Disease burden of inflammatory bowel disease and subtypes in older adults in 172 high- and middle-income countries: Trends from 2000 to 2023 and projections to 2040

Abstract

Background:

Inflammatory bowel disease (IBD) in older adults has become a new concern in high- and middle-income countries (HMICs). However, the latest disease burden and temporal trends remain to be systemically clarified.

Methods:

Disease burden data of 172 HMICs were extracted from GBD 2023, including incidence, prevalence, and DALYs on IBD, ulcerative colitis (UC), and Crohn’s disease (CD) among older adults. Stratified analysis was performed based on disease subtype, sex, and gross national income (GNI). A correlation analysis was utilized to evaluate the association of the indicators and income levels. Temporal trends (2000-2023) and future burden up to 2040 were further analyzed.

Results:

In 2023, the incidence, prevalence and DALY rate of IBD in older adults were highest in high-income countries (HCs), and all indicators showed a positive correlation with GNI per capita. From 2000 to 2023, the most significant increase in incidence was observed in Libya, China, and Lebanon. The burden of UC was greater than that of CD, and the incidence ratio of UC/CD was negatively correlated with GNI per capita. The incidence of UC was higher among older males, whereas CD had a higher incidence among older females. Until 2040, the prevalence of IBD and its subtypes would increase across all GNI levels. Notably, the prevalence of UC in lower-middle-income countries (LMCs) may double.

Conclusions:

The disease burden of IBD among older adults in HMICs continues to increase. Future strategies should be customized based on each country’s specific needs and development stage.

INTRODUCTION

Inflammatory bowel disease (IBD) is a challenging chronic inflammatory condition affecting the digestive system, with an increasing disease burden globally.[1] IBD does not only affect younger individuals; several studies on the epidemiology of IBD suggest that a second peak in the incidence of IBD is observed among middle-aged and older adults,[2,3,4] in addition to the younger cohort. Moreover, IBD has a relatively minor impact on life expectancy,[5] and most patients who develop IBD at a young age survive into old age. The incidence of IBD in older individuals has been reported to be on the rise.[6,7] Concurrently, with population aging, a substantial cohort of younger patients is transitioning into old age, further increasing the prevalence of IBD.[8,9] In comparison to younger patients, older patients with IBD are usually associated with more comorbidities, relative frailty, and atypical manifestations,[10] as well as differences in drug efficacy and co-medication profiles.[11] Therefore, IBD among older adults has emerged as a new, distinct research topic, attracting great attention from clinicians and academic specialists.

Existing studies have employed inconsistent definitions of IBD among older adults, particularly, the thresholds of age are different, with lower limits ranging from 55 to 75 years.[6,7,11] The 2016 European Crohn’s and Colitis Organization guideline has classified IBD in individuals aged ≥60. This specific group, covers old patients with new-onset IBD and those who develop IBD at a younger age.[8] IBD encompasses two main subtypes, i.e., ulcerative colitis (UC) and Crohn’s disease (CD). The two subtypes differ in clinical manifestations, complications, and epidemiological characteristics. Two recent publications have reported on the global epidemiological status and trends of IBD among the older population.[9,12] Nonetheless, they do not subdivide disease subtypes further, and their findings are based on data before 2021. With the end of the COVID-19 pandemic, it is necessary to update epidemiological data to better assess the latest burden of IBD for the older population. Furthermore, although population ageing poses a global threat, the degree of ageing correlates with a nation’s economic level.[13] Compared to low-income countries, high- and middle-income countries (HMICs) face more severe health challenges associated with ageing.[13,14] The burden of IBD among older adults is more prominent and important in HMICs.[14] To date, a comprehensive analysis of IBD among older adults in HMICs that includes disease subtypes is lacking. Thus, we conducted this research to systematically evaluate the disease burden of IBD, UC, and CD among older adults in HMICs from 2000 to 2023, and further project future trends, aiming to provide insights for health policymakers and clinicians.

