Global statistics and risk factors of neoplasms in the elderly, and the impact of aging on neoplasms from 1990 to 2021.

Introduction
Neoplasms/tumors, which refer to abnormal and excessive proliferations of cells forming new growths beyond normal physiological needs and persisting to grow, are categorized into benign tumors (not cancer) and malignant tumors (also termed cancer)[1–3]. Among them, cancers pose a major and escalating global health challenge, particularly affecting the elderly population disproportionately[4]. This demographic group bears a heavier burden of cancer[4], with aging being a major factor influencing cancer incidence and mortality rates[5,6]. In 2020, 64% of the 19.3 million new cancer cases worldwide occurred in individuals aged 65 and older, accounting for 71.3% of cancer-related deaths[6]. Moreover, the World Health Organization (WHO) highlights that population aging is accelerating rapidly, presenting a major challenge for all countries to ensure that their health and social systems are adequately prepared to address this demographic shift[7]. With the growth of the aging population, the burden of noncommunicable diseases, such as neoplasms that typically occur in the elderly, is also increasing[8]. All countries will face significant challenges[9]; without effective measures, it is projected that the incidence and mortality of cancer among this population will continue to rise[10], leading to a cascade of social, economic, and ethical issues[9,11,12]. The negative impacts of cancer on the elderly population, including a range of physiological damages, psychological issues, and lack of social support, cannot be overlooked[13]. Due to the decline in organ function, the elderly often have poorer tolerance and higher risks of treatment toxicity throughout the entire process from cancer onset to treatment[14], and they are accompanied by higher rates of depression and anxiety[15], facing a series of social isolation issues[12]. At the same time, globally, the incidence and mortality of cancer, as well as epidemiological data and burdens, vary greatly across regions: Asia accounts for about 50% of all cancer cases and has the highest number of cancer-related deaths. In comparison, Europe accounts for approximately 25% of global cancer cases[16]. A statistical report shows that in 2018, the incidence rate of cancer among adults aged 80 and above worldwide was 6% in Africa, the highest in Japan (31%), and the lowest in the Solomon Islands (2%)[10]. Based on the extensive data presented above, it is evident that due to the substantial proportion and significant impact of cancer, relevant epidemiological data primarily focus on cancer. Currently, there are no reports that comprehensively document the global burden of neoplasms, including cancers, among the elderly population aged 55 and above. However, including benign and borderline tumors in these considerations is equally important. There is an urgent need for targeted intervention measures and cohesive global strategies to alleviate the impact of neoplasms on the elderly population.
Therefore, the purpose of this analysis is to characterize the global, regional (21 regions), and national (204 countries and territories) trends in the incidence and mortality of neoplasms, as well as the trends in disability-adjusted life years (DALYs), incorporating data on gender, age group, and the Socio-demographic Index (SDI). The 2021 Global Burden of Disease (GBD) study, led by the University of Washington, conducted an in-depth assessment of 371 diseases and injuries related to health hazards and 288 causes of death and life expectancy decomposition, covering 204 countries and territories. Over 11 500 collaborators from 164 countries supported it, systematically evaluating global health status and disease burden through extensive data provision, review, and analysis[17–20]. Thus, the GBD study is a reliable tool for understanding and assessing the current burden of neoplasms. Furthermore, with the rapid development of AI, there have been concerns about its use in academic writing. We would like to assure you that our manuscript strictly adheres to the Transparency In The reporting of Artificial Intelligence Guidelines 2025 to ensure the integrity and quality of our research and writing[21].
Since the update of GBD 2021, there has been no comprehensive systematic report on the epidemiology of neoplasms in the elderly population, trends, risk factors, and the impact of aging. In this study, we utilized the GBD statistical modeling system to describe the disease burden of overall neoplasms and 34 types of neoplasms from 1990 to 2021, including epidemiological data focusing on age and gender distribution, temporal trends, risk factors, and the impact of aging. This analysis helps clinicians, epidemiologists, and health policymakers comprehensively understand the disease burden of neoplasms, further optimize the allocation of medical resources, develop more effective public health strategies, and alleviate the social burden of neoplasms.
HIGHLIGHTS
Neoplasm incidence hit 2281.4 per 100 000 in 2021, with varying burdens observed.

