Comparison of early-onset and later-onset cancer incidence
For early-onset cancers in females, thyroid cancer exhibited the highest number of countries (37 out of 44 countries) with statistically significant positive AAPCs, followed by breast cancer (23 countries), melanoma (19 countries), uterine cancer (17 countries), and colorectal cancer (16 countries) (Figs. 1 and 2; Additional file 1: Table S1). Among the countries with significant positive AAPCs, the range varied from 1.1% (95% CI 0.2–2.1) in Finland to 17.7% (95% CI 15.8–20.0) in China for thyroid cancer, from 0.5% (95% CI 0.2–0.7) in Australia to 5.4% (95% CI 5.1–5.8) in Republic of Korea for breast cancer, 1.3% (95% CI 0.5–2.3) in Austria to 9.1% (95% CI 1.3–17.7) in Malta for melanoma, and 1.4% (95% CI 0.4–2.3) in Finland to 3.8% (95% CI 3.2–4.4) in United Kingdom for colorectal cancer (Additional file 1: Table S1). Among these early-onset cancer types in females with statistically significant positive AAPCs, we observed statistically significantly higher AAPCs in early-onset cancers than in later-onset cancers in the following cancer types: colorectal cancer (6 countries; Canada, USA, France, United Kingdom, Australia, New Zealand), cervical cancer (6 countries; Turkey, the Netherlands, Norway, Sweden, United Kingdom, Australia), pancreatic cancer (5 countries; Republic of Korea, Ecuador, USA, United Kingdom, Australia), and multiple myeloma (5 countries; Republic of Korea, Canada, USA, Austria, United Kingdom) (Fig. 2). These faster increases in early-onset than in later-onset cancers across multiple cancer types, were mainly observed globally, especially in North America, Europe, and Oceania (Additional file 1: Table S2). A sharper increase in early-onset colorectal cancer (AAPC = 2.4%, 95% CI 2.1–2.6) compared to later-onset colorectal cancer (AAPC = −0.1%, 95% CI −0.2 to 0) was observed in the very high-HDI country group (Additional file 1: Table S3).
Magnitude of increases in early-onset cancer incidence. Gallbladder cancer includes gallbladder and extrahepatic bile duct cancers. CNS cancer includes brain and central nervous system (CNS) cancer. Oral cancer includes lip, oral cavity, and pharynx cancers. AAPC average annual percentage change
Comparisons between the early-onset and later-onset cancer incidence trends. Gallbladder cancer includes gallbladder and extrahepatic bile duct cancers. CNS cancer includes brain and central nervous system (CNS) cancer. Oral cancer includes lip, oral cavity, and pharynx cancers. AAPC average annual percentage change
For early-onset cancers in males, thyroid cancer showed the highest number of countries (34 out of 44 countries) with statistically significant positive AAPCs, followed by kidney cancer (22 countries), testis cancer (22 countries), prostate cancer (21 countries), and colorectal cancer (18 countries) (Figs. 1 and 2; Additional file 1: Table S4). Among the countries with significant positive AAPCs, the range for thyroid cancer varied from 1.9% (95% CI 0.7–3.1) in France to 20.7% (95% CI 18.4–22.5) in China. For kidney cancer, the range was from 2.0% (95% CI 1.0–3.0) in Finland to 9.2% (95% CI 3.1–15.3) in Ecuador. Similarly, for testis cancer, the range was from 0.4% (95% CI 0.1–0.8) in USA to 7.5% (95% CI 1.6–13.9) in Kuwait (Additional file 1: Table S4). Among these early-onset cancer types in males with statistically significant positive AAPCs, we observed statistically significantly higher AAPCs in early-onset cancers than in later-onset cancers in the following cancer types: prostate cancer (12 countries; Costa Rica, Czech Republic, Denmark, Estonia, Finland, Ireland, Lithuania, the Netherlands, Norway, Spain, Sweden, Australia), colorectal cancer (8 countries; Israel, Canada, USA, Germany, Sweden, United Kingdom, Australia, New Zealand), and kidney cancer (6 countries; Republic of Korea, USA, Finland, Ireland, United Kingdom, Australia) (Fig. 2). A sharper increase in early-onset colorectal cancer than later-onset colorectal cancer was observed globally, especially in North America, Europe, Oceania (Additional file 1: Table S2). When stratified by the HDI, these steeper increases in early-onset cancers compared with later-onset cancers were mainly observed in the very high-HDI country group (Additional file 1: Table S3), including early-onset colorectal cancer (AAPC = 2.0%, 95% CI 1.7–2.4) compared to later-onset colorectal cancer (AAPC = −0.2%, 95% CI −0.3 to 0), early-onset prostate cancer (AAPC = 2.2%, 95% CI 1.9–2.6) compared to later-onset prostate cancer (AAPC = −0.4%, 95% CI −1.0 to 0.2), and early-onset kidney cancer (AAPC = 3.5%, 95% CI 3.0–3.9) compared to later-onset kidney cancer (AAPC = 2.1%, 95% CI 1.8–2.4).
