Generality
"Comorbidity" is a term used in the medical field to indicate the simultaneous presence of several different pathologies, in the same individual.
More precisely, comorbidity can refer to:
- Two or more diseases that coexist simultaneously in a patient, but are independent of each other;
- Diseases or disorders that appear secondarily to the onset of an underlying disease.
In psychiatry, the concept of comorbidity may not necessarily refer to two distinct diseases, but also to the simultaneous presence of multiple diagnoses in the same patient.
Clearly, from the coexistence of different pathologies in the same person results a series of interactions that condition the course, the therapeutic regimen and the prognosis of the main and simultaneous illness.
In the medical-scientific field, the term "comorbidity" is often used as a synonym of comorbidity, to indicate the phenomenon of "presence of pathologies" or of "concomitant disease".
What does it mean?
Comorbidity is defined as the coexistence of two or more physical or mental disorders or diseases in the same individual .
The pathologies occur simultaneously or in sequence, independently of the primary disease or as a related medical condition. The latter sense of the term can cause confusion, if compared to the concept of "complication" . For example, if we consider coronary heart disease, diabetes mellitus can manifest itself as an autonomous comorbidity or as a complication with respect to the primary pathology; this discrimination is not immediate and simple, as both diseases are multifactorial and there are probable aspects both of simultaneity and of consequence. The same applies to intercurrent illnesses in pregnancy, such as gestational diabetes or pre-eclampsia.
In other cases, then, independence or relationship is not demonstrable, since the syndromes and associations present pathogenetic factors in common.
In the psychiatric field, comorbidity does not necessarily indicate two distinct diseases, but also the possibility of multiple diagnoses in the same patient (eg major depression, social phobia and anxiety disorder).
Comorbidity implies the overlapping and mutual influence of the morbid states in question.
The appearance in a subject suffering from a pathology (generally chronic) of another or more diseases, not directly caused by the first one, conditions the therapy, the patient's quality of life, the duration of a possible hospitalization, the course and the prognosis of the main disease and secondary or contemporary disorders.
For these reasons, comorbidity is associated with worse health outcomes, more complex clinical management and increased health care costs.
Because it is important?
Comorbidity should be considered for its implications related to the etiology, prevention and treatment of health problems in the same patient.
Importance for aetiology
When certain health problems occur in patients who have a certain primary pathology, the etiology of coexisting medical conditions must be investigated.
More precisely, the comorbidities could manifest for these reasons:
- There is a direct causal relationship between primary pathology and coexisting medical conditions;
- Common factors increase the likelihood of presenting a specific combination of disorders;
- There is an indirect causal relationship, so there is no causal link between the pathologies in question.
When defining the diagnosis, therefore, the doctor will need to accurately document the nature of all the pathological conditions, to recognize the possible mechanisms underlying the association and determine the most appropriate treatment.
Possible causes of comorbidity
- Anatomical proximity of organs affected by pathologies;
- Shared pathogenetic mechanism of some diseases;
- Cause-effect relationship between terminal pathological conditions;
- Illness resulting from complications of another problem;
- Pleiotropy (genetic phenomenon in which a single gene is able to influence multiple aspects and at least at first sight unrelated to each other in the phenotype).
The factors responsible for the development of comorbidities may include: chronic infections, inflammation, metabolic alterations, iatrogenesis (side effects or complications due to drugs or medical treatments in general), social relationships, environment and genetic susceptibility.
Comorbidity is a typical clinical feature of the elderly subject, due to the coexistence of multiple diseases related to aging .
Importance for treatment
Comorbidity is particularly relevant if concomitant disorders have a different clinical outcome. Therefore, when a treatment is established, attention to multiple health problems is important to establish the most appropriate regime for the case. In the management of patients who present different comorbidities at the same time, this approach can translate into a better outcome: treatment for alcoholism and nicotine addiction, for example, may be more effective, if therapy is also provided for depression.
