Which Countries Have the Highest Rate of Lung Cancer?

Lung cancer is the most common cancer worldwide with an estimated 2.09 million new diagnoses and 1.76 million deaths in 2018, according to the World Health Organization (WHO). Lung cancer is also the most common cause of death from cancer worldwide, responsible for nearly one in five cancer-related deaths.

The disease remains the most common cancer in men worldwide, particularly in Central Europe, Eastern Europe, and Eastern Asia where incidence rates are high. In women, the rates are generally lower, mainly reflecting differences in smoking habits between the two sexes.

There are numerous factors that can influence the rate of lung cancer in a population. While tobacco smoking remains the number one risk factor overall, other factors like air pollution and the use of solid fuels for heating and cooking can amplify the risk even in people who do not smoke.

These and other factors influence the incidence of lung cancers in different countries. In an effort to track (and ideally improve upon) these statistics, the collaborative Global Burden of Disease (GBD) project was launched in 1990 to determine which countries have the highest and lowest burden of this and other diseases. The latest data was published in 2017.

Key Factors

When assessing which countries have the highest rates of lung cancer—and why—epidemiologists with the GBD project look at several key factors.

Lung Cancer Incidence

Incidence refers to the proportion of people who develop a condition during a specific period of time, usually one calendar year. Incidence is generally expressed in the number of cases per 100,000. Therefore, a lung cancer incidence of 50 per 100,000 means that 50 people out of 100,000 were diagnosed with lung cancer during that calendar year.

For statistical purposes, epidemiologists look at overall lung cancer incidence to determine which countries have the highest rates. They will also offer incidence rates for women and men, in part to see if there is a consistent pattern between smoking rates and lung cancer diagnoses.

Smoking Prevalence

Prevalence represents the proportion of people who have a condition during a particular time period. In the case of lung cancer, epidemiologists look at the proportion of women and men who smoke and represent the prevalence in a percentage (%) value. Therefore, a smoking prevalence of 20% simply means that 20% of the population smokes.

In most cases, the smoking prevalence in women and men will closely align with the lung cancer incidence in women and men in that country. However, in countries like China, where the rate of smoking in men is 22 times that of women, the incidence of lung cancer in men is only twice that of women.

This suggests that other factors like poverty, lack of healthcare, secondhand smoking, and air pollution can also influence the incidence of lung cancer from one country to the next.

Outdoor Pollution

Air pollution is a major contributor to the development of lung cancer. These include diesel engine exhaust, solvents, metals, and dust that the International Agency for Research on Cancer has classified as carcinogenic (cancer-causing).

Air pollution is measured in values known as particulate matter 2.5 (PM2.5) and described in micrograms per metric cube (μg/m3). PM2.5 describes airborne particles of 2.5 micrometers in diameter or less that are able to get deep into the lungs. Higher values translate to worse air pollution.

The PM2.5 value for China is approximately eight times that of the United States and may account for why rates of lung cancer are high in Chinese women and men irrespective of their smoking history.

Indoor Pollution

According to the WHO, around 17% of lung cancers worldwide can be attributed to inhaled carcinogens caused by cooking or heating with kerosene or solid fuels like wood, coal, or charcoal.

This highlights another way in which poverty contributes to the risk of lung cancer. Epidemiologists measure the risk in the percentage of the population who rely on solid fuels for cooking and heating. The risk for women is especially high due to their role in food preparation.

Around three billion people around the world use open fires and simple stoves fueled by solid fuels or kerosene for cooking or heat.

Limitations

When determining the highest rates of lung cancer globally, epidemiologists don't usually use the incidence of death, also known as the mortality rate, to determine which countries have the highest rates of lung cancer.

This is because the death rate is influenced by many things, including the healthcare infrastructure of a country and the general health of the population. Developed countries like the United States, the United Kingdom, and France, therefore, have lower rates of lung cancer death rates compared to less wealthy countries like Montenegro, Serbia, and Bosnia-Herzegovina.

At the same time, the mortality rate is of less value when populations are small. Such is the case with a country like Samoa that has a population of less than 200,000. In some years, the death rate in Samoa may shoot to the top of the list if, say, 80 people die of lung cancer and the drop to the bottom if the number is below 10 (as it did in the 2017 GBD research).

This is not to say that mortality is inconsequential in characterizing a country's disease burden. The mortality rate can help epidemiologists understand why people are dying at the rate they are—whether the cause is related to the healthcare infrastructure, prevalent forms of a disease, or even genetics—and provides governments the means to address (and ideally mitigate) any modifiable factors.