Narrowly speaking, smokers cough is defined as persistent cough in smokers as a result of the irritation and damage of the lining of lungs from smoking cigarettes. In practice, smokers cough represents a spectrum of lung disease from mild irritation to advanced COPD. It is hard to separate pure smokers cough from beginning of more advanced lung diseases. For practical purposes, smokers cough can be seen as the first step towards development of COPD. As a practicing internist, I have evaluated and treated patients at different stages of their lung damage from smoking. I will give you a detail account of what happens at each stage and how smokers cough progresses into advanced lung disease.
Smokers cough: a basic review of lung anatomy
A basic review of what is inside your lungs will help you better understand smokers cough. Do not worry; you do not need to know any technical terms to understand basic mechanism of lungs. As you can see in the pictures, there are air pipes that go inside your lungs and divide into smaller branches. Eventually they become very small and finally each small branch ends up in a small balloon like sack.
This small sac is where the actual exchange of oxygen and carbon dioxide takes place.
To ensure smooth breathing, air needs to be able to go down all these air pipes and reach the air sacs while breathing in.
Similarly, air should be able to flow smoothly out from the air sack all the way out to the nose when you breathe out. With this basic knowledge, you can see how smoking related lung damage impedes smooth airflow. Although, I have explained smokers cough and ongoing lung damage in terms of discrete stages, please bear in mind that it is a continuous process where changes in one stage lead to the next. The end point of these changes always lead to COPD as you will see shortly.
Smokers cough: First stage of lung damage from smoking
Cigarette smoke is made up of many different particles and gases. When you inhale this mixture inside your lungs, your lungs try to protect themselves using several lines of defenses. Tightly packed cells called the epithelial cells of the air pipes guard the inner lining of your lung. They are the first line of defense against external irritants. They produce liquid mucous to help clean the inside of the lungs and clear the debris. They also have small hair like projection called cilia that literally sweep the mucus along with the dirty particles. The inner lining of the lungs also have immune cells that help to capture and kill invading organisms. Your immune system has the ability to recruit additional immune cells and inflammatory mediators to your lungs when needed to fight any invasion.
When the particles and gases in the cigarette smoke reach the inner linings of your lungs, the epithelial cells sense those irritants and produce more mucous. They try to clear the debris by sweeping with the cilia. They also initiate the cough response and help expel the dirt out of your lungs. When you start smoking, initial cough is part of the defense mechanism. As you keep smoking, this defense mechanism gets weaker. The epithelial cells start to lose their cilia and become less effective in clearing the particles. They produce more mucous but their ability to clear the mucous and irritants decrease. At this stage, the irritation and surface damage leads to persistent cough as your lungs try to free themselves of the irritants. When you have mostly dry cough everyday for at least three months, it could be smokers cough from the beginning stage of lung damage.
Smokers cough: continued damage beyond the initial stage
As you continue to smoke cigarettes, you will have further and more extensive damage in your lungs. The production of mucus keeps going up. Normally mucus is only produced in relatively bigger air tubes so that they can be cleared easily. When the irritation and damage of the epithelial cells continue, even smaller air tubes start forming cells capable of producing more mucus. When the amount of mucus in small air tubes reaches a certain level, it starts to get trapped. With mucus trapping, your cough gets worse and you begin to transition from dry cough to wet productive cough. Due to decreased debris clearance and accumulation of mucus, you may be susceptible to more frequent upper respiratory infections. Your immune system gets activated to build up a better defense system because of the increased susceptibility to infection. In the short term, this may be helpful to fight infection. However, the over-activation of immune system can cause long-term lung damage.
Smokers cough: chronic bronchitis and air tubes remodeling
When you start to have daily cough with copious amount of sputum production for at least 3 months, you meet the criteria to be formally diagnosed with chronic bronchitis. Other than significantly increased mucus production, there is significant inflammation from over-activation of the immune system when you have chronic bronchitis. The inflammatory immune cells infiltrate the epithelium. The inflammation results in enlargement of the mucous producing glands. The toxic gas and particles present in cigarette smoke continue to damage the surface of the air tubes repeatedly. The cells of the air tubes try to repair themselves back to normal. However, the surfaces of the air pipes lose their original structure because of the repeated damage and repair. This is called remodeling. It can lead to narrower air tubes.