Skin neoplasms rose in incidence, while stomach cancer and Hodgkin lymphoma declined in mortality and DALYs.

Gastrointestinal and respiratory neoplasms are greatly affected by aging.

Smoking stayed the top risk factor, with drug use as the fastest-growing risk.

This study supplies multiple insights into neoplasm, helping shape elderly health care strategies.

Methods

Data source
The present study extracted global incidence, mortality, and DALYs (one DALY represents the loss of 1 year of full health due to premature death or disability), along with their 95% uncertainty intervals (UI), spanning from 1990 to 2021 from the GBD database (https://vizhub.healthdata.org/gbd-results/). Data on sex, age groups, population, and SDI were also included for comprehensive analysis.

SDI analysis
The SDI was employed as a metric to assess the socioeconomic status of countries, with a higher score indicating more robust socioeconomic development. Derived from national-level indicators encompassing per capita income, average educational attainment, and total fertility rate, the SDI assumes values ranging from 0 to 1. Countries were stratified into five quintiles based on the GBD studies: high SDI (>0.81), high-middle SDI (0.70–0.81), middle SDI (0.61–0.69), low-middle SDI (0.46–0.60), and low SDI (<0.46)[17–20]. To examine the correlation between SDI and the burden of neoplasms, locally estimated scatterplot smoothing (loess) models were applied, utilizing the geo-smooth function within the ggplot2 package. This analysis fitted the relationship across global data, 21 regions, and 204 countries and territories.

Decomposition analysis
To quantify the drivers of changes in neoplasm patient numbers, we estimated the relative contributions of aging, population, and epidemiological factors using the Das Gupta method for decomposition analysis[22], which employs algebraic decomposition techniques to disaggregate the overall change into standardized effects for each factor, thereby identifying the contribution of each component. We defined aging as the shift in population distribution toward older age groups, population growth as the overall expansion of the population, and epidemiological changes as variations in neoplasm rates due to risk factors and health care improvements. Using data from the GBD database, we calculated the standardized effect of each factor. Taking the DALYs as an example, the specific calculation steps are as follows: The number of DALYs for each location can be calculated as , where DALYay,py,ey represent the DALYs based on factors such as age structure, population, and DALY rates for a specific year y. ai,y represents the population proportion of age group i among n age groups in year y; py signifies the total population in the given year y; eiy indicates the DALY rate for a specific age category i in year y. From 1990 to 2021, the contribution of each factor to the changes in DALYs is defined by the impact of one factor’s variation while keeping the other factors constant.

Statistics analysis
55+ years rates were expressed as predicted values per 100 000 population, including their 95% UI. All analytical procedures and graphical representations were executed using the statistical software R (version 4.4.1).

Results

Global level
In 2021, the global number of new cases was 33 901 264 (29 974 022, 38 871 301). The rate was 2281.4 (2017.11, 2615.86). From 1990 to 2021, it increased by 0.16 (0.11, 0.2). The number of deaths was 8 192 572 (7 485 652, 8 787 578). The mortality rate was 551.32 (503.75, 591.36). From 1990 to 2021, it decreased by −0.16 (−0.21, −0.09). Global DALYs were 170 885 851 (158 291 984, 183 127 418), with a rate of 11 499.83 (10 652.32, 12 323.63). From 1990 to 2021, it decreased by −0.21 (−0.27, −0.15) (Table 1).

Regional level
In 2021, at the SDI level, the incidence rate was highest in High SDI regions, at 5203.32 (4607.04, 5963.9). This rate decreased with decreasing SDI, with low SDI at 820.84 (685.93, 988.67). Geographically, the high-income North American region had the highest rate at 10 630.78 (9325.06, 12 310.36) (Table 1, Supplementary Digital Content, Table S1, available at: http://links.lww.com/JS9/E879, and Figure 1A). From 1990 to 2021, the fastest increase was in High SDI regions, with an upward trend of 0.47 (0.42, 0.53). Geographically, high-income North America showed the most significant upward trend at 0.84 (0.73, 0.94) (Table 1, Supplementary Digital Content, Table S1, available at: http://links.lww.com/JS9/E879, and Figure 1B).

