Epidemiology of Stomach Cancer: A Global Perspective
Stomach cancer, a condition often marked by high geographic variability, showcases stark contrasts in incidence and mortality rates across different regions. In 2020, the world saw major differences in where stomach cancer took the most toll:
Eastern Asia took the lead with the highest incidence rate at 22.4 cases per 100,000 people, notably in countries like Japan, Mongolia, and the Republic of Korea.
Central and Eastern Europe followed, with 11.3 cases per 100,000 people.
Regions like South America, Polynesia, and Western Asia registered about 8.6 cases per 100,000 people.
The lowest incidence rates were in Southern Africa (3.3 per 100,000 people), emphasizing regional disparities.
Where Is Stomach Cancer Most Common?
A deeper dive into the statistics reveals that Asia bears the heaviest burden of stomach cancer. More than 75% (819,944) of all cases globally occurred in Asia. Despite the overwhelming presence in more developed regions, Micronesia/Polynesia recorded the least cases.
The Male-Female Divide
Globally, the incidence rates in men were roughly 2 to 3 times higher than in women. For instance:
Males in Eastern Asia exhibited rates as high as 32.5 per 100,000.
Conversely, women in Southern Africa had a much lower incidence rate, about 2.4 per 100,000.
Sexual Disparities and Global Patterns
Male Incidence: Males in Japan recorded the highest at 48.1 per 100,000, while Mozambique had the lowest at just 1.0 per 100,000.
Female Incidence: Women in Mongolia saw the highest rate at 20.7 per 100,000, with Mozambique again having one of the lowest rates.
These patterns are not entirely predictable. Even within high-risk areas such as East Asia, countries like Sri Lanka and Thailand have relatively lower rates. Surprisingly, populations like Koreans and Japanese residing in the United States exhibit higher incidence rates, a phenomenon that may point to environmental and lifestyle factors influencing cancer risk.
Racial and Ethnic Differences in the U.S.
Within the United States, a country with overall lower stomach cancer rates:
Black men showed the highest incidence, followed by Asian/Pacific Islanders.
Hispanic women had the highest rates, with black women following closely.
Among Indigenous populations, such as the Siberians, Mapuche in Chile, and Alaskan Inuit, the incidence of stomach cancer was disproportionately high, signaling a need for further study into cultural, dietary, and genetic influences on cancer risk.
Risk Factors: Environmental and Lifestyle Influences
The global variation in stomach cancer is largely attributed to differences in exposure to environmental and lifestyle risk factors:
Helicobacter pylori infection is the most significant risk factor, showing a high correlation with the prevalence of stomach cancer. In regions with high rates of infection, such as South Africa, China, and Mexico, stomach cancer rates are often elevated.
Tobacco smoking plays a crucial role, particularly in East Asia, where smoking rates are high.
Dietary factors also contribute, with high salt intake and low consumption of fresh fruits and vegetables being common in high-risk areas.
Interestingly, despite high H. pylori infection rates in certain regions like Africa and South Asia, the incidence of stomach cancer is lower compared to East Asia. This could be due to genetic variations in the H. pylori strains, with East Asia predominated by a more virulent vacA m1 genotype.
Aging and Gender Differences in Incidence
Stomach cancer risk increases with age, with the highest incidence seen in individuals aged 75 and older. Additionally, the higher male incidence is attributed to the predominance of intestinal adenocarcinoma in older populations, while diffuse adenocarcinoma is more common in younger women.
Trends and Shifting Mortality Rates
Globally, stomach cancer mortality followed a similar pattern, with Eastern Asia recording the highest death rates. In Mongolia, mortality reached 24.6 per 100,000 people. In contrast, countries like Mozambique had death rates as low as 0.7 per 100,000.
Factors Influencing Mortality
In developed regions like Japan, improvements in gastric cancer screening and lifestyle changes have led to a decrease in mortality. Reductions in salt consumption, improved food storage, and the eradication of H. pylori have contributed to the decline.
Aging and the prevalence of diffuse adenocarcinoma, which is harder to detect early, contribute to the continuing high mortality rates, especially in developing nations.
Global Geographic Disparities in Gastric Cancer
The geographic variability of gastric cancer incidence and mortality is stark:
Low-risk populations, such as those in Northern Europe, Australia, and some parts of Africa, contrast sharply with the high-risk regions of East Asia, where the disease remains a leading cause of cancer death.
Cardia cancer, a subtype of gastric cancer, appears more frequently in countries with lower overall incidence, such as the United States and Denmark, adding another layer of complexity to global patterns.
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