Smokers cough: Airway obstruction
When the narrowing of air tubes becomes widespread, it can cause significant slowing down of the airflow inside your lungs. The airflow obstruction gets particularly worse when the tube narrowing involves small branches of the air tubes. When you get to this stage, you start to have wheezing sounds in your chest. Some of the wheezing may be loud enough for you to hear it yourself. At other times, you may not hear it but your doctor can listen to it with the help of a stethoscope. At this stage, you will have chronic productive cough associated with wheezing.
Smokers cough: Chronic obstructive pulmonary disease (COPD)
When the airway obstruction is permanent and associated with some degree of respiratory compromise, you have chronic obstructive pulmonary disease. It is the ultimate end game of smokers cough in most smokers. It is said that anyone who keeps smoking will get COPD at some point in his/her life if he/she lives long enough. It is a question of “when”, not “if”. However, there is a significant variation in the amount of cigarette smoking required to get COPD. Some people may get COPD with just 15 years of smoking while it may take 30 or even 40 years for others. It is true even if they smoked the exact same numbers of cigarette a day. Some people are born with a gene that makes them highly susceptible to getting COPD even from relatively small amount of cigarette exposure. When you have COPD, you will have some degree of shortness of breath along with smokers cough and wheezing.
At first, the shortness of breath may only be apparent with exertion. If you live a sedentary life and do not walk, run or climb stairs, you may not notice any shortness of breath. In those cases, the only symptom you have could be a feeling of low energy or being tired. You may attribute that to getting old or being overweight and not pay much attention.
If you feel tired and meet the following three criteria, you most likely have COPD:
- Have smoked for many years
- Have chronic smokers cough with sputum production
- Have wheezing
Although airway obstruction is one of the main problems in COPD, it is not the only one. Smoking can also damage your air sacs in addition to your air tubes. In some people, air pipe damage predominates while air sac damage predominates in others. In addition to that, smoking can also reduce the overall elasticity of your lungs and make them somewhat stiff.
Smokers cough: Air trapping or emphysema:
Emphysema is a component of COPD. Air trapping and airway obstruction are two main parts of COPD. In an individual patient, one of the two may predominate. In patients with emphysema predominant COPD, the air sacs get enlarged and saggy. As a result, air is trapped inside the air sacs and effective movement of air in and out of the air sacs is reduced. This results in inadequate gas exchange and can lead to respiratory distress. In these patients shortness of breath is usually more common that smokers cough or wheezing.
Smokers cough: Is it reversible if you stop smoking?
In the initial stage, the lung damage from smoking is completely reversible if you stop smoking. When your lung damage has reached the level of COPD, the damage is irreversible. It is hard to pinpoint the exact point in the progression of disease where it changes from being reversible to being permanent. There have been several studies trying to answer this question and they have a general idea but it is not very precise. In general it is thought that the changes can be reversed slowly if you stop smoking before there is any remodeling of the airways. However, individual response varies. In some people the inflammation from immune over-activation may be self-sustaining and may continue the damage for a long time. To be safe, it is best to stop smoking before you develop the symptoms of chronic bronchitis.
Smokers’ cough: Does quitting help when you already have COPD?
The changes of COPD are irreversible but that does not mean that quitting cigarettes is not important. In fact, quitting cigarettes is the only treatment that can help to halt the progression of disease. It is important to understand that lung damage from smoking is a continuous process. Just because you already have COPD does not mean that there is no further damage from smoking. COPD at any stage gets worse if you keep smoking. If you have bad air tubes, they get worse with smoking. If you have bad air sacs, they get worse with smoking. If you have bad productive cough with wheezing, it gets worse if you keep smoking. If you have bad shortness of breath, your breathing will only get worse if you keep smoking.
I hope that this article on smokers cough will encourage you to quit smoking early enough to avoid irreversible lung damage. Please share this article with your loved ones if you think it may help them. If you have any questions, please leave them in the comment below. I cannot give you any specific medical advice but I will be happy to answer your general questions about smokers cough.