MATERIALS AND METHODS

Study population and data collection

The data analyzed were derived from the Global Burden of Disease Study 2023 (GBD 2023) database, which provides current epidemiological estimates for the disease burden of 375 distinct diseases and injuries in 204 countries and territories.[15] The Global Health Data Exchange (https://ghdx.healthdata.org/gbd-2023) website offers free access. We collected yearly data on IBD, UC and CD among the age group of 60+ years in HMICs from 2000 to 2023. Gross national income (GNI), a metric measuring the economic performance and size of a country or region, is calculated by the total income earned by a nation’s residents and businesses over a specific period. Considering the quantitive results of GNI, the World Bank Group categorizes countries and territories into four groups: high-income countries (HCs), upper-middle-income countries (UMCs), lower-middle-income countries (LMCs), and low-income countries (LCs).[16] In this study, we identified 172 HMICs based on the World Bank Group country classifications, done in 2023.

This study period covered the COVID-19 pandemic, as disruptions in healthcare services may have affected the detection of IBD cases. GBD 2023 has addressed these challenges through several approaches, including expanding data sources, employing statistical models with uncertainty intervals, and, for the first time, fully incorporating data from 2000 to 2023 into the model.[15]

Ethics

This study used de-identified and aggregated data from the publicly available database and there was no direct access to the participants. Ethical approval and informed consent from participants were not required.

Statistical analysis

Primary outcome indicators included numbers and rates of incidence, prevalence, and disability-adjusted life years (DALYs) on IBD, UC, and CD in older adults. The metric of DALYs is commonly adopted to reflect the total years of healthy life lost due to illness, from the time of onset until death. It encompasses years of life lost (YLLs) and years lived with disability (YLDs).[17] Cases were presented in thousands and rates were standardized to a population of 100,000, together with corresponding 95% uncertainty intervals (UIs).

To quantify changes over time, we used percentage change and estimated annual percentage change (EAPC). Percentage change = (cases in 2023 - cases in 2000)/cases in 2000. EAPC is a widely used indicator and represents the average change in the rate per year. It is calculated by fitting a regression line to the logarithm of the rate using time as a regressor variable.[18] The results are interpreted based on a 95% confidence interval (CI). A 95% CI above 0 can be interpreted as an up-regulated tendency, while a 95% CI below 0 can be interpreted as a down-regulated tendency. A 95% CI including 0 means no statistically significant difference.

Sex patterns of the rates were reported and stratified by disease subtype. The association between the disease burden metrics and GNI levels was evaluated using Spearman’s correlation analysis. The UC/CD ratio was calculated by dividing the rate of UC by the rate of CD. We also analyzed the correlation between the UC/CD rate ratio of each indicator and GNI levels.

The Autoregressive Integrated Moving Average (ARIMA) model, a widely adopted statistical approach for time series forecasting and analysis,[19] was employed to forecast future disease burden until 2040. It works by combining three elements: autoregression (using past values to predict future values), integration (differencing the data to remove trends), and moving averages (using past forecast errors to improve predictions). By integrating these three components, the ARIMA model demonstrates strong performance in a variety of time series prediction fields. Given ARIMA extrapolations over 17 years, long-term projections inevitably carried substantial uncertainty. To quantify this uncertainty, we calculated 95% UIs for all projections.

To carry out all data analyses, we adopted the open-source software R (version 4.4.2). A statistically marked difference is typically inferred when the P value is less than 0.05.

RESULTS

Overall results in 2023

In 2023, the incident cases, prevalent cases, and DALYs of IBD among older adults in HMICs were 102.43, 1306.92, and 719.11 thousand, respectively. The overall incidence, prevalence, and DALY rates were 11, 140.39, and 77.25 per 100,000 people, respectively. The disease burden of IBD among older adults varied significantly across regions with different GNI levels. The incidence, prevalence, and DALY rate were the highest in HCs, at 29.58, 446.89, and 221.64 per 100,000 people, respectively. Details are presented in Table 1.

