Runners and Cancer

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Top Contributors - Kapil Narale  

Introduction

It is known that Physical activity is beneficial for the body, and helps to prevents many cancers, including colon breast, and edometrium. However many outdoor activities, including running, pose as a risk factor for skin cancer due to the exposure to the strong ultraviolet rays, especially in the peak daylight hours.

This page is exploring two sides to cancer and runners: what may be risk factors for healthy runners that may lead to cancer, and how cancer affects patients who are already runners.

Exposure to the Sun

Exposure to the UV rays from the sun is a potent risk factor towards skin cancer. The knowledge, behaviour, and attitudes of such athletes towards protection from the sun seems to be quite limited or not present. It is commonly known that individuals who participate in outdoor sports such as running do not sufficiently protect themselves from the sun, which can be a factor leading to skin cancer.

It is said that UV exposure may be facilitated by a change in the sunlight's absorption spectrum to shorter wavelengths due to the hydration of the stratum corneum, thus decreasing reflection and diffusion. This results in a greater UVB transmission, and a greater sensitivity of moistened skin to ultraviolet rays. UV exposure can result in a dose- and time- dependent facilitation of damage to one's DNA. This effect can be accelerated with sweating, as discussed below.

A greater risk of developing skin cancer is correlated with sweating, which increases the photosensitivity of the sun-exposed skin. This induces skin photosensitivity and activity-induced immunosuppression. There is no material in sweat that is said to increase the sensitivity of the skin to sunlight. The sweating caused by an increased exposure to the sun, heat, and physical effort while running outdoors can cause an erythema reaction, which can lead to an increased chance of a sunburn.

UV radiation is a primary risk factor of malignant melanoma (MM), and non-melanoma skin cancers (NM-SCs). Melanoma and non-melanoma skin cancers seems to be common in marathon runners. Melanocytic nevi and actinic lentigines are common within marathon runners, which are related to the development of malignant melanoma. The incidence of these skin cancers is gradually increasing worldwide. It is the most common in Australia and New Zealand. However, these are most preventable types of cancers. Two-thirds of melanomas and 90% of other skin cancers are correlated with the overexposure of UV rays. Melanoma is associated with intense and frequent exposure to the sun, which can lead to sunburn. A study showed that lifelong exposure to the sun with outdoor running can be a risk factor for melanoma, which also relates to the duration of exposure.

Saquamous Cell Carcinoma (SCC) can also occur in marathon runners. This can be associated with prolonged exposure to the sun, and a high cumulative exposure.

Individuals with a lighter skin tone can be at an increased risk as well.

Protecting one's self from the sun's rays can help prevent skin damage and skin cancers. Exposure to the sun's rays causes both chronic skin damage and sunburn. Sunburn occurs with extreme exposure to the intense sun, which leads to an acute inflammatory response. The radiation from the sun causes suppression of the immune system, which can lead to the development of cancer. Runners who may be overtraining can result with tissue injury, which may lead to immunosuppression.

Prevention and Protection

It is important that runners are aware of methods to protect themselves from the frequent overexposure t0 the UV radiation, and with increased sweating. The level of sweating and environmental factors should be taken into account. This can help reduce skin damage in terms of sunburn, erythema, pigmentary disorders, photoaging, precancerous lesions, and skin cancers. There are many ways to protect from the intense sun rays.

Photoprotective agents can include:

• Natural agents, such as ozone, clouds, fog, pollutants, and the skin
• Physical agents, such as clothes (including sun protective clothing with UV protection factors (UPFs)), hats, or sunglasses
• Sunscreens, and
• Antioxidants, which are present in the diet, and reduce the oxidative effects from the exposure to ultraviolet radiation - this would include vitamin E (tocopherol), vitamin C, beta-carotene, and flavonoids.

Methods of photoprotection, and preventing skin cancer, can include: finding shade, minimising sun exposure in the peak sunlight hours, using sun-protective clothes, using sunscreen with an SPF of <30, covering your arms and legs with sleeves, and using hats and/or sunglasses. Sunscreens that are water resistant should be reapplied after 3 hours of perspiration.

In a study, it was seen that the most common protection from the sun used by runners was by wearing sunglasses. In terms of sunscreen application, 49% claimed they forgot to use it, and 17.3% found it uncomfortable. It is interesting to note that sun protection was more commonly used in runners who are women, elderly, completed fewer miles per week, with a lower BMI, and previously experienced skin cancer. In addition, it is seen that runners less than 45 years of age are more likely to experience sunburn. In a study, it was found that younger age, low Fitzpatrick skin type (I and II), or running for more than 3 hours a day, were risk factors for sunburn. I this study, the most common protective measures from UV radiation (from most to least common) were: sunglasses, sunscreen, wearing a hat, and protective clothing. A study by Christoph et al. mentions that older (between the ages of 35 and 54), fair-skinned (type I and II), and female runners have a greater awareness of skin cancer, and are more conscious of utilising protective measures. As well, individuals with a personal history of skin cancer had a higher photoprotection score, However this was not the case in individuals with a family history of skin cancer.

In a cross-sectional online survey, seven sun protective behaviours were compared to note the differences. These seven behaviours included the use of, sunscreen on the face and/or body, a hat, sunglasses, long sleeves, running int he shade, and avoiding running in the midafternoon sunshine. About 54%-84% of runners claim that they occasionally use some of these methods, but only 7-45% claimed that they frequently use these methods of protection. From individuals who did not use sunscreen, 49% claimed they forgot, 17.3% found it uncomfortable, and 6.1% wanted to maintain a tan, while 5.1% wanted to take advantage of the vitamin D intake. Other reasons people did not use screen were they didn't believe they were at a higher risk of skin cancer, being ignorant of sunburn or wrinkles, and the expense of the sunscreen. When noting sun exposure behaviour, 39.2% had a fear of skin cancer, 28.7% were uncomfortable, and 15.8% wanted to avoid aging of the skin. These behaviour statistics were similarly found int he United States, and Europe. Within the study, it was found that the runners were most likely to wear sunglasses for protective clothing, and least likely to use full sleeve clothes. It was also found that facial protection, such as sunscreen on the face, hat, or sunglasses, were more likely to be used that full body protection, such as sunscreen on the entire body, or wearing full sleeves.

Breast Cancer in Women

It is known that physical activity can help reduce the risk of breast cancer. The association between running and risk of breast cancer may vary among women. It is seen that in younger, healthy and toned women, there may be greater risk of breast cancer in those larger breasts. It is seen in previous studies that there may be a relationship of breast cancer with breast volume.

Women who run (or walk for exercise) are seen to be healthier and toned in comparison to other women. THis may affect whether their breast size is a risk factor for mortality. When assessed at different exercise intensity levels, women who ran at a vigorous intensity (≥ 7.5 MET hours/week) were 41% less likely than those who ran at a moderate or light pace (< 7.5 MET hours/week) to be at risk of breast cancer.

In addition, higher circulating levels of estrogen are related to an increased risk of breast cancer. Physical activity helps to lower circulating estrogen, thus lowering the risk of breast cancer. Women with larger breasts and a narrow waist, seen in physically active women, have a much higher estrogen concentration, as opposed to women with a larger waist.

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