Defining Comorbidity

Defining Comorbidity

A finding

It is not unusual for a chronically ill person has other health problems. This can be other symptoms such as chronic pain or fatigue or other diseases such as hypertension, heart disease, vascular disease, diabetes, cancer, osteoporosis, depression, chronic anxiety or neurodegenerative disease.

A recent study on a representative population shows that 42.2% of chronically ill people suffer from other chronic disease (Barnett et al., 2012). 23.2% face more than two additional diseases.

42% of people with one chronic disease are suffering from another illness

An accumulation of difficulties

A chronic disease does not stop at its symptomatic manifestations, to an isolated pathophysiological mechanism despite what some experts think of an organ.

A disease that is superimposed can be even more debilitating than the first become chronic and cause the patient’s death. For example, only a third of patients with a deadly disease such as COPD actually die from COPD (Salvany-Domingo et al., 2002).

In any case, diseases combine additional but not degrade exponentially to a patient’s health status, to cause more of disabling situations, for further altering the quality of life and for generating more collateral damage in families. Consultations are more frequent examinations are more numerous, treatments are more complex care is more complicated, opinions are less unanimous on what to do and not do, and the rest dependent on the financial side is more important. The future is more uncertain.


“A comorbidity is the presence of one or more diseases in addition to a first chronic disease” (Bousquet et al., 2014).

A chronic disease: the perfect breeding ground for the proliferation of comorbidities

Over time, become a chronic disease is a fertile ground for the development of comorbidities. In question :

– Residual effects of the original chronic disease,

– Complications during the treatment of the original chronic disease,

– Failure to follow medical prescriptions (adherence)

– The side effects of treatments,

– The cycle of deconditioning,

– A lack of resources to manage stressful situations,

– Food shortages,

– Risk behavior,

– The low support of relatives.

These determinants combine, intriquent, influence, potentiate. They further weaken the patient in his daily life. For professionals, the situation becomes more complex to provide optimal care approach. It requires thinking time, mostly to many. The evolution of the patient’s state of health is less predictable (Frey and Suki, 2008). The prognosis is less certain.

Aggravating factors

As if that were not enough, two factors come darken the picture. They play an accelerating role in the risk of comorbidity, advanced age on the one hand and the other social precariousness.

After 50 years, 50% of chronically ill people suffer from at least one other disease. After 65 years, this figure is 80%. After 65 years, 62% of Americans suffer from at least two chronic diseases (Vogeli et al., 2007). The effects of aging are at work and potentiates the arrival of other health problems.

People without sufficient financial resources, isolated and / or low socio-cultural level are more vulnerable to comorbidities. In cancer for example, they benefit less supported and proposed accompaniments (Corroller-Soriano et al., 2008). They are caring less, less. They consult less. They have more difficulty responding to administrative requests.Both factors favor the increased number of comorbidities and worsen the original chronic disease.

Aging and social insecurity aggravate a chronic disease and promote comorbidities.

More complex and therefore more expensive to treat

A chronically ill patient consults her doctor four times a year on average. If there are 5 or more, the number rises to 14 times a year on average (Vogeli et al., 2007).

More comorbidities implies more serious consequences on health and more complex drug and non-drug interventions to implement, adjust and coordinate (Bousquet et al., 2014). The costs of supported explode (Vogeli et al., 2007), the co-pay for patients too.

The careful approach of comorbid patients is all the more complicated that our health system is essentially organized to treat disease at a time (Bousquet et al., 2014) and quite in emergency situations (acute crisis , exacerbation, infection, accident …).

Mechanisms involved

Biologically, the researchers found many metabolic disorders, cardiovascular, inflammatory, bone, muscle, brain in patients with multiple pathologies.

On the psychological level, including anxiety and depressive phenomena weaken even more patients (De Ridder et al., 2008). Cognitive disorders (attention, memory, analysis) are also at work. Wrong beliefs persist.

Socially, damaging consequences also arise: job loss, marital separation, family misunderstanding, insufficient financial reserves to cover the costs of treatment and care increasingly expensive dispersion of the friendly fabric.

On the environmental front, pollution, allergens, pesticides and other toxic agents easily affect people weakened by several chronic diseases.

A more complex issue than it appears

According Valderas et al. (2009), the concept of comorbidity should not stop to count the number of diseases in the strict sense that coexist with a chronic disease in a patient. Authors also include disorders (disorder in English), complications (Conditions English), health problems (problems healths conditions). These consequences are not strictly related to the initial disease, but it can be difficult to recognize or not as a comorbidity. Chronic fatigue, chronic stress, chronic pain, major handicap situations are examples. They are counted in studies and not in others who see them as symptoms, not diseases. Furthermore, the authors invite us to pay attention to the timing of associated pathologies (Valderas et al., 2009). They can emerge synchronously or shifted in time. Chronic disease like slow onset of dementia or diabetes may have started earlier diagnosis hear leaves. So it’s not that simple.

Comorbidities are more difficult to assess it looks depending on whether one takes into account strictly the number of diseases recognized by official classifications, their theoretical link with the initial illness or biopsychosocial consequences they generate. There is no consensus on the tool to be used to account for (Charlson Index, Cumulative Illness Rating Scale, Index of Coexisting Disease, Kaplan Index, Adjusted Clinical Groups, Diagnosis-Related Groups, Healthcare Resource Groups).

