Defining Comorbidity: Implications for Understanding Health and Health Services

In ageing populations, there is an increase in the number of patients with more than one important health problem present at the same time: comorbidity or multi morbidity. As a consequence, comorbidity has a profound impact on patient care, and on the planning and structuring of health care services. Valderas et al [1] analyzed the literature of comorbidity and concluded that the concepts and definition of what comorbidity is, depends on the context in which it is encountered. They distinguish in this respect between clinical care, epidemiology and health services planning.

In the primary care population and under patients encountered in family practice, a large minority are under treatment for two or more chronic diseases [2, 3]. Currently, in the support of patient care and clinical decisions, a disease-specific approach dominates, with condition- specified quality and outcome criteria [4]. In this approach, ‘comorbidity’ heralds particular facts that may force clinicians to deviate from their disease specific delineation [5]. With ‘comorbidity’ a rule rather than an exception, it is in our view no longer acceptable to apply for patients with more than one chronic disease an ‘opt-out of standard practice’ approach. For that reason, it is important to develop a better understanding of comorbidity, as a universal patient characteristic. This common ground is what would lend importance of comorbidity in the context of patient care, epidemiology and health care services [1].

A more in-depth exploration of patient care and the underlying clinical decision making may help to get more insight in the nature of comorbidity. Although the research evidence of comorbidity is limited, practitioners demonstrate a systematic difference in their treatment of patients with and without comorbidity – and practice appears to be well ahead of science. An interesting example in this respect is provided by a recent study in the UK of the management of patients with depression [6]. Family physicians (FP) arranged for more care, when the depression was more severe. But this needs dependent approach was less clear in patients with chronic physical comorbid conditions, who in general received less interventions than patients with depression as their only condition. An interpretation of these findings could be that FPs are reluctant to add-on interventions [7]. This is in particular the case in prescribing multiple drugs because of patient compliance and potential interactions [5]. Generic interventions such as empowerment and lifestyle changes may be more attractive because they may treat more than one condition at the same time [8].

Next to the health problem as such, FPs explore in their encounters patients’ preferences, interests and expectations around their health problems. These patients’ preferences may often conflict with or be incompatible to, plain disease-centered reasoning and this will influence FPs’ clinical decision. Everyday practical examples are the aversion of medication, priority for pain reduction over causal treatment or preference for a non-demanding , non-embarrassing therapy. In reconciling the implications of disease status and patient preferences, the true FP decisions are made. And FPs have a professional opinion on what the disease status demands as well as what patients prefer. The depression study as a case in point stresses the need of gaining better insight in the process in of decision making . Exploration of the practical experience should focus on the aims and objectives patients and FPs have in seeking and prescribing care. This would change the determination of patients’ needs beyond the disease perspective to a patient, or person, centred approach.

Critical is the notion that a person centered approach is more than just pleasing the patient or merely prescribing his or her expressed preferences. Expectations and perceived needs are formed from patients’ and families’ medical life experience [9] – as different consecutive, or as co-existing, episodes of illness experienced. This is the experience they bring to the practice, and the ‘healing relation’ between patient and FP [10] is determined by the FPs’ responsiveness. That is how, in our view, comorbidity shapes the process and outcome of care. It is time to come to a much better understanding of how the different disease scripts and the individual context interact into clinical decisions that flow from it – on patient care, for the provision of health care services and on the epidemiology.

References 1. Valderas JM, Starfield B, Sibbold B, Salisbury C, Roland M. Defining Comorbidity: Implications for Understanding Health and Health Systems. AnnFamMed 2009; 7: 357-363.
2. Weel, C. van. Chronic diseases in general practice: the longitudinal dimension. Eur J Gen Pract 1996 2: 17-21.
3. Weel C van, Schellevis FG. Comorbidity and guidelines: conflicting interests. Lancet 2006;367:550-1.
4. Department of Health. Quality and Outcomes Framework. http://www.dh.gov.uk/en/Healthcare/Primarycare/Primarycarecontracting/QOF/index.htm (accessed August 18, 2009)
5. Boyd CM, Darer J, Boult C, Fried LP, Boult L, Wu AW. Clinical practice guidelines and quality of care for older patients with multiple comorbid diseases: implications for pay for performance JAMA 2005;294:716-24
6. Kendrick T, Dowrick C, McBride A, Howe A, Clarke P, Maisey S, et al. Management of depression in UK general practice in relation to scores on depression severity questionnaires: analysis of medical record data. BMJ 2009;338:b750
7. Van Weel C, Van Weel-Baumgarten E, Van Rijswijk E. Treatment of depression in primary care. BMJ 2009;338:b934.
8. Dijurgeit U, Kruse J, Schmitz N, Stückenschneider P, Sawicki PT. A time -limited, problem-orientated psychotherapeutic intervention in type 1 diabetic patients with complications: a randomized controlled trial. Diabet Med 2002;19:814-21.
9. Huygen FJA. Family Medicine – the medical life history of families. Nijmegen, Dekker en van der Vegt, 1978.
10. McWhinney IR, Freeman T. Family Medicine. Oxford, Oxford University Press, 2009, 3rd edition.

Competing interests:   None declared

Establishing A Faultline Between Co-Morbidity and Multi-Morbidity

Valderas et al (Annals of Family Medicine July/August 2009) point out that there is no general agreement on the meaning of the term ‘co-morbidity’ and related constructs such as multi-morbidity. Clinical practice is fraught with definitional difficulties and it is important, especially in the area of international research, that we have a strong conceptual approach and good working definitions for enrolment into managed care programmes and clinical trials.

The current interest in multimorbidity in primary care represents a focus for academics and researchers anxious to contribute at population and clinical levels. Valderas and colleagues provide an important insight in pointing out that co-morbidity has an emphasis on an index disease which is particularly useful in specialist care which has a strong orientation towards a single disease, or a single diseased system. Multimorbidity on the other hand focuses on the patient as a whole without emphasis on any single condition.

This insight represents an important difference between specialist and primary care in the approach to chronic disease management. Much of the enthusiasm for multimorbidity in primary care research is that it echoes the reality of clinical practice. In the July issue of the Annals, Stange and Ferrer, point out that primary care is associated with apparently poorer quality of care for individual diseases but paradoxically with similar functional outcomes, better quality health and greater equity for communities and populations than specialist care. They call it the primary care paradox. Is it that ‘good enough’ primary care makes all the difference? The faultline between co-morbidity and multimorbidity is an important one.

Co-morbidity is intuitive, predictable and can aggregate specialists and technology around it. It can also, to paraphrase Julian Tudor Hart, remain unsullied by community and societal concerns. Multi-morbidity is the reality of clinical life in primary care and the definitional challenges posed by co-morbidity pale are fewer when it comes to multimorbidity. It does however represent intellectual and professional challenges for us to place our mark on the chronic illness map. It provides an opportunity for primary care to outline the scope and scale of our role to payers and patients alike.

The paper by Valderas et al demonstrates that much more work needs to be done in developing the patient perspective in terms of social, physical and psychological constraints. Outcome measurement is more of a challenge in multimorbidity than in co-morbidity where at least specific diseases can be the focus. Co-morbid conditions share aetiological or risk factors whereas multimorbidity incorporates additional management challenges such as the treatment for one condition exacerbating another.

We are nonetheless on the way in primary care in explaining the potential of cost-effective, equitable, competent, clinical care for common chronic diseases that affect the majority of our patients.

Tom O'Dowd & Susan Smith
Trinity College, Dublin

Competing interests:   Engaged in research on multimorbidity