In 2021, at the SDI level, the mortality rate was highest in high SDI regions at 719.96 (644.08, 761.21). Geographically, the Central Europe region had the highest rate at 857.25 (791.51, 911.53) (Table 1, Supplementary Digital Content, Table S1, available at: http://links.lww.com/JS9/E879, and Figure 1C). From 1990 to 2021, at the SDI level, there was an overall downward trend, with only low-middle SDI showing an upward trend of 0.09 (−0.01, 0.2). Geographically, Southern Sub-Saharan Africa showed the most significant upward trend at 0.23 (0.12, 0.37) (Table 1, Supplementary Digital Content, Table S1, available at: http://links.lww.com/JS9/E879, and Figure 1D).
In 2021, at the SDI level, the DALY rates were highest in high-middle SDI regions at 13 653.8 (12 416.02, 15 045.86). Geographically, the Central Europe region had the highest DALY rates at 17 663.93 (16 414.69, 18 748) (Table 1, Supplementary Digital Content, Table S1, available at: http://links.lww.com/JS9/E879, and Figures 1D and E). From 1990 to 2021, the fastest increase was in High-middle SDI regions, with an upward trend of 0.05 (−0.05, 0.16). Geographically, Southern Sub-Saharan Africa showed the most significant upward trend at 0.27 (0.16, 0.42) (Table 1, Supplementary Digital Content, Table S1, available at: http://links.lww.com/JS9/E879, and Figure 1F).

National and territorial level
In 2021, the United States had the highest incidence cases at 11 364 627 (9 981 484, 13 113 289). The United States also had the highest incidence rate at 11 336.54 (9956.82, 13 080.88). From 1990 to 2021, the fastest increase was also in the United States, with an upward trend of 0.93 (0.81, 1.05) (Supplementary Digital Content, Table S2, available at: http://links.lww.com/JS9/E880, and Figures 1A and B).
In 2021, China had the highest number of deaths at 2 366 692 (1 968 146, 2 818 667). Monaco had the highest mortality rate at 1219.55 (1014.31, 1426.91). From 1990 to 2021, the fastest increase was in Lesotho, with an upward trend of 0.66 (0.24, 1.21) (Supplementary Digital Content, Table S2, available at: http://links.lww.com/JS9/E880, and Figures 1C and D).
In 2021, China had the highest number of DALYs at 50 453 552 (41 826 931, 60 204 069). Monaco had the highest DALY rate at 22 338.37 (18 865.96, 26 176.2). From 1990 to 2021, the fastest increase was in Lesotho, with an upward trend of 0.78 (0.31, 1.4) (Supplementary Digital Content, Table S2, available at: http://links.lww.com/JS9/E880, and Figures 1E and F).

Age, sex, and subtype analysis
In 2021, when examining incidence, mortality, and DALYs rates, the highest rates for females were observed in the 95+ age group, while for males, the highest rates were in the 90–94 age group. In terms of numbers, the incidence was highest among females aged 55–59 and among males aged 65–69. For deaths and DALYs, the highest numbers were observed in both sexes aged 70–74. However, the number of DALYs for females aged 55–69 remained relatively stable (Fig. 2, Supplementary Digital Content, Figure S1, available at: http://links.lww.com/JS9/E893, and Supplemental Digital Content Table S3, available at http://links.lww.com/JS9/E881).

