The Rising Incidences of Lung Cancer Among Non-Smokers: What are the Causes and Risk Factors Associated with this Disturbing Trend?
November is globally the Lung Cancer Awareness Month. It is an annual opportunity to raise awareness around the world about the second most common cancer. The World Health Organization (WHO) reported 2.21 million new lung cancer cases in 2020 alone. In the same year, the total number of deaths caused due to lung cancer was 1.80 million, followed by colon and rectum, accounting for 916,000 deaths1.
These alarming figures raise important questions – what causes lung cancer, and who is at higher risk of developing this life-threatening condition? Before we dive into the details, let us identify what lung cancer is.
About Lung Cancer
Lung cancer develops when the cells divide and grow abnormally in an uncontrolled manner. These cells eventually grow into a tumor or mass in the lung, making it difficult for the person to function effectively. If left undiagnosed and untreated, cancer can spread to surrounding tissues and organs or, even worse, penetrate deeply into different parts of the body, including the brain, liver, and bones2.
Who Develops Lung Cancer?
Smoking is the top risk factor for lung cancer. Approximately 90% of lung cancer cases are thought to arise from smoking3. The longer and heavier you smoke, the higher you are at risk. Not only cigarette smoking, but also pipe and cigar smoking increase the risk of developing lung cancer. Second-hand smoke is also a contributing risk factor.
People exposed through their work to chemicals , such as silica, asbestos, and diesel exhaust, are at increased risk of lung cancer. Moreover, those with a history of long term lung diseases, like chronic bronchitis and emphysema, are at high risk to develop lung cancer in the long run. Exposure to radon gas (a radioactive gas formed from uranium), sometimes found in houses and buildings, can also increase the risk of lung cancer. Lastly, people with close relatives (i.e., parent, sibling, or child) who have or have had lung cancer may be more prone to develop lung cancer4.
Other than these risk factors, researchers have also identified the reasons for an upward trend in the number of lung cancer cases among people who have never smoked.
Why are Non and Never-Smokers Developing Lung Cancer?
It is a known fact that smoking is the number one risk factor for lung cancer. But a retrospective study in the US found that 8% of over 12000 non small-cell lung cancer patients between 1990 and 1995 belonged to the never-smoker category. This trend escalated to 15% between 2011 to 20135. A similar study conducted in the UK found relatively higher diagnoses among never-smokers – an increase from 13% to 28% in the period between 2008 to 20146.
These research reports also observed that women who have never smoked have twice the risk of developing lung cancer than men. A 2020 editorial on Lung Cancer Management highlighted that approximately half of women detected with lung cancer globally belong to the never-smokers category, as compared to men accounting for 15% to 20%7. But what is the reason behind an increase in cases among non and never-smokers? And what measures can people who never smoke take to combat their risk of developing lung cancer symptoms?
- Genetic Mutations: Never-smokers are likely to have genetic mutations that contribute to lung cancer development. These genetic mutations, also known as targetable driver mutations, are biomarkers that medical experts can identify drugs and therapies that will control the spread of cancerous cells.
- Radon Exposure: This invisible, radioactive gas seeps into the homes through cracks, walls, ground, and floors. About 21000 lung cancer deaths every year are caused due to radon gas exposure8. Among non-smokers, radon exposure could contribute to a diagnosis of lung cancer.
- Environment Pollutants: Excessive air pollution and exposure to asbestos, arsenic, and diesel exhaust are believed to contribute to lung cancer development in people who do not smoke.
Beyond these, there are other factors like second-hand smoke and occupational exposure to cancer-causing agents, playing a key role in the increase of lung cancer in non-smokers.
How Can Non-Smokers Reduce their Chances of Developing Lung Cancer?
The symptoms of lung cancer are more or less the same among smokers, non-smokers, and never-smokers. However, the latter are not usually screened for lung cancer, which leads to a delayed diagnosis. Also, never-smokers are most likely to link their symptoms with other conditions apart from cancer at its early stages. Common symptoms of lung cancer include:
- Coughing up blood
- Persistent cough
- Loss of energy
- Shortness of breath
- Sudden weight loss
- Loss of appetite
- Chest pain
- Sore throat and difficulty swallowing
- Recurrent lung infections
- Swelling in the face or the neck
It is important to disclose to your doctor one’s family history of lung cancer or lung diseases and exposure to second-hand smoke, industrial pollution, radon, and other contributors.
There is no proven way to prevent lung or any other type of cancer. Still, you can lower your risk by making healthy lifestyle choices like staying active, eating nutritious food, avoiding excessive sunlight exposure and not smoking. Most importantly, being aware of your health is the key to everything. So talk to your medical professional on a regular basis. Diagnosis at an early stage can improve your chances of survival and reduce treatment costs.
- WHO. 2022. Cancer. Accessed on Oct 18th 2022.
- Cleveland clinic. 2019. Lung Cancer. Accessed on Oct 18th, 2022.
- American Lung Association. 2022. State of Tobacco Control 2022. Accessed on Oct 18th 2022.
- Cancer research UK. 2019. Lung cancer risks and causes. Accessed on Oct 18th 2022.
- Pelosof L et al. J Natl Cancer Inst. 2017;109(7):djw295.
- Cufari ME et al. Eur J Cancer. 2017;84:55-59.
- Ragavan MV and Patel MI. Lung Cancer Manag. 2020;9(3):LMT34.
- Yale Medicine. 2022. Lung Cancer in nonsmokers. Accessed on Oct 18th 2022.