Table 1.

The disease burden of IBD, UC, and CD among older adults in 172 high- and middle-income countries*, with change trends between 2000 and 2023

Disease	Location	Incidence
		Cases 2023, 000s (95% UI)	Percentage change 2000-2023 (100%)	Rates 2023, per 100000 (95% UI)	EAPC 2000-2023 (95% CI)
IBD	All location	102.43 (83.98~126.47)	1.03	11 (9.02~13.59)	0.3 (0.25~0.35)
	GNI-H	60.43 (50.26~72.89)	0.82	29.58 (24.6~35.68)	1.11 (1.02~1.2)
	GNI-UM	14.86 (11.87~19)	1.48	3.18 (2.54~4.06)	0.75 (0.64~0.87)
	GNI-LM	27.14 (21.84~34.58)	1.4	10.5 (8.45~13.37)	0.6 (0.53~0.66)
UC	All location	69.47 (53.84~90.2)	1.05	7.46 (5.78~9.69)	0.32 (0.28~0.36)
	GNI-H	37.72 (29.82~47.08)	0.83	18.46 (14.6~23.05)	1.09 (1~1.18)
	GNI-UM	11.12 (8.42~15.19)	1.5	2.37 (1.8~3.25)	0.77 (0.6~0.93)
	GNI-LM	20.64 (15.6~27.92)	1.38	7.98 (6.04~10.8)	0.52 (0.43~0.61)
CD	All location	32.96 (23.49~43.99)	0.98	3.54 (2.52~4.73)	0.25 (0.18~0.32)
	GNI-H	22.7 (16.22~30.3)	0.82	11.11 (7.94~14.83)	1.14 (1.03~1.25)
	GNI-UM	3.75 (2.65~5.07)	1.45	0.8 (0.57~1.08)	0.72 (0.61~0.83)
	GNI-LM	6.51 (4.61~8.62)	1.47	2.52 (1.78~3.33)	0.84 (0.78~0.89)
Disease	Prevalence
	Cases 2023, 000s (95% UI)		Percentage change 2000-2023 (100%)	Rates 2023, per 100000 (95% UI)	EAPC 2000-2023 (95% CI)
IBD	1306.92 (1074.97~1583.59)		0.9	140.39 (115.48~170.11)	-0.09 (-0.22~0.04)
	912.98 (759.81~1084.35)		0.72	446.89 (371.91~530.77)	0.79 (0.68~0.9)
	135.39 (108.95~173.02)		1.39	28.92 (23.28~36.96)	0.41 (0.21~0.61)
	258.55 (206.21~326.22)		1.58	100.01 (79.76~126.19)	0.6 (0.48~0.73)
UC	888.19 (683.37~1133.67)		0.91	95.41 (73.41~121.78)	-0.11 (-0.23~0.02)
	595.54 (465.5~742.15)		0.71	291.51 (227.85~363.27)	0.74 (0.63~0.85)
	99.58 (74.7~134.79)		1.39	21.27 (15.96~28.8)	0.39 (0.14~0.65)
	193.07 (143.17~256.73)		1.56	74.68 (55.38~99.3)	0.55 (0.41~0.69)
CD	418.73 (316.84~527.46)		0.9	44.98 (34.04~56.66)	-0.06 (-0.2~0.07)
	317.44 (242.31~398.15)		0.75	155.38 (118.61~194.89)	0.89 (0.76~1.01)
	35.81 (26.53~45.79)		1.39	7.65 (5.67~9.78)	0.46 (0.4~0.53)
	65.48 (47.99~83.52)		1.67	25.33 (18.56~32.31)	0.77 (0.65~0.9)
Disease	DALYs
	Cases 2023, 000s (95% UI)		Percentage change 2000-2023 (100%)	Rates 2023, per 100000 (95% UI)	EAPC 2000-2023 (95% CI)
IBD	719.11 (575.8~890.03)		0.8	77.25 (61.85~95.61)	-0.53 (-0.66 ~ -0.39)
	452. 8 (383.94~530.52)		0.94	221.64 (187.93~259.68)	1.04 (0.85~1.22)
	144.1 (109.93~187.55)		0.51	30.78 (23.49~40.07)	-1.77 (-2.03 ~ -1.51)
	122.21 (81.92~171.95)		0.72	47.27 (31.69~66.51)	-1.03 (-1.15 ~ -0.91)
UC	576.94 (455.85~718.73)		0.81	61.98 (48.97~77.21)	-0.54 (-0.71 ~ -0.36)
	353.45 (299.16~411.49)		1.05	173.01 (146.43~201.42)	1.2 (0.92~1.47)
	124.6 (92.61~165.16)		0.46	26.62 (19.78~35.28)	-1.96 (-2.24 ~ -1.67)
	98.89 (64.09~142.08)		0.65	38.25 (24.79~54.96)	-1.2 (-1.33 ~ -1.07)
CD	142.17 (104.74~191.85)		0.72	15.27 (11.25~20.61)	-0.49 (-0.59 ~ -0.38)
	99.35 (76.7~128.26)		0.63	48.63 (37.54~62.78)	0.51 (0.31~0.7)
	19.5 (14.06~26.58)		0.95	4.17 (3~5.68)	-0.38 (-0.5 ~ -0.26)
	23.32 (13.98~37)		1.05	9.02 (5.41~14.31)	-0.19 (-0.3 ~ -0.08)