In terms of proportions, other neoplasms had the highest proportion within newly developed neoplasms, which decreased with age. In contrast, the proportion of non-melanoma skin cancer (NMSC) increased with age. Among the other major cancers, breast cancer in females, bladder cancer and prostate cancer in males, and colon and rectum cancer in both sexes generally increased with age. In terms of deaths and DALYs caused, prostate cancer and bladder cancer in males and colon and rectum cancer in both sexes showed a rapid increase with age. Esophageal cancer in males, however, decreased in proportion with age.
Tracheal, bronchus, and lung cancer in both sexes initially increased and then decreased, with the highest proportion observed in the 70–74 age group. Breast cancer first decreased and then increased, with the highest proportion in the 55–59 age group (Fig. 2 and Supplementary Digital Content, Table S4, available at: http://links.lww.com/JS9/E882).
From 1990 to 2021, for neoplasms overall, the incidence, mortality, and DALY rates increased the most in the 95+ age group for both sexes. Specifically, among the aforementioned three, the rates for liver cancer in both sexes showed the highest increase in the 95+ years age group, with increases of 12.79, 12.48, and 12.18 in males; and 10.86, 10.41, and 10.18 in females (Supplementary Digital Content, Table S3, available at: http://links.lww.com/JS9/E8814).

Overall temporal trends
The incidence rate has been increasing year by year. Notably, from 2000 to 2005, NMSC saw a significant rise, with the incidence rate of NMSC increasing by 0.82 from 1990 to 2021. Neuroblastoma and other peripheral nervous cell tumors had the highest increase among neoplasms, with an increase of 0.85. Additionally, malignant skin melanoma ranked third with an increase of 0.4. Skin neoplasms occupied two of the top three spots in terms of growth.
Mortality and DALY rates have been decreasing year by year. Among the cancers with larger proportions, Stomach cancer showed the greatest decrease with rates of −0.45 and −0.5. Hodgkin lymphoma had the largest decrease with rates of −0.49 and −0.51. Moreover, in terms of quantity, incidence, deaths, and DALYs have all generally increased over time (Supplementary Digital Content, Figure S2, available at: http://links.lww.com/JS9/E893, and Supplementary Digital Content Table S5, available at: http://links.lww.com/JS9/E883).
Neuroblastoma and other peripheral nervous cell tumors also had the fastest-growing mortality and DALYs rates among neoplasms, with increases of 0.67 and 0.61, respectively (Fig. 3 and Supplementary Digital Content, Table S5, available at: http://links.lww.com/JS9/E883).

However, high SDI and high-income North America had the highest incidence rates and the greatest increase in these rates. The mortality rate gradually decreased, dropping from the second to the seventh position from 1990 to 2021. The DALY rate declined even more, falling from first to eighth. In contrast, Central Asia’s mortality rate and DALYs rate increased compared to other high-ranking regions. The mortality rate and DALYs rate rose from the sixth and fifth to the first position and were significantly higher than the second position. (Fig. 3)

Regions and subtype analysis
The incidence rate is consistent with the conclusions drawn from Figure 2. High-income North America is significantly higher than other regions, particularly with a high proportion of NMSC. Breast cancer, colon and rectum cancer, thyroid cancer, tracheal, bronchus, lung cancer, and uterine cancer show an overall increasing trend from low SDI to high-middle SDI. However, their proportions decline significantly in high SDI regions. Cervical cancer, on the other hand, clearly decreases with the rise in SDI. For mortality rate and DALYs rate, cervical cancer increases noticeably with fewer SDI resources. However, colon and rectum cancer proportion increases with higher SDI, and tracheal, bronchus, and lung cancer also increase with higher SDI, but a decline is observed in males in high SDI regions (Supplementary Digital Content, Figure S3, available at: http://links.lww.com/JS9/E893, and Supplementary Digital Content Table S5, available at: http://links.lww.com/JS9/E883). In terms of quantity, high-income North America has the highest incidence, while East Asia has the highest deaths and DALYs (Supplementary Digital Content, Figure S4, available at: http://links.lww.com/JS9/E893, and Supplementary Digital Content Table S5, available at: http://links.lww.com/JS9/E883).
From 1990 to 2021, in terms of change increases, East Asia’s NMSC incidence rate increased the most with 8.78. At the country and regional level, Georgia’s soft tissue and other extraosseous saw the greatest increase with 48.83. The mortality and DALY rate increased the most for the Caribbean’s testicular cancer with 3.42 and 3.36, respectively. At the country and regional level, the mortality rate increased the most in Georgia’s other neoplasms with 275.87, and the DALYs increased the most for Georgia’s soft tissue and other extraosseous with 43.59 (Supplementary Digital Content, Tables S5, available at: http://links.lww.com/JS9/E883, and S6, available at: http://links.lww.com/JS9/E884).

