Co-Occurring Conditions: What Is Comorbidity?

The medical term 'comorbidity' is not one you likely hear all that often, but it may be something you have experienced.

Comorbidity describes the existence of more than one disease or condition that a person is facing simultaneously. Comorbidities are generally long-term or chronic in nature.

It is important to distinguish the difference between a comorbidity and a complication, which at first glance may appear similar. A complication is a side effect or medical problem that develops during a disease or after a procedure or treatment. Comorbidities, however, are separate illnesses or diseases experienced alongside your primary health concern. 

A pharmacist or those who have studied an online PharmD will understand the distinction between the two, which is important as having a comorbidity will often impact the type of medication you can take. While 'comorbidity' may feel like a scary word or concept, learning what it means and how it affects your health can help you understand your illnesses and conditions and take an active role in your healthcare treatment.

Examples of Comorbidities

'Morbidity' is a medical term that refers to the state of having a specific illness, disease, or condition. Adding a 'co' in front of this word means two or more conditions occurring together. Other terms that can be used to describe comorbidities include co-existing conditions, associated conditions, related conditions, multiple chronic conditions, and multimorbidity. 

An example of comorbidity might be an individual who has diabetes and is later diagnosed with depression. Diabetes would be the primary disease, and depression would be the comorbidity. 

A US study conducted in 2019 found that 84.1% of all inpatient stays were complicated by one or more comorbidities, and half of those stays included three or more comorbidities. 

The most common comorbidities were:

• Hypertension (high blood pressure) – 53.2%
• Diabetes – 26.4%
• Chronic respiratory (lung) disease – 20.5%
• Depression – 10%
• Drug abuse – 5%
• Alcohol abuse – 5%

The study also found that comorbidities increase with age. While 8% of adults aged between 18 and 24 had at least three comorbidities, nearly 73% of adults aged 85 or older had at least three comorbidities. 

Comorbidities were also shown to affect patient outcomes. Patients with at least three comorbidities had longer hospital stays, and in-hospital deaths were more likely when compared to those with fewer or no comorbidities. 

Researchers will often study people with specific conditions to see what additional illnesses they are living with. This has shed some light on common comorbidities for primary conditions, which include:

• Attention-deficit/hyperactivity disorder (ADHD), with

  • Depression
  • Anxiety disorders
  • Bipolar disorder
  • Substance use disorder
  • Personality disorders

• Arthritis, with

  • Chronic obstructive pulmonary disease (COPD)
  • Dementia
  • Heart Disease
  • Stroke
  • Diabetes
  • Cancer 
  • Obesity

• Heart failure, with

  • Type 2 diabetes
  • Sleep apnea
  • Obesity
  • High blood pressure

• Type 2 diabetes, with

  • High blood pressure
  • Dyslipidemia
  • Metabolic dysfunction-associated steatotic liver disease
  • Polycystic ovary syndrome
  • Obesity
  • Sleep apnea

These conditions will sometimes occur together because they share common causes or risk factors. However, this is not always the case, and they can be completely unrelated.

Likelihood of Having Comorbidities

As we age, we are more likely to develop health problems, so comorbidities increase with age, too. 

According to research, around 80% of Medicare costs in the US are spent on people with four or more chronic conditions. 

Research has also shown the disorder type, sex, and socioeconomic status of an individual may also impact the likelihood of comorbidities.

One study found those who lived in lower socioeconomic conditions were more likely to develop more than one health concern, likely 10 to 15 years earlier than those who live in more affluent areas, and the odds of having a mental health disorder increased with the number of comorbid conditions. 

How to Manage Comorbidities

Comorbidities are likely to complicate the management of your overall treatment plan. When you are diagnosed with more than one condition, there will be different symptoms and triggers for each, and they will likely need different management plans. 

When you have two or more conditions, you may have to take more than one type of prescription drug—this is known as polypharmacy. This can present challenges as there is the risk one of the drugs may interact with the treatment for another problem, but this is something your care team should be able to manage.

Your healthcare professional will have an in-depth understanding of comorbidities and the impact they have on your treatment. Learning and understanding your own comorbidities can help you talk to your healthcare provider and ensure you play an active role in building and implementing your healthcare treatment plan.