*Stratified by GNI levels. H: High-income; UM: Upper-middle-income; LM: Lower-middle-income

Further analysis of the disease subtypes revealed that the incident cases, prevalent cases, and DALYs of UC in 2023 among HMICs were higher than those of CD, accounting for 67.82%, 67.96%, and 80.23% of the cases of IBD in older adults, respectively. The overall incidence, prevalence, and DALY rates of UC among older adults in HMICs were 7.46, 95.41, and 61.98 per 100,000 people; while those metrics of CD were 3.54, 44.98, and 15.27 per 100,000 people, respectively. When stratified by GNI level, the highest disease burden for both UC and CD was noted in HCs.

National results in 2023

Among 172 HMICs [Figure 1], the highest incidence, prevalence, and DALY rates of IBD among older adults were observed in high-income countries from North America, Europe or Oceania. For example, the highest incidence was noted in New Zealand (43.91, 95% UI: 36.67-50.92) and Canada (38.07, 95% UI: 31.36-45.11). The highest prevalence was found in Canada (661, 95% UI: 540.03-779.37) and Norway (613.24, 95% UI: 536.44-703.37). The highest DALY rate was noted in Netherlands (285.88, 95% UI: 247.35-328.08) and Germany (267.93, 95% UI: 232.48-304.13). On the other hand, the lowest disease burden of IBD among older adults was found predominantly in low-latitude countries. For example, the lowest incidence rate was noted in Mexico (0.39, 95% UI: 0.29-0.51), Thailand (0.77, 95% UI: 0.59-1) and Philippines (0.77, 95% UI: 0.59-1.02). The lowest prevalence rate was also observed in Mexico (3.35, 95% UI: 2.7-4.33), followed by Timor-Leste (7.31, 95% UI: 5.79-9.31) and Cambodia (7.4, 95% UI: 5.79-9.68). Meanwhile, the lowest DALY rate was observed in Sri Lanka (7.01, 95% UI: 5.06-9.33), Singapore (8.11, 95% UI: 6.82-9.66) and Papua New Guinea (10.15, 95% UI: 4.93-20.04).

Figure 1.

