Lung Cancer: An Epidemiological Study of a Degenerative Condition:

Worldwide lung cancer is the most common cause of cancer related deaths and thus, responsible for approximately 1.3 million deaths per year. This essay aims to explore the distribution of lung cancer deaths worldwide and look at the epidemiological link between smoking and lung cancer incidence in the USA.

What is lung cancer?
Lung cancer is defined as “uncontrolled cell growth in the lungs”. It is a degenerative condition, by which we mean it is non-infectious (not predominantly caused by pathogens). It has a number of symptoms, including: shortness of breath, coughing up blood, chronic coughing/wheezing, chest pain or pain in abdomen, weight loss and loss in appetite, and lethargy/fatigue. Lung cancer is caused by a number of factors, including smoking, which is estimated to account for around 87% of lung cancer cases in the US. Other causes of lung cancer include background radiation from radon gas (which is naturally occurring), asbestos fibres (inhalation of which can cause lung cancer in conjunction with smoking), viruses such as HPV (which are not proven to cause lung cancer in humans, but are known to cause lung cancer in animals, and uncontrolled cell growth in humans) and particulates in the air.

World Distribution of Lung Cancer:

The above map shows the number   of deaths from tracheal, bronchial and lung cancers per 100,000 people for countries around the world. It can clearly be seen that the North American countries (the USA, Canada and Greenland) as well as some Eastern European countries (particularly Poland and Hungary), some Middle-Eastern countries (Turkey, Iraq) and some Asian countries (Kazakhstan, Mongolia, China, South Korea) have the highest rates of deaths due to Lung (and other related respiratory) cancers, at above 35 deaths per 100, 000 people. This is followed by other European countries (UK, France, Spain etc.), Asian countries (Japan, Indonesia, Malaysia etc.) and Oceanic countries (Australia, New Zealand), as well as some South American countries (Argentina, Uruguay). The African continent contains the majority of countries with fewer than 10 deaths per 100, 000 people, however other countries with low figures for deaths due to lung (and related) cancers include India and its neighbouring countries to the west, Middle Eastern countries (other than the ones previously mentioned), and some south American countries.

From this basic analysis of the map, it would be sensible to suggest that there is some sort of trend between development and lung cancer death rate per 100, 000 in countries around the world, as it is obvious that the highest rates are to be found in some of the most developed countries (and continents) in the world, with lowest rates found on the African continent, which is the least developed. This can be explored a bit further when we compare the above map with a map showing the GDP per Capita figures for countries around the world.

By comparison of the above maps, we can see that, in many cases, there appears to be a link between GDP per capita and lung (and related) cancer death rate. The USA and Canada both have very high (US$30,000+) GDP per capita, and also a very high lung cancer death rate. Europe has reasonably high levels of both, as does Oceania. Africa has generally low levels of both lung (and related) cancer death rate and GDP per capita. However, although there seems to be a visible link on the map, running a statistical test on all of the data such as Spearman Rank correlation would show that, despite the fact there is a positive correlation between the two datasets, it would not be significant enough for us to accept the hypothesis that there is a direct link between GDP per Capita and Lung (and related) Cancer death rate per 100, 000 people.

Therefore, there is not enough statistical significance to show that lung cancer is more prevalent in countries with a high GDP per Capita, but there is some form of positive correlation, suggesting that lung cancer is more prevalent in MEDC’s than LEDC’s. As geographers, and as economists, we have to ask ourselves why this is the case. There are a few possible explanations for this, presuming that the link is indirect considering that we’ve rejected the possibility of a direct link. The first of these explanations is that people generally live longer in MEDC’s than in LEDC’s and, as a degenerative condition, lung cancer is more prevalent in older people, so it follows that there is a greater incidence of lung cancer related death in MEDC’s than LEDC’s simply because people live long enough to get it (rather than dying from infectious diseases such as malaria and AIDS). Another possible explanation is that there is greater incidence of smoking, the major cause of lung cancer, in MEDC’s than in LEDC’s, as cigarettes are more readily available in MEDC’s than in LEDC’s, and a higher proportion of the population in MEDC’s smoke than in LEDC’s.

Smoking and Lung Cancer in the US – An Epidemiological Link:

The above maps show lung cancer incidence in US states compared to the percentage of the population that smoke in those states. It is even easier to see a link between these two datasets from the maps than it was for the GDP per Capita vs. Lung (and related) cancer death rate (per 100, 000) map, as the states with the highest prevalence of lung cancer (shown in dark grey on the map) are the same as the states with the highest percentages of people who smoke. There is also a noticeable trend of low lung cancer rates in states west of Nebraska and Texas (with the exception of Nevada, which also has a high percentage of smokers), and relatively low percentages of the population are smokers in these states (especially California, Utah, Montana and Washington), however the rates of lung cancer per 100, 000 people is still far greater than in African countries such as South Sudan and Malawi. There are only a couple of states which seem to muddy the waters in terms of the direct link between smoking and lung cancer: Colorado, New Mexico and Wyoming, which have a relatively high percentage of their population smoke compared to their lung cancer incidence per 100, 000 people, and Maine, which has a relatively high incidence of lung cancer compared to its percentage of the population that smoke. However these are insignificant anomalies compared to the overall epidemiological trend shown here.

If there is a similar trend worldwide to the trend shown on these maps of the US linking smoking to lung cancer, then it would be quite reasonable to suggest that there is a direct link between lung cancer incidence worldwide and smoking. A link between GDP per capita and percentage of the population that smoke for countries around the world would confirm whether or not smoking is responsible for an indirect positive correlation between GDP per capita and Lung cancer rates worldwide.

In the final analysis, if there is no link between GDP per capita and percentage of the population that smoke, however, then the other theory – that there is a high rate of deaths from lung (and related) cancer in MEDC’s compared to LEDC’s simply because people live long enough to die from a degenerative condition such as lung cancer may be more plausible. However, if the other theory turns out to be correct, then we may be faced with the bizarre conclusion that improved healthcare leads to a higher rate of deaths from lung cancer. *

*Though only in the sense that improved healthcare stops people from dying from infectious conditions earlier, so people are more likely to live long enough to obtain lung cancer and because there are more cases, there are more deaths.

Contributed by Joe Abell

One thought on “Lung Cancer: An Epidemiological Study of a Degenerative Condition:

  1. I’ve been browsing online more than 3 hours today, yet I
    never found any interesting article like yours. It’s pretty worth enough
    for me. In my view, if all web owners and bloggers made good content as you did,
    the net will be a lot more useful than ever before.

Leave a Reply

Your email address will not be published. Required fields are marked *