How long has that cough been going on? It's one of the first questions primary care clinicians may ask patients presenting with persistent cough—and for good reason. The duration of cough symptoms is not just a data point; it is a critical diagnostic tool that narrows your differential and guides management decisions.
Patient Care® spoke with Vukiet Tran, MD, an emergency, family medicine, and long-term care physician, during the 2025 FMX conference in Anaheim. In this segment, Dr Tran breaks down the clinical framework for classifying cough by duration and explains why these distinctions matter for diagnosis and treatment. Whether you're evaluating a patient in urgent care or managing chronic symptoms in your continuity clinic, understanding these timeframes will sharpen your diagnostic approach.
In this segment, Dr Tran covers:
- The specific time cutoffs that define acute, subacute, and chronic cough
- How different pathologies present within each timeframe
- Why the differential shifts dramatically after the 8-week mark
- When to start considering serious conditions like cancer, TB, and COPD
Dr Tran is the co-founder and president of the Canadian Physicians' Pension Plan, and an assistant professor in the Department of Family and Community Medicine at the University of Toronto.
The following transcript has been lightly edited for flow and style.
Patient Care: To start, could you briefly define how acute, subacute, and chronic cough are distinguished in clinical practice?
Tran: As the names suggest, acute, subacute, and chronic cough are categorized by duration. Acute cough lasts less than three weeks. Subacute cough lasts between three and eight weeks, and chronic cough is persistent beyond eight weeks—so anything beyond that two-month mark.
Patient Care: Why does making that distinction matter for diagnosis and management?
Tran: Because different conditions tend to present over different time frames. If the cough lasts less than three weeks, it’s usually due to an acute infection, most often viral, that resolves within seven to ten days. Between three and eight weeks, we’re often looking at less infectious and more inflammatory causes—such as upper airway cough syndrome, rhinitis, sinusitis, bronchitis, or postinfectious cough. Asthma and reflux or GERD also fall into that window.
When the cough lasts beyond eight weeks, we start thinking about chronic infections or other underlying causes. That includes upper airway cough syndrome or asthma that hasn’t been fully treated, as well as more serious conditions like cancer, tuberculosis, COPD, heart failure, or mycobacterial infections. The longer duration helps guide our differential diagnosis and clinical approach.