Disease burden of IBD among older adults in 2023 and temporal trends from 2000 to 2023 across 172 high- and middle-income countries. (a) Incidence rates in 2023. (b) EAPCs for incidence rates. (c) Prevalence rates in 2023. (d) EAPCs for prevalence rates. (e) DALY rates in 2023. (f) EAPCs for DALY rates

Stratified analysis on disease subtypes in older adults [Figure S1 ^{(680KB, tif)} and S2 ^{(676.9KB, tif)} ] revealed that the highest incidence rates of UC and CD were both observed in New Zealand, at 20.22 (95% UI: 16.57-23.32) and 23.68 (95% UI: 17.32-29.89), respectively. The highest prevalence rate of UC was found in Norway (431.98, 95% UI: 356.21-506.14) and the highest DALY rate was noted in Netherlands (238.89, 95% UI: 204.25-270.04). The highest prevalence rate (319.35, 95% UI: 239.43-395.3) and DALY rate (71.88, 95% UI: 52.7-94.51) of CD were both found in Canada. On the other hand, the lowest burden was generally found in low-latitude countries. For instance, both the lowest incidence and prevalence rates for UC were observed in Mexico (incidence: 0.27 [0.18-0.38]; prevalence: 2.07 [1.51-2.89]). The lowest DALY rate of UC was observed in Sri Lanka (5.58, 95% UI: 3.96-7.42). The lowest incidence rate for CD was in Nicaragua (0.09, 95% UI: 0.06-0.13). The lowest prevalence of CD was observed in Mexico (1.28, 95% UI: 0.93-1.64), and the lowest DALY rate was noted in Micronesia (0.97, 95% UI: 0.59-1.5).

The correlation of disease burden and GNI per capita

As shown in Figure 2, the incidence, prevalence, and DALY rate for IBD, UC, and CD among older adults all had a positive correlation with GNI per capita. However, the incidence ratio between UC and CD among older adults showed a negative correlation (R = -0.233, P = 0.003) with GNI per capita, suggesting that the ratio declined with economic growth.

Figure 2.

Correlation between each indicator and GNI per capita (data from older adults across 172 high- and middle-income countries). a. Correlation of the incidence (A1), prevalence (A2), and DALY rates (A3) of IBD with GNI per capita. b. Correlation of the incidence (B1), prevalence (B2), and DALY rates (B3) of UC with GNI per capita. c. Correlation of the incidence (C1), prevalence (C2), and DALY rates (C3) of CD with GNI per capita. d. Correlation of the incidence ratio (D1), prevalence ratio (D2), and DALY rate ratio (D3) of UC/CD with GNI per capita

Temporal trends

From 2000 to 2023, the incidence and prevalence rates of IBD among older adults showed an upward trend across all GNI levels (HCs, UMCs, and LMCs). Among those, HCs demonstrated the most significant growth, with an EAPC of 1.11 (95% CI: 1.02-1.2) for incidence and 0.79 (95% CI: 0.68-0.9) for prevalence. The DALY rate showed an obvious declining trend in UMCs (EAPC: -1.77; 95% CI: -2.03 to -1.51) and LMCs (EAPC: -1.03; 95% CI: -1.15 to -0.91); while in HCs, it continued to substantially increase (EAPC: 1.04; 95% CI: 0.85-1.22). Regarding disease subtypes, similar patterns were observed in the trends for UC and CD in older adults among different GNI levels. Details are shown in Table 1.

At the national level [Figure 1], from 2000 to 2023, the most significant growth in the incidence rates for IBD among older adults was observed in Libya (EAPC: 2.29; 95% CI: 1.97-2.6), China (EAPC: 2; 95% CI: 1.59-2.41), and Lebanon (EAPC: 1.93,95% CI: 1.51-2.36). The most notable increase in the prevalence rates occurred in France (EAPC: 3.08; 95% CI: 2.6-3.56) and Bahrain (EAPC: 2.46; 95% CI: 2.12-2.8). The DALYs rate declined in approximately half of the countries. A substantial decrease in EAPC was recorded in Northern Mariana Islands (EAPC: -7.6, 95% CI: -8.5 to -6.69), which was considered a statistical artefact due to the small population size.

