2023-10-04 10:23:00
According to Public Health France, approximately 80,000 skin cancers are diagnosed each year in France. While this cancer can affect everyone, there is a slight difference between the two sexes. In its latest figures dating from 2021, the health organization explains: “In France, for the year 2018, the estimated number of new cases of melanoma of the skin was 7,886 among men and 7,627 among women“.
When it comes to deaths, men are also more affected than women. In the same year, skin cancer caused 1,135 deaths among men compared to 840 among women. But what is this difference due to?
Researchers tried to understand this difference between the two sexes. There is one piece of information that stood out: men with baldness were more prone to fatal skin cancers. Although this observation has been made, the exact causes are still unclear.
Thus, researchers from the Queensland Medical Research Institute (QIMR) in Australia wanted to prove this link between baldness and skin cancer, but also explain it. Their results were published on October 3, 2023 in the journal Nature Communications.
Before beginning their work, the researchers already had two hypotheses in mind to explain the link between baldness in men and the risk of fatal skin cancers. The first hypothesis considered was testosterone level. “Testosterone levels are a major factor in male pattern baldness and some studies suggest they may also contribute to this increased risk of skin cancer in people suffering from hair loss“, explains Dr Jue-Sheng Ong, one of the authors of the study.
The second hypothesis would simply be the fact that because of baldness, certain areas of the body (neck and skull) are in direct contact with the sun, whose UV rays promote skin cancer. “The most obvious explanation would be that people suffering from hair loss are more exposed to the sun at the head and neck level“, shared the authors before the study.
Skin cancer: testosterone levels have no impact
To find out which of the two hypotheses was correct, the researchers analyzed genetic data from more than 29,000 cases of melanoma and keratinocyte cancer, available from the landmark QSkin study and the Melanoma Institute Australia and the UK Biobank (largest long-term study in the UK). For their observations, the scientists also incorporated large-scale genetic findings regarding testosterone and hair loss. The aim was to observe whether genes that predispose people to high testosterone levels (baldness being caused by excess male hormones) affect skin cancer.
Researchers have well established a strong link between baldness and skin cancer, thus validating the many previous hypotheses. In contrast, they found no evidence linking high testosterone levels to increased risk of skin cancer. “We found no evidence that testosterone levels play a significant role in the relationship between baldness and skin cancer“, explain the authors.
Baldness: the genes responsible are linked to skin pigmentation
On the other hand, they found that genes linked to hair loss might play a role in skin cancer. “Interestingly, we discovered an overlap between genes responsible for hair loss and genes affecting skin color or pigmentation. Skin color is a known risk factor for skin cancerand these results suggest that pigmentation may also contribute to this increased risk in people with hair loss,” said the study authors.
Exposure to the sun: it remains the main cause of skin cancer in people with baldness
While this discovery regarding the link between skin cancer and the genes responsible for baldness is interesting, experts maintain that the main cause remains exposure to the sun. “The majority of this relationship between baldness and skin cancer is still explained by increased exposure to the sun“, explain the authors.
Indeed, they reached this observation thanks to an in-depth analysis of skin cancers in people suffering from hair loss, classified by anatomical regions. Thus, baldness has been associated with an increased risk of developing skin cancers of the head and neck. In fact, by not being protected by hair, people suffering from baldness are more exposed to the sun. “We set out to find clear answers and, unsurprisingly, it seems that the most sensible explanation is the correct one. Bald men are more susceptible to sun damage and skin cancer because they have less hair protection,” the authors conclude.
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