Decomposition analysis
Globally, among the 34 neoplasms, when considering the changes in deaths, the cancer with the largest proportion and the main reason attributed to aging is stomach cancer in both sexes; in the changes in DALYs, it is tracheal, bronchus, and lung cancer in males and bladder cancer in females. For incidence changes, stomach cancer in males, larynx cancer in males, esophageal cancer in males, gallbladder and biliary tract cancer in females, tracheal, bronchus, and lung cancer in males, mesothelioma in males, and bladder cancer in both genders are the cancers with the largest proportion and the main reason attributed to aging. (Figure 4 and Supplementary Digital Content, Table S7, available at: http://links.lww.com/JS9/F125).

In high SDI regions, the cancers with the largest proportion and the main reason attributed to aging are as follows: for incidence changes, larynx cancer in males and ovarian cancer in females; for death changes, gallbladder and biliary tract cancer in females and nasopharynx cancer in males; and for DALYs changes, larynx cancer in females and leukemia in males (Supplementary Digital Content, Figure S5, available at: http://links.lww.com/JS9/E893, and Supplementary Digital Content Table S8, available at: http://links.lww.com/JS9/E886).
In high-middle SDI regions, the cancers with the largest proportion and the main reason attributed to aging are as follows: for incidence changes, larynx cancer in males and esophageal cancer in females; for death changes, stomach cancer in males and esophageal cancer in females; and for DALYs changes, gallbladder and biliary tract cancer in females and esophageal cancer in males (Supplementary Digital Content, Figure S6, available at: http://links.lww.com/JS9/E893, and Supplementary Digital Content Table S9, available at: http://links.lww.com/JS9/E887).
In middle SDI regions, the cancers with the largest proportion and the main reason attributed to aging are as follows: for incidence changes, nasopharynx cancer in females and stomach cancer in males; for death changes, esophageal cancer in females and nasopharynx cancer in males; and for DALYs changes, nasopharynx cancer in males and larynx cancer in females (Supplementary Digital Content, Figure S7, available at: http://links.lww.com/JS9/E893, and Supplementary Digital Content Table S10, available at: http://links.lww.com/JS9/E888).
In low-middle and low SDI regions, the primary reason for the increase in incidence, deaths, and DALYs is population growth (Supplementary Digital Content, Figures S8, available at: http://links.lww.com/JS9/E893, and S9, available at: http://links.lww.com/JS9/E893, and Tables S11, available at: http://links.lww.com/JS9/E889, and S12, available at: http://links.lww.com/JS9/E890).
Overall, the cancers most affected by aging include stomach cancer, gallbladder and biliary tract cancer, nasopharynx cancer, larynx cancer, and esophageal cancer. Additionally, tracheal, bronchus, and lung cancer, bladder cancer, ovarian cancer, and leukemia are also significantly impacted by aging.
Regarding regional changes, the main pattern is that the impact of aging gradually increases with the rise in SDI (Supplementary Digital Content, Figure S10, available at: http://links.lww.com/JS9/E893, and Supplementary Digital Content Table S13, available at: http://links.lww.com/JS9/E891). In specific regions, the regions with the largest proportion and the main reason attributed to aging are as follows: for incidence changes, Eastern Europe in both sexes; for death changes, Eastern Europe in females and Western Europe in males; and for DALYs changes, Western Europe in both sexes. The focus is mainly on Europe and other regions significantly impacted by aging, including Central Europe, High-income Asia Pacific, High-income North America, and East Asia (Supplementary Digital Content, Figure S11, available at: http://links.lww.com/JS9/E893, and Supplementary Digital Content Table S14, available at: http://links.lww.com/JS9/E892).

