Knowledge
A cough that has lasted more than 8 weeks is called chronic. It is a common reason to see a doctor, and it can and should be assessed systematically, because in most cases a treatable cause can be found.
This page is about long-lasting cough in adults and adolescents. If a child has a long-lasting cough, their GP is the right first contact.
FAQ
When it has lasted more than eight weeks. Under three weeks it is called acute and is most often due to a passing airway infection; between three and eight weeks it is called subacute.
If you are still coughing after eight weeks, it should be looked into. If you are over 40 and a current or former smoker, do not wait that long. Contact your doctor after four to six weeks, or as soon as your usual cough changes.
Yes. In cough-variant asthma the cough is the whole picture: no wheeze and no obvious breathlessness. It is a well-known reason asthma is missed.
Yes. It is called refractory chronic cough and is often described as a cough hypersensitivity, where the reflex itself has become too easily triggered. Treatment then aims to dampen the reflex rather than remove a cause.
Cough is classified by duration: an acute cough lasts less than 3 weeks and is most often due to a passing airway infection; a subacute cough lasts 3–8 weeks and is typically a prolonged after-reaction to an infection; a chronic cough has lasted more than 8 weeks. Chronic cough is common, and in most cases one or more treatable causes can be identified, but it takes a systematic approach, because the cause can rarely be heard in the cough itself.
In adults, chronic cough is most often due to one or more of these conditions:
Asthma can present with cough as the only or dominant symptom: so-called cough-variant asthma. The cough is often dry, worse on exertion, in cold air or at night, and can persist for years without wheeze. A third form is eosinophilic bronchitis, where the airways are inflamed in the same way but are not hyperresponsive. Spirometry and provocation testing are normal, while FeNO can be raised, and the cough responds to inhaled corticosteroid.
Chronic rhinitis or sinusitis can produce secretions that run down the back of the throat (post-nasal drip, also called upper airway cough syndrome). Typical accompanying symptoms are nasal discharge, a blocked nose and frequent throat-clearing.
Acid rising from the stomach can irritate the throat and airways and trigger cough, but reflux does not have to be acidic, or to cause heartburn, in order to cause a cough. That is why acid-suppressing medication does not always help the cough. The cough often comes after meals, when lying down or when talking for long periods.
Certain blood-pressure medicines of the ACE-inhibitor type can cause a dry, tickling cough (in some people only after months or years of use). A review of your medication is therefore always part of the work-up.
A cough can linger for weeks to months after an otherwise resolved airway infection, because the airways have become temporarily hypersensitive. It usually settles on its own, but should be assessed if it passes the eight-week mark. A few infections can drag on, whooping cough in particular, which can leave a cough for up to three months after the infection itself is over; mycoplasma too can leave a lingering cough.
Many years of smoking can in itself produce a persistent cough with phlegm, and the cough is often the first sign of COPD. Lung-function testing is essential for making the COPD diagnosis.
In many people several causes are present at the same time (for example both sinus secretions and reflux), and treatment then only works once every contributing factor is addressed. Smoking and other smoke exposure maintain and worsen a cough regardless of the underlying cause, so smoking cessation is a central part of any plan.
Cough-variant asthma is worth singling out, because it is easily missed. Here the cough is the entire presentation: no wheeze, no obvious breathlessness, nothing that looks like the asthma most people picture. The cough is typically dry, comes in bouts, and is provoked by exertion, cold air, laughter or lying down at night. It can carry on for years while being treated as an infection that never quite cleared.
The diagnosis is not made on the story alone, since the same pattern fits several of the other causes. It is confirmed with lung-function testing and, where needed, a bronchial provocation test, which can show whether the airways over-react. A further key feature is that the cough responds to bronchodilators. That distinction matters, because asthma treatment works well when the diagnosis is right and does nothing at all when it is not.
Some symptoms should always lead to prompt medical contact, because they need to be clarified:
Are you over 40 and a current or former smoker? Then do not wait for the eight weeks. Contact your doctor after four to six weeks of a new cough, or as soon as your usual cough changes.
Chronic cough is usually benign, and these symptoms do not necessarily mean that something serious is wrong, but they need prompt clarification. Contact your own GP during their opening hours. Outside your GP's opening hours: the 1813 medical helpline (the Capital Region of Denmark). For life-threatening symptoms: 112. The clinic is not an emergency service.
The work-up follows a fixed pattern: first the picture is mapped, then objective measurements are made, and finally the most likely explanation is tested with a targeted treatment trial.
We go through the duration and pattern of the cough, its triggers, accompanying symptoms such as nasal discharge and heartburn, smoking and smoke exposure — and all your medication. If you have been around small children while coughing, it is worth saying so, because whooping cough is contagious and small children tolerate it least well.
Spirometry with reversibility testing shows whether the airways are narrowed and whether the narrowing improves with medication. That is an important pointer towards asthma.
A chest X-ray is part of the initial work-up of chronic cough. The clinic does not take X-rays itself; the examination is arranged individually via an external laboratory.
A simple breath test measuring nitric oxide in exhaled air as a marker of the type of airway inflammation often seen in asthma and allergy.
If the diagnosis is still unclear, a provocation test can show whether the airways are hyperresponsive, as seen in asthma and cough-variant asthma.
Treatment is directed at the most likely cause and evaluated after an agreed period. If it does not help, the picture is reassessed. The next step is often to address a further, coexisting cause.
Note when the cough started, what triggers it, and whether you have night-time symptoms, heartburn or nasal discharge. Also bring a complete list of your medication, including over-the-counter products. That pattern often makes the first consultation considerably more focused.
In some people the cough continues even after the known causes have been looked for and treated. That is not a sign that the work-up has failed. It is a recognised condition in its own right, described as refractory chronic cough and often as a cough hypersensitivity, where the reflex has become so easily triggered that a change in temperature, a deep breath, a smell or talking is enough to set it off.
It matters because it changes what treatment can achieve. The aim is no longer to remove a cause, but to turn the reflex down. Speech and language therapy aimed at the cough has shown effect in randomised trials. The clinic does not provide speech and language therapy itself, but refers you for it when it is relevant. For some, a medicine that dampens the nerve signal is relevant. It is started under specialist care. One of these medicines is licensed specifically for unexplained chronic cough in adults that cannot be treated in other ways, while others are used outside their licensed indication (off label), so you should be prepared that treatment cannot always be offered to you. Neither is a quick fix, and both work better when the expectation is set correctly from the start.
Selected references behind this page.
The clinic assesses chronic cough systematically with lung-function testing, FeNO measurement and targeted treatment trials, and refers you for a chest X-ray when it is relevant. A referral from your GP is normally required; you can also be seen as a private or insurance patient. This page is general information and does not replace a medical assessment.