Detailed data on ASRs and AAPCs in early-onset and later-onset cancer incidence are described in Additional file 1: Tables S1 and S4.
Correlation between obesity prevalence and early-onset cancer incidence
We assessed the correlations between obesity prevalence in younger populations and incidence of early-onset obesity-related cancers in countries with statistically significant positive AAPCs (Additional file 2: Figs. S1–S11). Overall, our results showed strong positive correlations between the increasing obesity prevalence and the rising incidence of early-onset obesity-related cancers in many countries. In females, we observed statistically significant positive correlations for thyroid cancer in 32 countries (China, Israel, Japan, Republic of Korea, Thailand, Turkey, Chile, Colombia, Ecuador, Costa Rica, Canada, USA, Austria, Croatia, Cyprus, Czech Republic, Denmark, Finland, Germany, Ireland, Latvia, Lithuania, Malta, Netherlands, Norway, Poland, Slovenia, Sweden, Switzerland, United Kingdom, Australia, New Zealand), followed by uterine cancer (16 countries; China, India, Japan, Republic of Korea, Thailand, Turkey, Ecuador, Canada, USA, Croatia, Denmark, Estonia, Lithuania, United Kingdom, Australia, New Zealand), kidney cancer (13 countries; Japan, Republic of Korea, Turkey, Canada, USA, Denmark, Germany, Ireland, Netherlands, Norway, Sweden, United Kingdom, Australia), colorectal cancer (11 countries; Japan, Republic of Korea, Thailand, Turkey, Canada, USA, Denmark, Finland, Sweden, United Kingdom, Australia), and multiple myeloma (10 countries; Japan, Republic of Korea, Thailand, Turkey, Canada, USA, Malta, Sweden, United Kingdom, Australia). At a country level, significant positive correlations for many cancer types were observed in several countries, especially in Australia (7 cancer types; thyroid cancer, colorectal cancer, uterine cancer, kidney cancer, pancreatic cancer, multiple myeloma, liver cancer), United Kingdom (7 cancer types; thyroid cancer, colorectal cancer, uterine cancer, kidney cancer, pancreatic cancer, multiple myeloma, liver cancer), Canada (7 cancer types; thyroid cancer, colorectal cancer, uterine cancer, kidney cancer, pancreatic cancer, multiple myeloma, liver cancer), Republic of Korea (7 cancer types; thyroid cancer, colorectal cancer, uterine cancer, kidney cancer, pancreatic cancer, multiple myeloma, ovarian cancer), and USA (6 cancer types; thyroid cancer, colorectal cancer, uterine cancer, kidney cancer, pancreatic cancer, multiple myeloma, stomach cancer). Significant negative correlations were observed in the following cancer types and countries: thyroid cancer (Kuwait, Belarus, and Spain), and pancreatic cancer (Spain), which were reflected in recent decreasing trends in obesity. In males, we observed statistically significant positive correlations for thyroid cancer in 27 countries (China, Israel, Japan, Republic of Korea, Colombia, Ecuador, Costa Rica, Canada, Austria, Belarus, Croatia, Cyprus, Denmark, Finland, Ireland, Italy, Latvia, Lithuania, Netherlands, Norway, Poland, Slovenia, Sweden, Switzerland, United Kingdom, Australia, New Zealand), followed by kidney cancer (20 countries; China, India, Japan, Republic of Korea, Turkey, Ecuador, Canada, USA, Belarus, Denmark, Finland, Ireland, Latvia, Malta, Netherlands, Norway, Sweden, United Kingdom, Australia, New Zealand), colorectal cancer (16 countries; Israel, Republic of Korea, Thailand, Argentina, Canada, USA, Belarus, Denmark, Estonia, Finland, Netherlands, Norway, Sweden, United Kingdom, Australia, New Zealand), multiple myeloma (7 countries; Japan, Republic of Korea, Canada, USA, Lithuania, United Kingdom, Australia), and liver cancer (5 countries; Latvia, Lithuania, Poland, Sweden, United Kingdom). At a country level, significant positive correlations for many cancer types were observed in several countries, including United Kingdom (7 cancer types; thyroid cancer, kidney cancer, colorectal cancer, multiple myeloma, gallbladder cancer, pancreatic cancer, liver cancer), Canada (6 cancer types; thyroid cancer, kidney cancer, colorectal cancer, multiple myeloma, gallbladder cancer, pancreatic cancer), Australia (5 cancer types; thyroid cancer, kidney cancer, colorectal cancer, multiple myeloma, pancreatic cancer), Sweden (5 cancer types; thyroid cancer, kidney cancer, colorectal cancer, gallbladder cancer, liver cancer), Republic of Korea (4 cancer types; thyroid cancer, kidney cancer, colorectal cancer, multiple myeloma).
