Lung cancer remains a significant global health challenge, representing a leading cause of cancer-related deaths worldwide. In 2020, an estimated 2.2 million new cases and 1.8 million deaths were attributed to lung cancer, accounting for approximately 11.4% of total cancer cases and 18.0% of total cancer deaths globally. The burden of lung cancer varies across populations, influenced by demographic factors, lifestyle, environmental exposures, and biological predispositions. Understanding these influences provides insight into which groups face a higher likelihood of developing this disease.
Demographic Patterns
Lung cancer incidence and mortality rates exhibit distinct patterns across different demographic groups. Age is a significant factor, with incidence rates generally increasing with age, peaking among individuals aged 70-79 years. For example, in 2022, the age-standardized incidence rate was 23.6 per 100,000 globally.
Gender also plays a role, with men historically experiencing higher rates. In 2020, age-standardized incidence and mortality rates were approximately twice as high in men as in women globally. Lung cancer is the most frequently diagnosed cancer for men in 33 countries and the leading cause of death in 89 countries. For women, it was the second most commonly diagnosed cancer and the second most common cause of death from cancer in 2022.
Racial and ethnic disparities are also evident in lung cancer outcomes. In the U.S., Black males have had the highest age-adjusted lung cancer incidence rates among all racial/ethnic groups, at 73.5 per 100,000 compared to 63.5 per 100,000 for white males. This disparity persists even among never-smokers. Black individuals also face higher lung cancer mortality and are often diagnosed at a more advanced stage, with a median age of diagnosis for Black individuals being 67 years, compared to 70 years for white individuals. While Hispanics generally have lower lung cancer incidence compared to non-Hispanics, some subgroups can have elevated rates, sometimes influenced by higher smoking prevalence.
Major Lifestyle and Environmental Influences
Tobacco use is the primary lifestyle factor contributing to lung cancer. Smoking cigarettes is directly linked to about 80-90% of lung cancer cases. The risk increases with the duration and intensity of smoking.
Beyond active smoking, exposure to secondhand smoke also elevates lung cancer risk for non-smokers. Adults exposed to secondhand smoke face a 20-30% increased risk of developing lung cancer. This exposure is particularly impactful in domestic environments, with nonsmokers living with smoking spouses seeing a 41% increase in risk.
Emerging forms of tobacco products, such as e-cigarettes, are a concern. While research is ongoing, some studies suggest that former cigarette smokers who use e-cigarettes may have a higher risk for lung cancer compared to those who do not vape. Combining vaping with traditional cigarette smoking may increase lung cancer risk fourfold compared to smoking alone.
Air pollution also contributes to lung cancer risk. Outdoor air pollution, especially fine particulate matter (PM2.5), has been classified as a human carcinogen. It was estimated to contribute to 14.1% of all lung cancer deaths worldwide in 2017, making it the second largest cause after tobacco smoking. These tiny particles can build up in the lungs, damaging DNA and potentially leading to cancerous changes. Indoor air pollution, often from burning solid fuels for cooking and heating, also contributes to lung cancer, particularly in regions with lower smoking prevalence.
Occupational and Specific Chemical Exposures
Certain occupations and specific chemical exposures can increase an individual’s risk of developing lung cancer. Asbestos, a fibrous mineral once widely used in construction and manufacturing, is a known cause of lung cancer. Workers in industries such as construction, shipyards, factories, and power plants faced high risks of asbestos exposure. The risk of lung cancer from asbestos exposure is generally linear with exposure levels.
Radon gas, a naturally occurring radioactive gas that results from the breakdown of uranium in soil and rock, is another significant contributor to lung cancer risk. It can accumulate in homes and buildings, posing a risk to occupants, and also affects workers in underground occupations like mining. Other industrial chemicals and heavy metals, including arsenic, chromium, and nickel, are also recognized carcinogens that can increase lung cancer risk, particularly for those with occupational exposure.
Underlying Health Conditions and Genetic Predispositions
Beyond environmental factors, certain underlying health conditions and genetic predispositions can increase an individual’s susceptibility to lung cancer. Chronic lung diseases significantly elevate this risk. Individuals with chronic obstructive pulmonary disease (COPD) have an increased likelihood of developing lung cancer, even independently of smoking status. Pulmonary fibrosis, a condition characterized by lung scarring, substantially raises lung cancer risk, with some studies showing an increased incidence rate seven-fold higher. A history of tuberculosis infection also acts as an independent risk factor for lung cancer, with survivors having a 1.72-fold higher risk.
A personal or family history of lung cancer also indicates an elevated risk. If a close relative, such as a parent or sibling, has had lung cancer, an individual’s risk increases. While most lung cancer cases are not directly inherited, approximately 8-15% may involve hereditary mutations that increase susceptibility. This increased risk can be due to specific genetic mutations or shared environmental factors within a family. Genetic risk is more likely to play a role in lung cancer for individuals who are younger, female, and have never smoked.