Risk factors analysis
Smoking remains the most significant risk factor in 2021, showing an increase followed by a decrease with the rise in SDI, peaking in the high-middle SDI region. Additionally, high fasting plasma glucose, high body mass index, alcohol use, ambient particulate matter pollution, occupational exposure to asbestos, a diet high in red meat, and unsafe sex are also important causes, each contributing more than 20%. Among dietary factors such as high fasting plasma glucose, high body mass index, alcohol use, and a diet high in red meat, there is a general trend of increasing proportion with the increase in SDI. On the environmental front, occupational exposure to asbestos shows a significant increase in proportion with the rise in SDI; however, environmental factors like household air pollution from solid fuels show a significant decrease in proportion as SDI increases. Ambient particulate matter pollution follows a similar trend to smoking, increasing first and then decreasing with the rise in SDI, peaking in the high-middle SDI region. Additionally, unsafe sex shows an increase in proportion as SDI decreases (Fig. 5).

Regarding the changes in proportions from 1990 to 2021, household air pollution from solid fuels has decreased the most, and diet low in vegetables has also significantly decreased; both have seen a reduction of over 50%. The most significant cause, smoking, has also seen a global decrease of over 10%. Among the increases from 1990 to 2021, drug use has grown the fastest, with an increase of over 100%, and in high SDI regions, the increase has exceeded 200%. Other factors with a significant proportion and rapid growth include high fasting plasma glucose and high body mass index, with the former growing by over 60% and the latter by over 40% (Fig. 5).

Discussion
This study presents the first comprehensive and up-to-date assessment of the global burden of neoplasms, risk factors, and the impact of aging on individuals aged 55 and above by integrating a vast array of data from the GBD research. Our research updates and expands the epidemiological evidence regarding the neoplasm burden in this population, providing a detailed profile and new insights. We confirm the substantial burden of neoplasms in the elderly and identify an increasing trend in incidence rates, while the decline in mortality rates has slowed. Additionally, our analysis reveals the impact of aging on neoplasms and significant variations in trends, which are based on age, gender, geographical location, and SDI. The findings underscore the need for targeted health policies and interventions tailored to the specific needs of the aging population.

Overall trends
We comprehensively analyzed the global neoplasm burden among individuals aged 55 and above from 1990 to 2021. The results indicate a significant increase in global neoplasms’ incidence rate, rising from 1973.36 in 1990 to 2281.4 in 2021, with an increase of 0.16 (0.11–0.2). The current study shows that as age increases, neoplasms become a comorbidity of aging, with the frequency of neoplasms in the elderly biosphere steadily increasing[23]. Reports from the WHO have revealed that the world is currently on a trajectory toward an aging population, with the pace of population aging far exceeding that of the past[7].
Despite the increase in incidence, the mortality and DALYs have declined. The mortality dropped from 652.65 in 1990 to 551.32 in 2021, with a change of −0.16 (−0.21 to −0.09). Similarly, the rate of DALYs has gradually decreased over the past 30 years, with a rate change of −0.21 (−0.27 to −0.15). A report indicates that mortality rates for neoplasm types common in the elderly, such as prostate cancer, breast cancer, lung cancer, and colorectal cancer, are declining[24]. It suggests that neoplasm management and survival rates have improved during the study period, possibly due to updated treatment guidelines, enriched medical resources, advancements in therapeutic technology, increased public health awareness, and the global promotion of early diagnosis[24,25].

Impact of aging on neoplasms epidemiology data
The rates of incidence, mortality, and DALYs of neoplasms have complex relationships with SDI, aging, and population growth. Our study results are consistent with established epidemiological data, revealing that the demographic profile of neoplasm patients is increasingly shifting toward the elderly population[6,23,26]. Moreover, as SDI increases, the impact of aging on neoplasms becomes more pronounced, particularly in high-income North American and European regions. Previous studies have established that common neoplasms such as lung, breast, and prostate cancer are increasing among individuals aged 55 and above[6,24]. Our analysis confirmed this result and found that the incidence of common neoplasms closely associated with aging, such as gastric cancer, gallbladder and biliary tract cancer, and nasopharyngeal cancer, shows the most significant increasing trends among individuals aged 55 and above. In these high SDI countries, life expectancy is often higher than in medium and low SDI countries[27], indicating a more pronounced trend toward an aging society. Previous studies have found that as age increases, the human systemic environment changes[23,28]: increased genomic instability in cells, formation of abnormal proteins, telomere attrition, increased inflammation[29], and cellular senescence, all contributing to the high neoplasms’ incidence in high SDI countries due to the large number of elderly individuals. However, globally, population growth is the primary cause of increased incidence among 34 types of neoplasms. In low and low-middle SDI regions, population growth is also the main driver of increased incidence, mortality, and DALY rates. Our results align with a report in another article, indicating that middle and low SDI countries and regions contribute a larger share of the global population. However, these areas have relatively lower incidence rates, and the total number of neoplasm patients increases with the growth of their substantial population sizes[30].