Comparison of early-onset cancer incidence and early-onset cancer mortality
In females, although many early-onset cancer types exhibited statistically significant positive AAPCs in incidence in various parts of the world, many of them did not show statistically significant positive AAPCs in mortality. Both the incidence and mortality of early-onset cancer showed statistically significant positive AAPCs in the following cancer types and countries: uterine cancer (Japan, Republic of Korea, Ecuador, USA, and United Kingdom), colorectal cancer (Canada, USA, and United Kingdom), liver cancer (Canada, United Kingdom), breast cancer (Ecuador), cervical cancer (Japan), and thyroid cancer (Slovenia) (Fig. 3; Additional file 2: Fig. S12). For uterine cancer, the range of statistically significant positive AAPCs in early-onset cancer mortality varied from 3.1% (95% CI 1.5–4.8) in the Philippines to 19.7% (95% CI 10.6–29.3) in Ecuador. For early-onset colorectal cancer mortality, the range was 0.5% (95% CI 0.1–1.0) in the USA to 3.3% (95% CI 2.7–4.0) in the Philippines (Additional file 1: Table S5).
Comparisons between the early-onset cancer incidence trend and the early-onset cancer mortality trend. Gallbladder cancer includes gallbladder and extrahepatic bile duct cancers. CNS cancer includes brain and central nervous system (CNS) cancer. Oral cancer includes lip, oral cavity, and pharynx cancers. AAPC average annual percentage change
Similarly, in males, we did not observe statistically significant positive AAPCs in the mortality of many early-onset cancer types. Both the incidence and mortality of early-onset cancer showed statistically significant positive AAPCs in the following cancer types and countries: colorectal cancer (Argentina, Canada, USA, Netherlands, and United Kingdom), testis cancer (Colombia and Croatia), liver cancer (Lithuania), gallbladder cancer (Sweden), and thyroid cancer (Sweden) (Fig. 3; Additional file 2: Fig. S13). For early-onset colorectal cancer mortality, statistically significant positive AAPC ranged from 0.6% (95% CI 0.2–0.9) in the USA to 3.6% (95% CI 1.5–5.8) in Chile (Additional file 1: Table S6).
To investigate the more recent trend of early-onset cancer mortality, we extended our mortality analysis after 2017 for cancer types and countries with statistically significant positive AAPCs in both incidence and mortality of early-onset cancers from 2000 to 2023 (or 2021/2022 depending on data availability). Although we did not observe an apparent spike after 2017 in many countries, we observed continued increases in the mortality of certain cancer types, such as uterine cancer [Japan (AAPC = 2.8%, 95% CI 1.7–4.2), Republic of Korea (AAPC = 6.3%, 95% CI 4.4–8.6), United Kingdom (AAPC = 4.0%, 95% CI 2.5–5.7), USA (AAPC = 3.8%, 95% CI 2.6–4.9), and Ecuador (AAPC = 12.8%, 95% CI 4.6–21.8)] in females and colorectal cancer [Argentina (AAPC = 1.0%, 95% CI 0.6–1.4), Canada (AAPC = 0.9%, 95% CI 0.3–1.6), United Kingdom (AAPC = 1.2%, 95% CI 0.6–1.7), and USA (AAPC = 0.5%, 95% CI 0.3–0.9)] in males (Additional file 1: Table S7; Additional file 2: Figs. S14 and S15).