For those who don't smoke, don't be cherished just yet with the fact that you will never get lung cancer, actually, you can. Even if non-smokers are associated with a lower risk of getting malignancies, lung cancer is still considered the leading cause of cancer-related mortality; approximately 10-15% incidence of lung cancer was noted among people who are non-smokers. Every single day, doctors have been advising hundreds of smokers regarding their risk of getting lung cancer; they failed to screen or note the possibility of a non-smoker to be affected with such problems.
Well, we can't really blame them (doctors), that's for sure, it's not easy to notice patients' relative risk of getting lung cancer when they didn't have any of the textbook-listed risk factors. Smoking has been regarded as one of the most important risk factors of lung cancer yet, quite a number of patients were not smoking nor have any family members or anyone related to them who were smoking. It's unfortunate but compared to people who were smoking, the appearance of the affected lung can be quite different hence giving us some sort of clue of its possible aetiologies; well, unless it has progresses to a severe form of lung diseases.
There are a lot of studies which have been conducted to investigate the incidence of non-smoker related lung cancer in the various part of the world. Back in 1999 to 2003, the percentage of non-smokers in California being diagnosed with lung cancer increased from 19% to 26%. The result of this study was also confirmed by a study which was conducted in Japan that ended in 2004; in that particular study, the number of non-smokers who are diagnosed with lung cancer increased by a whopping 17% from 16% to 33%. There are a few hypotheses that can be drawn from all of those studies:
- Women are usually affected
- The pattern of incidence seems to be dependent on geographic variation. Asia has been found to have a higher incidence of people being diagnosed with lung cancer (people who are non-smokers) compared to other countries.
Regarding the first hypothesis, the real reason behind it is still unknown. There are other risk factors which can be analysed to understand why non-smokers were affected with such condition:
- Exposure to carcinogenic compounds (occupational or domestic exposure)
- Exposure to a certain ionising radiation
- Diet
- Environmental factor (exposure to air pollution, arsenic compounds or asbestos)
- Any previous history of lung diseases
- Genetic predisposition
Oh, wait! I forgot about secondhand smokers, didn't I? This is one of the top listed implications which often being ignored as the potential threat, in this context, we are referring to the relative risk of people to develop lung cancer. There are a few names which have been given to describe people who inhaled cigarette smoke such as sidestream smoke, passive smoker or environmental tobacco smoke, nevertheless, the risk of developing certain conditions inflicted on people who smoke are almost the same provided they were exposed for a certain duration which can't simply be determined based on a specific factor.
Some secondhand smokers could develop pulmonary complications a few years after constant exposure and some don't even experience any of the symptoms; whether or not you will be inflicted by diseases related to inhaling cigarette smoke can be multifactorial. Otherwise, if we want to put some numbers into the risk of getting lung diseases, smokers are ten times likely to be diagnosed with lung cancer, six times likely to be diagnosed with chronic obstructive airway diseases (COAD) and two times likely to develop heart complications as opposed to the general population. People who live with someone who smokes might be exposed to almost the same risk to develop all of the mentioned conditions although the severity of diseases might vary from mild to moderate and most of the time, they are treatable.
Looking back to the history of lung cancer, it made me wonder, why on earth they wouldn't want to do something about the increased in people who smoke; when I said do something about it, I meant something much more aggressive instead of imposing a higher tax to the tobacco-related company. Probably tobacco companies made billions and contribute to the large proportion of a certain country's economy, but the association between smoking and lung cancer have been apparent since the early 1900s, even the data regarding secondhand smokers have been made available since 1930s.
In Europe and North America, lung cancer has been regarded as one of the rarest forms of cancer in 1912. People have been getting lung cancers mainly from environmental pollutants as manufactured tobaccos haven't been commercialised and introduced to the public in both of the regions just yet. The situation is a little different in Britain as people have been smoking since the Crimean war in 1854. Lung cancer caused by tobacco smoke has taken its place in Britain between the year of 1868 to 1885. By then the percentage of getting lung cancer was 0.2% but the figure increased ten-fold by the year of 1905 to 2%; currently, lung cancer has been regarded as the leading of cancer-related mortality, globally.
Once, it was thought that smoking would cause a specific type of lung cancer called the small cell carcinoma while non-smokers were usually diagnosed with the other type called adenocarcinoma of the lung, but nowadays, the number of smokers who were being diagnosed with adenocarcinoma have increased rendering the previous hypothesis moot. It's unknown whether the type of lung cancers between non-smokers and smokers can be distinguished by observing different histopathological changes, the only thing study has proved all this while is that different gender has a different likelihood of developing certain cancer type.
A study in Poland which was conducted in 2002 involving 20,567 subjects has found that males are more likely to be diagnosed with small cell carcinoma of the lung regardless of the smoking status while females are more likely to be diagnosed with adenocarcinoma. It's not until a later study which was conducted in Korea (2005) that found that each subtype is not only influenced by gender but also probable environmental influences since the number of men being diagnosed with adenocarcinoma has increased compared to small cell carcinoma. Although earlier, I have stated that we can't really determine smoking behaviour by the histopathological features of the patients' lung cancer, non-smokers are usually diagnosed with adenocarcinoma compared to smokers which are usually diagnosed with small cell carcinoma; though the incidence of adenocarcinoma has increased lately.
A study which was conducted in 2004 to investigate the effect of secondhand smoke on animals has shown an association between lung cancer and involuntary smoking.
Mauderly and colleagues, using an animal model, found that whole-body exposure in rats to cigarette smoke increases the risk of neoplastic proliferative lung lesions and induces lung cancer
It's unfortunate for a non-smoker to be married to someone who smokes because we can assume that involuntary smoking would be inevitable which can cause airway epithelial lesions that could lead to lung pathology as demonstrated by an autopsy study which was conducted in Greece (1992). It's relatively unknown where would be the most an individual would receive a secondhand smoke. Is it at home? At the office? At the restaurant? According to a study conducted by The National Human Activity Pattern Survey (NHAPS), most of the secondhand smokes were contributed in their own residence (husband, wife or children) but quite a significant figure which were contributed by other places (office, bar, restaurant etc.).
This is why by asking questions regarding smoking behaviour of spouses can be underestimating how much non-smokers have been exposed to secondhand smoke. A study which was conducted in 2004 by Brennan P. et al has found that non-smokers would have a 23% risk of contracting secondhand smoke in their own residence and 27% risk of contracting secondhand smoke in their workplace. Even though it is difficult for us to determine who would be at risk of getting lung cancer especially if they were non-smokers, some advice regarding smoking behaviour should be extended to the spouse who smokes. In the United State, death from lung cancer among non-smokers have been recorded at 24,000 per year and that is quite a significant figure.
Just because you refrain yourself from smoking, doesn't mean you are protected from lung cancer. If you are a smoker, think about how your behaviour can affect others.
References: [1], [2], [3], [4], [5]
All images were taken from Pixabay
Images: [1], [2], [3], [4], [5], [6]