 What it means for Patients

Living with a chronic disease is not easy. But then several, life can become hell. Fortunately, there are therapeutic and preventive solutions to avoid the installation of these comorbidities, must still consult with professionals able to have enough experience and global vision to plan and properly coordinate these actions.

What it means for Health Professionals

What lurks a chronically ill person is the appearance of other diseases called comorbidities. Fitness trail will become an obstacle course. Y being attentive to each patient encounter is crucial to choose the therapeutic and preventive actions truly useful and track over time. Understanding the disease is a necessary but not sufficient condition. A comprehensive understanding of the person is mandatory because of comorbidities “roam” around the patient (and Préfaut Ninot, 2009).

What it means for Researchers

Science and technology sectorisent care. This analytical reasoning leads to analyzes of increasingly sophisticated, increasingly microscopic. It leads to spectacular feats (eg artificial heart) and extraordinary cures in certain diseases (genetic diseases for example). But for most diseases including chronic diseases, this approach and bring this vision to see only a small part of the many problems that a patient must do every day. Although many clinical trials testing a preventive or therapeutic solution to patients with chronic disease “pure”, it would be useful for researchers mention the number of associated pathologies, ie the number of comorbidities.

What it means for Policymakers

For simplification and understanding of complex human situations, we all make the mistake of thinking that a chronically ill person only suffers from a disease explained by a biological malfunction. We elude other difficulties and other comorbidities. This reasoning is encouraged by reducing medicine becoming every day more focused on scientific and technological (Sicard, 2002). It leads to only see part of the problem. Comorbidities are there to remind how a patient can not be reduced to his illness. The care for this person will require a comprehensive, coordinated and planned. It will be the fruit of a multidisciplinary work with the patient and not against the disease. This is the only way to avoid the explosion of health expenditure due to the resurgence of becoming chronic comorbid (World Health Organization, 2006).


Barnett K, Mercer SW, Norbury M, Watt G, Wyke S, Guthrie B (2012). Epidemiology of multimorbidity and implications for health care, research, and medical education: a cross-sectional study. Lancet, 380, 37-43.

Bousquet J, Jorgensen C, Dauzat M, Cesario A, Camuzat T, Bourret R, Best N, Anto JM, Abecassis F, Aubas P, Avignon A, Badin M, Bedbrook A, Blain H, Bourdin A, Bringer J, Camu W, Cayla G, Costa DJ, Courtet P, Cristol JP, Demoly P, de la Coussaye JE, Fesler P, Gouzi F, Gris JC, Guillot B, Hayot M, Jeandel C, Jonquet O, Journot L, Lehmann S, Mathieu G, Morel J, Ninot G, Pélissier J, Picot MC, Radier-Pontal F, Robine JM, Rodier M, Roubille F, Sultan A, Wojtusciszyn A, Auffray C, Balling R, Barbara C, Cambon-Thomsen A, Chavannes NH, Chuchalin A, Crooks G, Dedeu A, Fabbri LM, Garcia-Aymerich J, Hajjam J, Melo Gomes E, Palk S, Piette F, Pison C, Price D, Samolinski B, Schünemann HJ, Sterk PJ, Yiallouros P, Roca J, Van de Perre P, Mercier J (2014). System medicine approaches for the definition of complex phenotypes in chronic diseases and ageing. From concept to implementation and policies. Current Pharmaceutical Design, 20, 5928-5944.

Corroller-Soriano AL, Malavolti L, Mermilliod C (2008). La vie deux ans après le diagnostic de cancer. Ministère du travail, des relations sociales et de la solidarité. Paris: La Documentation Française.

De Ridder D, Geenen R, Kuijer R, van Middendorp H (2008). Psychological adjustment to chronic disease. Lancet, 19, 246-255.

Domingo-Salvany A, Lamarca R, Ferrer M, Garcia-Aymerich J, Alonso J, Felez M, Khalaf A, Marrades RM, Monso E, Serra-Batlles J, Anto JM (2002). Health-related quality of life and mortality in male patients with chronic obstructive pulmonary disease. American Journal of Respiratory Critical and Care Medicine, 166, 680-685.

Frey U, Suki B (2008). Complexity of chronic asthma and chronic obstructive pulmonary disease: implications for risk assessment, and disease progression and control. Lancet, 20, 1088-1099.

Organisation Mondiale de la Santé (2006). Prévention des maladies chroniques: un investissement vital. Genève: OMS Editions.

Préfaut C, Ninot G (2009). La réhabilitation du malade respiratoire chronique. Paris: Masson.

Sicard D (2002). La médecine sans le corps. Paris: Plon.

Valderas JM, Starfield B, Sibbald B, Salisbury C, Roland M (2009). Defining comorbidity: implications for understanding health and health services. Annals of Family Medicine, 7, 357-363.

Vogeli C, Shields AE, Lee TA, Gibson TB, Marder WD, Weiss KB, Blumenthal D (2007). Multiple chronic conditions: prevalence, health consequences, and implications for quality, care management, and costs. Journal General Internal Medicine, 22, 391-395.

To reference this Blog en Sante © article.

Ninot G (2014). Definition of comorbidity. Blog en Santé, L31.

© Copyright 2014 Grégory Ninot. All rights reserved.