Comorbidity and Arthritis

Arthritis and Comorbid Conditions

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The terms "comorbidity" and "comorbid condition" are medical terms you will come across often when reading about medical studies and multiple chronic conditions. A comorbidity refers to one or more diseases or conditions that occur together with another condition in the same person at the same time.

Using rheumatoid arthritis as an example, there are comorbidities associated with the disease that are non-articular manifestations (i.e., conditions that affect body parts other than joints), occurring with higher frequency than would be expected in the normal population.

These include conditions such as subcutaneous rheumatoid nodules, vasculitis, neuritis, Sjogren's syndrome and Felty's syndrome. Although these conditions are not found in all rheumatoid arthritis patients, when present, they may influence treatment.

Comorbid conditions can also include diseases and conditions other than rheumatic conditions. It can refer to arthritis with diabetes, heart disease, or cancer as well. Conditions considered comorbidities are often long-term or chronic conditions. Other terms that are used interchangeably with comorbidity include, coexisting conditions, co-occurring conditions, multimorbidity, or multiple chronic conditions.

Comorbidty Statistics

According to the Centers for Disease Control and Prevention (CDC), nearly half of adults in the U.S. with arthritis also have at least one of the following 4 comorbidities: chronic respiratory conditions, diabetes, heart disease, or stroke.

Study results revealed that of U.S. adults with arthritis:

  • 24% also had heart disease.
  • 19% also had a chronic respiratory condition.
  • 16% also had diabetes.
  • Almost 7% had a stroke.

While heart disease was found to be the most common comorbidity with arthritis, stroke was the least common. There is no concrete answer regarding why it is common for people with arthritis to have comorbidities.

Speculation has pointed to non-modifiable risk factors as well as modifiable risk factors that are associated with arthritis and the comorbidities. In other words, they have things in common. Age is an example of a non-modifiable risk factor that would be common with most comorbidities. Obesity and smoking are examples of the shared modifiable risk factors. The CDC has emphasized the importance of remaining physically active to help arthritis as well as the comorbidity. 

The CDC also revealed that:

  • 49% of U.S. adults with heart disease also had arthritis.
  • 47% of U.S. adults with diabetes also had arthritis.
  • 31% of U.S. adults who are obese have arthritis.

Despite the emphasis on remaining physically active, 1 in 5 people with heart disease are physically inactive. With arthritis and heart disease as comorbidities, 1 in 3 people are physically inactive. Similarly, 1 in 5 people with diabetes are physically inactive. With arthritis and diabetes together, 1 in 3 are inactive. Arthritis clearly adds to the burden.

General Consequences of Comorbidity

Generally, comorbidity is tied to worse health outcomes, the need for more complex treatment and disease management, and higher health care costs. It's not unusual to be faced with managing multiple chronic conditions. Reportedly, 80% of Medicare spending goes to patients with 4 or more chronic conditions. 

Another point that researchers have considered, with regard to comorbidity, is chronology. It may be significant which disease occurred first. For example, arthritis and depression. Knowing whether arthritis or depression developed first may have implications regarding disease onset, prognosis, and treatment. When selecting from treatment options for comorbidities, it is also important to recognize and steer clear of treatments that are antagonistic.  

Sources:

Comorbidities. Data and Statistics. Arthritis. Centers for Disease Control and Prevention. Updated May 27, 2015.​
http://www.cdc.gov/arthritis/data_statistics/comorbidities.htm

Defining Comorbidity: Implications for Understanding Health and Health Services. Annals of Family Medicine. Valderas JM et al. July 2009.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2713155/

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