Regarding disease subgroups in older adults [Figure S1 ^{(680KB, tif)} and S2 ^{(676.9KB, tif)} ], the fastest-growing incidence of UC was observed in Austria (EAPC: 2.47; 95% CI: 1.91-3.04), followed by China (EAPC: 2.25; 95% CI: 1.67-2.82) and Libya (EAPC: 2.2; 95% CI: 1.89-2.52). The most significant increase in the incidence of CD was noted in Libya (EAPC: 2.6; 95% CI: 2.26-2.95), Lebanon (EAPC: 1.91; 95% CI: 1.54-2.28), and Colombia (EAPC: 1.82; 95% CI: 1.54-2.11). The most notable rise in prevalence of both UC (EAPC: 3.15; 95% CI: 2.66-3.65) and CD (EAPC: 2.96; 95% CI: 2.5-3.42) was found in France.

Sex analysis

As illustrated in Figure 3, the incidence rate of IBD was higher among older males than older females. However, the prevalence and DALY rates in IBD were higher in older females, and the gap between males and females gradually converged over time. Further analysis by disease subtype revealed that the incidence and prevalence rates of UC were generally elevated in older males in comparison to older females. Conversely, both incidence and prevalence rates of CD were higher in older females in comparison to older males.

Figure 3.

Sex difference in each disease burden indicator of IBD and subtypes among older adults (data from 172 high- and middle-income countries). a. Sex difference in the incidence (A1), prevalence (A2), and DALY rate (A3) of IBD. b. Sex difference in the incidence (B1), prevalence (B2), and DALY rate (B3) of UC. c. Sex difference in the incidence (C1), prevalence (C2), and DALY rate (C3) of CD

ARIMA prediction

Figure 4 and Table 2 present a stratified analysis of the future disease burden of IBD among older adults by regional economic levels. By 2040, the incidence (30.43, 95% UI: 24.32-36.54), prevalence (499.14, 95% UI: 457.9-540.38) and DALY rates (259.79, 95% UI: 226.29-293.29) in HCs will rise by 2.87%, 11.69%, and 17.21% from 2023, respectively. In UMCs, the incidence (3.23, 95% UI: 2.68-3.79) and prevalence rates (31.53, 95% UI: 18.49-44.58) may increase by 1.57% and 9.02% from 2023, respectively; the DALY rate (19.64, 95% UI: 10.93 ~ 28.34) may drop markedly, by 36.19%. In LMCs, the incidence (11.27, 95% UI: 10.67-11.88) and prevalence rates (117.99, 95% UI: 74.69-161.3) are expected to increase by 7.33% and 17.98% from 2023; while the DALY rate will be stable.

Figure 4.

Predicted trends in the disease burden of IBD among older adults through 2040, stratified by GNI levels. H: High-income; UM: Upper-middle-income; LM: Lower-middle-income. a. Future incidence rate in high-income (A1), upper-middle-income (A2), and lower-middle-income (A3) countries. b. Future prevalence rate in high-income (B1), upper-middle-income (B2), and lower-middle-income (B3) countries. c. Future DALY rate in high-income (C1), upper-middle-income (C2), and lower-middle-income (C3) countries

Table 2.

The projected incidence, prevalence and DALY rates of IBD among older adults in 172 high- and middle-income countries* (forecast to 2040)