Regional disparities
Additionally, our study confirms significant SDI-related health inequalities in the neoplasms burden among individuals aged 55 and above, with higher SDI countries and regions experiencing faster growth and higher incidence rates. In these high SDI countries and regions, such as high-income North America and the United States, the high incidence rates can be attributed to several factors, including differences in genetic susceptibility and exposure to risk factors, disparities in detection and diagnostic capabilities, implementation of prevention and public health measures, and incomplete data collection and reporting mechanisms in low SDI settings[25]. High SDI regions typically have advanced early detection technologies and substantial health care investments; for instance, in 2017, the estimated health care costs related to prostate cancer in Europe alone were 5.8 billion euros[31]. Furthermore, higher economic levels, personal income, lifestyle changes, and many obese individuals reported in these regions[32] could also lead to the observed outcomes. Concurrently, in our study, lung, breast, and colorectal cancers, which are often associated with lifestyle and environmental factors, were identified as the main contributors to the higher incidence rates in high and high-middle SDI countries. Consistent with GBD studies, our results show that the burden of lung and breast cancer is significantly greater in countries with high and very high SDI, with incidence rates several times higher than in low and medium SDI countries[17].
Although the analysis shows an overall downward trend in global neoplasms mortality rates, in most low SDI countries, the mortality rates for neoplasms in the elderly are increasing. Geographically, the most significant increase is observed in Southern Sub-Saharan Africa. It is unexpected, given the disproportionately low incidence rates in low SDI countries. However, the rise in mortality rates reflects not only differences in incidence but also variations in neoplasm spectra, early diagnosis, availability of health care, and other factors. Consistent with previous epidemiological data, neoplasms in low SDI countries are more likely to be fatal, while neoplasms with better prognoses are more common in high SDI countries[25]. In addition to differences in the distribution of neoplasms types, variations in mortality rates within the same type of neoplasms also contribute to the higher observed neoplasms mortality rates in low SDI countries[17]. For many neoplasms, such as lung, breast, and colorectal, mortality rates can be reduced through proactive prevention and early intervention, and we observe a stronger correlation between mortality rates and SDI. Previous reports have also shown this conclusion: there is a bell-shaped curve relationship between neoplasms-related DALYs and SDI, with the greatest impact in medium SDI countries[33]. It is likely that changes in lifestyle and environmental factors during their socioeconomic development increase neoplasm risk, while health care resources and neoplasm prevention measures in these countries may be insufficient to address the challenges posed by aging[33]. Additionally, we find the highest mortality rates in high SDI regions, such as central Europe, which may be associated with high incidence rates, large population sizes, a greater number of elderly individuals, complex social divisions of labor, and exposure to pollutants. These findings collectively support the opportunities and importance of improving health care systems to reduce neoplasm mortality rates in low SDI countries[34].

