Overview 

It is well established that athletes have a lower risk of cancer due to a healthy lifestyle of eating correctly and exercising to maintain a healthy body. However, contact sports are an area of high risk of injury which has been questioned whether this injury could cause malignant changes in the body. In this article, we go into some of the arguments that people have given for cancer risk and which of these are myths, and which require more research for a definitive answer.

Skin changes

Friction 

Rai et al determined a causation between wearing tight clothing around the waist and a type of squamous cell carcinoma called Sari-cancer. However, this is only a case study of one individual, and as such the findings are not scientifically significant. The general idea is that constant friction in one area causes malignant changes in the skin. Therefore, if this theory was taken to contact sports, could constant friction from other athletes or clothing cause changes in the skin?¹ 

Eapen et al found that in 140 women, ringworm and hyperpigmentation were more of a concern with tight-fitted clothing than malignancy. They also concluded, however, that most women who had a high level of friction around the waist, had some form of skin change such as scaling or lichen.² 

Sun exposure

For sports that require a large amount of time outside, for example, rugby or American football, sun exposure may increase due to long training in the heat. Without appropriate protection, prolonged sun exposure can damage the skin, thus increasing the risk of skin cancer.³

Concussions

Concussion is another area of significant concern within contact sports. The method of injury is usually a quick jolt forward causing concussion, similar to that of a person in a car accident getting whiplash. 

Researchers at UCL have discovered that repeated concussions have an increase in the risk of brain cancer.⁴ One of the main findings in this large group study was that for a concussion to cause brain cancer, genetic mutations are also required for this mechanism to occur. 

Therefore, if people don’t have a genetic mutation that can be activated, then the risk of cancer from concussion would be minimal. They also found that the risk was 1% over your whole lifetime. 

Prevention 

Skin damage 

To reduce the risk of any type of skin changes from tight-fitting pads or other protective equipment, adequate hygiene and washing of these items should reduce the incidence of infection. It’s also important to make sure that protective equipment fits correctly so that it is not too tight for the wearer, but also not so loose that it causes unnecessary friction to the items moving during exercise.² 

Just like when not playing contact sports, sunscreen and UV protective uniforms will reduce the incidence of skin cancer. It is not performing sports that causes skin cancer, rather spending time outside without adequate skin protection causes an increased risk.

Concussions

Practical methods for reducing concussions involve using multi-impact helmets and monitoring people post-concussion, to eliminate the risk of permanent brain damage.

Contact injuries 

Violent bursts to the chest or genitals are another area of concern for people when debating whether constant damage to the area can cause malignant changes. For example, in roller derby and ice hockey, chest protection is available to reduce the impact of hits to the chest. However, it may actually be to reduce discomfort from bruising rather than to reduce the changes of fibrosis and malignant changes to the tissues. 

Genetics and cancer risk 

p53 gene

Parenchymal astrocytes (a type of glial cell in the brain) can alter neurotrophin secretion within the brain. They are also important in neurotransmitter creation. As well as many other functions, these parenchymal astrocytes have protective functions in the brain. 

The experiment used mice that had a brain injury. The astrocytes were then labelled with a red probe. The gene p53 was knocked out (this means that it was stopped from working). This is a gene that is used to prevent us from getting many different cancers. Another group of mice was left with a healthy, working p53 and another group had p53 inactivation without brain injury. 

It was found that inflammation causes the astrocytes to go from a branched structure to a more rounded shape. This suggests that astrocytes are more likely to turn into gliomas (brain cancer) when there is inflammation or brain injury.

Research on animals has many different ethical implications and there is also the possibility that just because a biological mechanism works one way in mice, it may have a different mechanism in other animals such as humans.

Monteiro et al found that people with traumatic brain injury had a higher incidence of developing brain cancer.⁷ However, Dr Alvina Lai in the UCL Institute of Health Informatics found that the risk of developing brain cancer was still only 1%, but also four times more likely than for a person who has not experienced a head injury. 

Therefore, the main finding from this research is that the p53 gene needs to be mutated in order for inflammation or brain injury (which may be a result of a head injury from contact sport) for the mechanism of astrocytes changing into glioma. If someone isn’t predisposed to have this mutation, then concussion or other head injuries are unlikely to cause brain cancer. The main risk from head injuries in contact sports would be brain bleeds, bruising, and concussion, rather than cancer.

Examples of genetic mutations that cause cancer are vast. Breast cancer has been associated with BRCA1 and BRCA2 mutations.⁸ Lung cancer is associated with a vast range of different genetic mutations. Non-small cell lung cancer is associated with people who proportionally do not smoke, but carry genetic mutations such as KRAS and TP53.⁹ 

Other factors 

Another main point is that people who take part in contact sports may also be more likely to partake in less risk-taking behaviours in terms of cancer risk. For example, someone who is training at a high level in a contact sport may be less likely to drink excessively and may be more likely to eat healthily to benefit their training. 

It is important to note, however, that just because someone has a high-exercise lifestyle, does not necessarily mean that they will definitely have fewer lifestyle factors that cause cancer. 

Living in big cities with high amounts of environmental pollutants has also been associated with a higher risk of lung cancer, and this risk will be impossible to avoid whether the person has a lifestyle that reduces their overall risk of cancer. Moreover, lifestyle factors such as smoking and high BMI, for example, are established links to cancer and are considered to be modifiable. 

Summary 

In summary, genetics have a much more important role in determining a person’s risk of developing cancer than injuries as a result of participating in contact sports. Generally, random genetic mutations that happen spontaneously are the cause of most cancers. Whilst there is some evidence that injury can be involved in cancer pathways such as that of astrocytes turning into gliomas, a genetic component is also required for this pathway to work. 

Therefore, the risk of developing cancer is very similar in groups of people who compete in contact sports and those who do not. 

It is also important to look at the implications of bias in the reporting of head injuries in people who have already been diagnosed with brain cancer. For example, someone who has been diagnosed with brain cancer may be more likely to recount more instances of head injuries than someone who hasn’t had a diagnosis of brain cancer.

The fact that exercise increases muscle tone and effectively manages stress means that the benefits of regular exercise most likely outweigh the risks of injury or cancer.

Therefore, playing contact sports will actually reduce your risk of cancer, rather than increase it. 

Managing your use of protective equipment such as helmets and padding will also reduce the risk of injuries such as concussions and bone breaks. It is also important to note that if someone has a higher risk of injury, images of the area that is injured may aid in finding tumours that may otherwise go undetected.