In life, there are differences between men and women.

In medicine, there are also “gender differences” in some diseases. For example, the incidence and mortality rates of cancer, a disease that causes global health damage and reduced life expectancy, are significantly different between men and women. They “prefer” men to women!

According to the latest global cancer burden data for 2020 released by the International Agency for Research on Cancer (IARC) of the World Health Organization, the age-standardized incidence rate of cancer among men is 222/100,000 person-years, 19% higher than that of women (186/100,000 person-years). The age-standardized mortality rate for men was 120.8/100,000-years, 43% higher than that for women (84.2/100,000-years).

Why are men more likely to develop cancer than women? A recent study published in Cancer, a leading journal of the American Cancer Society (ACS), suggests that men’s greater susceptibility to cancer than women may be related to gender differences rather than just factors such as smoking, drinking, diet, weight and height.

Researchers analyzed data from the NIH-AARP Diet and Health study in the United States, which included 294,100 participants. The participants were between 50 and 71 years old, with an average age of 61; 58.2% (171,274) were men.

Using questionnaires, the researchers tallied basic information about the participants, such as age, gender, ethnicity, and marital status; information about exposure to cancer risk factors, including behavioral factors (e.g., smoking status, alcohol consumption, physical activity), metabolic factors (e.g., body mass index [BMI], diabetes), dietary factors (e.g., intake of grains, fruits, vegetables, meat, coffee, and tea), and height, and family history of cancer, etc.

In addition, during the follow-up period, researchers collected information on the participants’ prevalence of 21 different types of cancer, including lung, pancreatic, colon, rectal, thyroid, gallbladder, liver, non-cardia gastric, gastric cardia, esophageal squamous cell, esophageal adenocarcinoma, skin (excluding basal cell and squamous cell), bladder, and head and neck cancers.

During a mean follow-up period of up to 12 years, a total of 26,693 participants developed new cancers, of which 67.2% (17,951) were men and 32.8% (8,742) were women.

Among men, the five most common new cancers were lung, colon, skin, bladder, and kidney cancers.

Among women, the five most common new cancers were lung, colon, skin, pancreatic, and kidney cancers.

Overall, men have a significantly higher risk of developing cancer than women. Among 21 types of cancers, men had a lower risk than women except for thyroid cancer and gallbladder cancer; 14 cancers had a significantly higher risk than women, which was 1.3-10.8 times higher than women.

Compared with women, men.

had a 45% and 67% lower risk of thyroid cancer and gallbladder cancer, respectively.

did not have a significantly lower or higher risk of anal, lung, pancreatic, colon and small intestine cancers

The risk of developing adenocarcinoma of the esophagus (980%), larynx (253%), gastric cardia (249%), bladder (233%), liver (160%), oropharynx (157%), non-cardia gastric (121%), other biliary tract (99%), kidney (57%), esophageal squamous cell carcinoma (46%), skin (42%), oral cavity (38%), rectum (36% ) and other head and neck cancers (33%) were at significantly higher risk.

In addition, the study results also showed that men are more likely to develop cancer than women, partly, but not entirely, because of behavioral factors, metabolic factors, dietary factors, and cancer risk factors such as height.

Gender differences in cancer risk between men and women were associated with approximately 49.5% of lung cancers, 39.4% of rectal cancers, 33.3% of colon cancers, 23.8% of skin cancers, 19.9% of bladder cancers, 14.1% of other biliary cancers, and 11.2% of esophageal adenocarcinomas, in relation to exposure to these cancer risk factors.

Researchers analyzed that men are more likely to develop cancer than women, and in addition to being more likely to be exposed to cancer risk factors, such as more men having the habit of smoking and drinking alcohol, being more likely to be obese, not exercising, eating an unhealthy diet, and rarely getting vaccinated against HPV (human papilloma virus, which can cause oral cancer), there are also strong relationships with biological differences between the sexes, including physiology, immunology, and genetics, etc., and these differences may play a more important role.

Physiologically, differences in sex steroid hormones, such as progesterone and estrogen, are thought to have a protective effect on women and help reduce their risk of certain types of cancer. In addition, higher levels of testosterone (testosterone), which may promote cell growth, have been associated with an increased risk of malignant melanoma of the skin, prostate cancer and liver cancer in men.

Immunologically, compared to men, women have stronger innate and acquired immune functions, particularly helper T lymphocyte 2 (Th2), which can reduce susceptibility to cancer. For example, women develop stronger immune responses to hepatitis B virus, hepatitis C virus and human papillomavirus, which can help reduce the risk of liver and oral cancer.

Sex differences in cancer risk between men and women may also arise from genetic and epigenetic mechanisms. Females have 2 sex chromosomes of identical size and morphology, called the X chromosome, while males have 2 sex chromosomes, 1 identical to the X chromosome and the other much smaller, called the Y chromosome. And on the X chromosome, there are several tumor suppressor genes. In addition, men lose certain mosaics of the male Y chromosome as they age.

Finally, these factors do not act independently, but interact with each other and, through complex interactions, together contribute to the sex differences in cancer risk.

It is important to note that the mechanisms involved are not yet clear, and more methods, and studies are needed to explore the causes of sex differences in cancer risk in men and women.

The study concludes that cancer is one of the leading causes of impaired human health and longevity, with men having more than twice the risk of developing most cancers than women. Understanding the potential causes of gender differences in cancer risk will not only help mitigate and eventually eliminate gender differences in cancer, but also help achieve precision medicine.

Researchers suggest that measures should be taken in more ways to reduce gender differences in cancer, from cancer risk prediction, primary prevention, cancer screening and secondary prevention, to cancer treatment and patient prognosis management, to better prevent and treat cancer, reduce the risk of developing cancer and improve patient survival.