How smoking affects the lungs

Smoking has a profound and damaging effect on the lungs, leading to severe conditions like chronic obstructive pulmonary disease (COPD) and lung cancer.

Professor Neal Navani, leading respiratory expert, provides an expert insight into how smoking harms the lungs, how early signs of smoking-related lung damage are detected, and the most effective strategies to quit smoking.

How does smoking damage the lungs?

Tobacco smoke contains over 7,000 chemicals, including tar, carbon monoxide and formaldehyde. When inhaled, these substances - many of which are toxic or carcinogenic - enter the respiratory tract, where they irritate and inflame the airways. Over time, this constant irritation leads to structural damage and the loss of lung function.

One of the most serious consequences of smoking is the development of COPD, a group of progressive lung diseases that includes:

• Chronic bronchitis: The airways become persistently inflamed and produce excess mucus, leading to a persistent cough and difficulty breathing.
• Emphysema: The alveoli (tiny air sacs responsible for gas exchange) are gradually destroyed, reducing the surface area available for oxygen absorption and carbon dioxide removal. This makes breathing increasingly difficult and leads to shortness of breath, chronic cough and fatigue.

Furthermore, smoking also impairs the function of the cilia (small hair-like structures that clear mucus and foreign particles from the airways). When the cilia are damaged, harmful substances linger longer in the lungs, further increasing the risk of respiratory infection.

Are there any tests that can assess early smoking-related damage?

Detecting lung damage early is key to preventing further deterioration. Several tests are used to assess lung function and identify early signs of smoking-related harm.

Spirometry is the most commonly used test. It measures the volume of air a person can inhale and exhale, and how quickly this happens. Two key values in spirometry are forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). A reduced FEV1/FVC ratio suggests airflow obstruction.

Other advanced lung function tests include the diffusing capacity for carbon monoxide (DLCO) test, which evaluates how well oxygen passes from the lungs into the blood, and plethysmography, which measures lung volume and airway resistance.

Additionally, high-resolution computed tomography (HRCT) scans can reveal structural changes in the lungs such as emphysematous changes and airway wall thickening. In recent years, clinical research has also explored biomarkers in blood, sputum, and exhaled breath that may indicate airflow inflammation or oxidative stress, though many of these are still under investigation.

What are the most effective smoking cessation strategies?

Quitting smoking is the single most important step a person can take to protect their lung health. Several evidence-based methods are available, including:

Nicotine replacement therapy, including patches, gums, lozenges and inhalers, help reduce withdrawal symptoms by delivering controlled doses of nicotine without the harmful chemicals in tobacco smoke.

Prescription medications such as varenicline, bupropion and cytisine are also effective. Varenicline works by blocking nicotine receptors in the brain, reducing cravings and the pleasure derived from smoking. Bupropion alters brain chemistry related to addiction and mood, helping alleviate withdrawal symptoms. Cytisine also reduces cravings for nicotine (https://www.bmj.com/content/387/bmj.q2563.full).

In addition, behavioural support significantly improves the chances of long-term cessation. Counselling - whether in person, online, or over the phone - provides support, personalised guidance, and progress tracking for people trying to stop smoking.

Can lung function improve after quitting smoking, and if so, to what extent?

The lungs begin to heal almost immediately once smoking stops. Within 24 hours, inflammation decreases and carbon monoxide levels in the blood drop to normal, allowing oxygen to reach tissues more effectively.

Over the course of several months, the cilia begin to regenerate, improving the lungs' ability to clear mucus. Breathing becomes easier and coughing is reduced. In terms of measurable lung function, the rate of decline in FEV1 slows significantly once a person quits smoking.

It’s important to know that some lung damage - especially from emphysema - is irreversible. However, quitting smoking can prevent further deterioration, improve quality of life, reduce chest infections, and help regain sufficient respiratory function to carry out daily activities and physical exercise with greater ease.

To book an appointment with Professor Navani, head on over to his Top Doctors profile today.