviors tend to diminish complexity at future encounters. Each encounter with the healthcare system can be thought of as a series of vector diagrams. Whether the provider and healthcare system prove helpful or effective depends upon both (1) the complete assessment of the patient’s complexity, and (2) the provider and healthcare system being equipped to respond.
Examples of Contributors to Differential Medical Treatment Effects and of their Consequences, by Patient Complexity Component Vector
The Vector Model in Action: Illustrative Case Vignettes
To better illustrate how these influences interact in patients, consider two illustrative cases (Fig. ).
Two patients with similar biologic but dissimilar socioeconomic, culture, environmental, and behavioral complexity
Mr. Smith has biological complexity, with multiple newly recognized conditions. However, his personal, family, and community circumstances exert stabilizing and supportive forces along social, cultural and environmental axes, diminishing the overall complexity confronting his treating physicians. Mr. Smith has the means to find culturally concordant doctors whom he can trust, enhancing motivation to quit smoking, make lifestyle changes, and take his medicines. His overall complexity vector along the biological axis is low (Fig. ), and his treating physicians need not modify their usual approach.
Figure 4 Complexity vectors for Mr. Smith and Mr. Jones. The arrows represent vector forces (V). In vector physics, these arrows can be added in space (for more details, see Appendix), and we propose an analogous relationship between the various domains of health (more ...)
In contrast, Mr. Jones has similar biological forces, but his other axes contribute forces toward greater complexity. Mr. Jones’ social support is much less than Mr. Smith’s. He has limited finances and may have difficulty paying for all the recommended medications, new diet, and follow-up care. He must balance his own self-care needs with his wife’s. His environment makes it difficult to exercise, and an unsafe neighborhood may contribute to stress. Mr. Jones’ overall complexity is greater than Mr. Smith’s.
Without a very different approach by his treating physicians than that used for Mr. Smith, Mr. Jones may conclude that his doctors do not understand his situation, become overwhelmed, and lose motivation to quit smoking and make difficult lifestyle changes. The Vector Model of Complexity therefore explains why a disease-focused approach (that is, considering the biological vector alone) works well in Mr. Smith but fails in Mr. Jones.
Using the Vector Model to Achieve Congruence
Explanatory models of sickness, a medical anthropological concept,13
provide a mechanism to use the Vector Model to create effective treatment plans. According to these explanatory models, “physicians diagnose and treat diseases (abnormalities in the structure and function of body organs and systems), whereas patients suffer illnesses (experiences of disvalued changes in states of being and in social function)”.14
Explanatory models of sickness fit well into the Vector Model of Complexity: they are determined by culture (national, racial, ethnic, occupational, or professional), religious beliefs, education and knowledge, social class [socioeconomic and cultural vectors]; gender, age, and personality traits [biological and behavioral vectors].
Hence, an important goal of the medical encounter is for the doctor and patient to develop “congruence,” or, a shared view of realistically attainable health care goals. The physician must assess each axis of the Vector Model, harmonizing the treatment plan accordingly. Congruence may enhance trust, satisfaction, respect for preferences, adherence with recommendations, salutary self-management behaviors, and mutuality in the evaluation of treatment outcomes.12–17
The influence of trust and perceived discrimination on adherence with treatment plans and with health outcomes supports the importance of congruence.11
The healthcare system must also be designed to promote congruence. While some healthcare systems can provide successful care to individuals with, for example, addiction, homelessness, and culturally unique needs, others can be distinctly unaccommodating for such patients.
Failure to achieve congruence between patient and provider may provide insight into why half of patients with chronic disease do not take medications as directed.18
Noncongruence may contribute to differential use of preventive services, diagnostic procedures, and therapeutic interventions by race/ethnicity, even when access to care, diagnosis, and severity of illness are similar. In fact, patient “non-adherence,” may be an excellent signal of (1) incomplete assessment of complexity and failure to modify the clinical approach accordingly, and/or (2) a healthcare system that remains ill-tooled to address the needs of complex patients.
Unfortunately, physicians receive little training on how to achieve congruence. While cultural competency is increasingly being added to educational curricula, these programs have unknown success.19
In fact, it is not clear how each axis of the Vector Model should be assessed, and validated instruments to capture aspects of each axis are primarily designed for research purposes. Evidence-based guidelines are a cornerstone to guide clinical management; how well do they help physicians care for complex patients?