Comorbidity
Definition
Comorbidity refers to the presence of two or more diseases or medical conditions occurring simultaneously in the same person.
Correct Scientific Usage
In clinical research, comorbidities are acknowledged because they influence disease progression, treatment response, and risk of adverse events.
Many trials exclude participants with multiple comorbidities to reduce variability and simplify analysis, even though such patients are common in real-world settings.
Common Misunderstandings
Comorbidities are often overlooked when applying research findings. People may assume that results showing benefit in healthy individuals will translate to those with multiple conditions, when evidence for that assumption may not exist.
There's also confusion about causation. Two conditions can be comorbid without one causing the other; they may share common risk factors or simply co-occur by chance.
Why It Matters
Most clinical trials exclude patients with significant comorbidities, yet most real-world patients—especially older adults—have multiple conditions. Understanding comorbidity helps recognize when research evidence may not apply directly to complex, real-world situations.
References
- Defining Comorbidity: Implications for Understanding Health and Health Services, Annals of Family Medicine
- Multiple Chronic Conditions: Prevalence, Health Consequences, and Implications for Quality, Care Management, and Costs, Journal of General Internal Medicine
Related Terms
Related Articles
- Why Most Health Studies Don't Apply Equally to Everyone
- What ‘Backed by Science’ Really Means
- Why One Study is Almost Never Enough