Importance for prevention
Rarely, prevention programs are aimed at addressing concomitant disorders in an integrated way, underestimating the fact that the knowledge of comorbidity is useful for assessing the cost / benefit ratio in the treatment of a particular morbid condition.
Indeed, understanding the nature of comorbidity can help to address the prevalence of these disorders in the general population, especially when diseases share the same risk factors and in cases where the presence of a disease increases the likelihood of developing another .
Comorbid diagnosis
For a doctor, identifying a comorbidity is not a simple process : before making a diagnosis, he must assess whether the clinical signs or behaviors he observes are characteristic of a given pathology or if they are justified by another type of disorder. The difficulty is that a symptom is often common to more than one disease .
For this reason, in the presence of a high probability of medical conditions coexisting with the primary pathology, a global approach is required that allows the identification of each disorder.
More precisely, during the diagnostic framing of a comorbidity, the doctor must consider and integrate the information about:
- The nature of coexisting diseases;
- The relative importance of the concomitant conditions;
- The chronology of presentation of the pathologies;
- The patient's general health status.
This practice makes it possible to make a more accurate diagnosis and to prescribe the most targeted treatment.
Charlson Comorbidity Index - Comorbidity Index
The Charlson Comorbidity Index is a simple and rapid method that predicts the life expectancy of a patient with a wide range of coexisting pathological conditions . This reference makes it possible to measure comorbidity and correlate it with the probability of survival and consumption of health resources.
Pathologies "tracing" (22 conditions in total) are grouped into 4 classes, evaluated from 1 to 6.
More precisely, for each of these diseases, a score (score) of 1, 2, 3 or 6 is assigned depending on the risk of death associated with each morbid condition, as follows:
- 1 point : myocardial infarction, congestive heart failure, peripheral vasculopathy, cerebrovascular disease, dementia, chronic bronchopneumopathy, connective tissue disease, peptic ulcer disease, chronic liver disease and uncomplicated diabetes mellitus.
- 2 points : hemiplegia, moderate or severe renal failure, diabetes with organ damage, tumors, leukemia and lymphoma.
- 3 points : moderate or severe liver disease.
- 6 points : malignant tumors, metastases and acquired immunodeficiency syndrome (AIDS).
The sum of the scores determines the life expectancy and allows a decision to be taken before undertaking a particularly aggressive treatment. For example, if the case is to treat a malignant neoplasm in a patient with heart failure and diabetes, it must be considered that the risks and costs of a therapy could be higher than the advantages that the patient can obtain. Despite the amplitude of the range, a score above 5 is, generally, an expression of important clinical commitment.
Charlson's comorbidity index has undergone numerous revisions and variations over the years; today, it can be performed with “on line” tools or in the form of a questionnaire (filled in by the patient himself) and is used above all in elderly subjects suffering from neoplasias, neurodegenerative diseases and chronic cardiopathies.
Comorbid treatment
The effect of concomitant pathologies on the general clinical picture, on the prognosis and on the treatment makes necessary a multidimensional evaluation of each patient, to develop a personalized care pathway .
Comorbidity can greatly influence the clinical presentation and course of the primary disease, but also the character and severity of the complications. Furthermore, the coexistence of several pathologies in the same patient worsens the quality of life, increases the possibility of fatality and limits or makes the diagnostic-therapeutic process difficult.
Comorbidity often leads to polypharmacy, ie to the concomitant prescription of several drugs of the same or different therapeutic areas. This makes it difficult to control the efficacy of the treatment and makes it possible for the sudden development of local and systematic side effects, especially in elderly patients suffering from multiple chronic diseases. These adverse reactions develop mainly due to drug-drug interactions (ie the ability of a drug to modify the effect of another drug administered later or simultaneously). In each individual patient, this risk increases in relation to the number of coexisting diseases and that of the prescribed drugs.
For this reason, the simultaneous treatment of multiple disorders requires a rigorous consideration of the compatibility of drugs, in addition to the need to classify health problems into comorbidities in terms of relevance to clinical management.