Risk analysis
Although many elderly neoplasms are not strongly influenced by behavioral risk factors such as tobacco, alcohol, or nutrition, they may act synergistically with other factors[34]. Our analysis indicates that in 2021, smoking remains the primary risk factor for neoplasms, with the highest impact in middle and high SDI regions. The tar and nicotine contained in cigarettes[35] are carcinogenic substances that can affect DNA replication in cells, leading to genetic mutations and increasing the risk of neoplasms[36]. Other significant risk factors include high fasting blood glucose, high body mass index, alcohol consumption, environmental particulate matter pollution, occupational exposure to asbestos, and drug use. High fasting blood glucose is associated with insulin resistance, which often accompanies cell proliferation and inflammation, potentially increasing the risk of colorectal and pancreatic neoplasms[37]; alcohol consumption is related to various tumors such as oral, laryngeal, esophageal, and liver neoplasms, with its metabolic products potentially causing DNA damage, harming cells, and promoting tumors[38]. Environmental particulate matter pollution, particularly PM2.5, is associated with an increased risk of lung and other respiratory neoplasms. These particles can cause oxidative stress and inflammatory responses, leading to DNA damage and genetic mutations[39]. Occupational exposure to asbestos is a known risk factor for lung cancer and mesothelioma. Asbestos fibers can cause chronic inflammation and fibrosis, leading to cell proliferation and genetic mutations[40,41]. Additionally, the rapidly growing risk factor of drug use deserves attention; while some medications play a key role in monitoring and eliminating early tumor cells[42], they can also increase the risk of neoplasms in the elderly due to immune suppression, hormonal effects, and metabolic changes[43]. Notably, current digital adherence interventions can considerably enhance compliance among elderly cancer patients and effectively alleviate the issue of irrational medication use[44]. Meanwhile, nutritional monitoring plays a vital role in improving treatment outcomes and quality of life and may become a key strategy for addressing medication-related problems in patients[45]. In high SDI regions, these factors highlight the multifaceted nature of neoplasms risk in the elderly population and indicate the necessity of a multifaceted prevention approach that addresses lifestyle factors, as well as environmental and occupational exposures.

Limitation
In this study, we first integrated the latest neoplasms data from GBD 2021 to assess the global neoplasms burden in individuals aged 55 and above. While the current iteration of GBD 2021 provides more accurate and reliable estimates than previous data, it is important to acknowledge significant limitations. First, the accuracy of neoplasms burden estimates in the GBD database largely depends on the original data reported by global neoplasms registries and vital registration systems. It means that in some developing countries lacking health care resources and reliable registration systems, the underdiagnosis and underreporting of neoplasms may lead to an underestimation of the neoplasm burden. Additionally, the COVID-19 pandemic has caused significant disruptions to neoplasms services, leading to severe delays in diagnosis and treatment. Our estimates do not account for the impact of the pandemic, as they are primarily based on data before 2020. During the April 2020 pandemic peak, breast and colorectal cancer screenings dropped by 85% and 75%, respectively, with a significant reduction in outpatient visits[46,47]. In 2020, cancer incidence rates decreased due to missed screenings and treatment delays. Although there was a partial rebound in incidence rates in 2021, the pandemic’s long-term effects on cancer survival and mortality remain uncertain[46]. These factors highlight the need to address the diagnostic service backlog and mitigate the impact of COVID-19 on cancer patients. Moreover, our study found that drug use is a rapidly rising risk factor. However, considering the low monitoring environments, the reliability of estimates for risk factors such as drug use may be compromised due to incomplete and inaccurate data collection. This may lead to misclassification or data quality issues, which could underestimate or overestimate the actual impact of these risk factors. While in low-surveillance regions, the GBD database ensures data reliability through rigorous collection and validation processes. It integrates multi-source data, such as national cancer registries and population health surveys, and subjects them to standardized processing and quality control[48,49]. Although data estimation is often challenging in these regions, the GBD database’s methodology is robust, providing relatively reliable estimates.

Conclusion
Collectively, this study reveals the following key findings: First, with the intensification of global aging, the burden of neoplasms among the elderly remains substantial and varies across different regions and genders. Second, the global burden of neoplasms demonstrates significant geographic heterogeneity, with skin neoplasms currently exhibiting a sharp upward trajectory in incidence. Furthermore, gastrointestinal and respiratory neoplasms are particularly pronouncedly affected by population aging, demonstrating a strong positive correlation between disease burden and advancing age. Regarding risk factors, smoking remains the primary risk factor and contributes most significantly to the burden in high-middle SDI regions. Simultaneously, drug use emerged as the fastest-growing risk factor during 1990–2021, notably within high-SDI regions (exhibiting a 246.44% increase in deaths and 214.28% rise in DALYs), underscoring the urgency of controlling emerging risks.