The incidence, prevalence and DALYs rates of IBD among older adults: forecast to 2040
Year	Incidence Rates, per 100000 (95% UI)			Prevalence Rates, per 100000 (95% UI)
	GNI-H	GNI-UM	GNI-LM	GNI-H	GNI-UM	GNI-LM
2023	29.58 (24.6~35.68)	3.18 (2.54~4.06)	10.5 (8.45~13.37)	446.89 (371.91~530.77)	28.92 (23.28~36.96)	100.01 (79.76~126.19)
2024	29.72 (29.54~29.9)	3.19 (3.16~3.22)	10.45 (10.37~10.53)	450.71 (447.69~453.72)	29.07 (28.89~29.26)	104.96 (104.07~105.85)
2025	29.84 (29.39~30.29)	3.2 (3.14~3.26)	10.5 (10.33~10.67)	454.89 (446.95~462.83)	29.23 (28.69~29.77)	109.6 (107.08~112.12)
2026	29.94 (29.15~30.73)	3.2 (3.11~3.3)	10.55 (10.32~10.77)	458.95 (445.14~472.77)	29.38 (28.4~30.37)	113.65 (108.82~118.49)
2027	30.02 (28.86~31.19)	3.21 (3.08~3.34)	10.6 (10.33~10.87)	462.55 (443.08~482.02)	29.54 (28.02~31.05)	116.96 (109.27~124.66)
2028	30.09 (28.52~31.66)	3.21 (3.04~3.38)	10.65 (10.34~10.96)	465.56 (441.48~489.65)	29.69 (27.58~31.8)	119.47 (108.54~130.4)
2029	30.15 (28.17~32.14)	3.21 (3.01~3.42)	10.7 (10.36~11.05)	468.11 (440.73~495.49)	29.84 (27.08~32.6)	121.19 (106.82~135.56)
2030	30.21 (27.81~32.6)	3.22 (2.98~3.46)	10.76 (10.38~11.13)	470.4 (440.9~499.91)	30 (26.52~33.47)	122.21 (104.33~140.09)
2031	30.25 (27.44~33.06)	3.22 (2.94~3.5)	10.81 (10.41~11.21)	472.7 (441.87~503.54)	30.15 (25.91~34.39)	122.63 (101.3~143.96)
2032	30.29 (27.07~33.5)	3.22 (2.91~3.53)	10.86 (10.43~11.29)	475.2 (443.45~506.95)	30.3 (25.25~35.36)	122.59 (97.95~147.23)
2033	30.32 (26.7~33.93)	3.22 (2.88~3.57)	10.91 (10.46~11.37)	477.97 (445.44~510.51)	30.46 (24.55~36.37)	122.21 (94.45~149.96)
2034	30.34 (26.34~34.35)	3.23 (2.85~3.6)	10.96 (10.49~11.44)	481 (447.61~514.38)	30.61 (23.8~37.42)	121.61 (90.97~152.25)
2035	30.36 (25.98~34.75)	3.23 (2.82~3.64)	11.02 (10.51~11.52)	484.17 (449.74~518.6)	30.77 (23.01~38.52)	120.91 (87.63~154.19)
2036	30.38 (25.63~35.13)	3.23 (2.79~3.67)	11.07 (10.54~11.59)	487.37 (451.67~523.07)	30.92 (22.18~39.66)	120.17 (84.49~155.86)
2037	30.4 (25.29~35.5)	3.23 (2.76~3.7)	11.12 (10.58~11.66)	490.5 (453.36~527.63)	31.07 (21.31~40.84)	119.48 (81.62~157.35)
2038	30.41 (24.96~35.86)	3.23 (2.73~3.73)	11.17 (10.61~11.73)	493.49 (454.89~532.1)	31.23 (20.4~42.05)	118.87 (79.03~158.72)
2039	30.42 (24.64~36.2)	3.23 (2.7~3.76)	11.22 (10.64~11.81)	496.36 (456.36~536.36)	31.38 (19.46~43.3)	118.37 (76.73~160.02)
2040	30.43 (24.32~36.54)	3.23 (2.68~3.79)	11.27 (10.67~11.88)	499.14 (457.9~540.38)	31.53 (18.49~44.58)	117.99 (74.69~161.3)
The incidence, prevalence and DALYs rates of IBD among older adults: forecast to 2040
Year	DALYs Rates, per 100000 (95% UI)
	GNI-H		GNI-UM		GNI-LM
2023	221.64 (187.93~259.68)		30.78 (23.49~40.07)		47.27 (31.69~66.51)
2024	223.88 (215.76~232.01)		29.19 (27.81~30.57)		46.41 (44.47~48.34)
2025	226.13 (214.64~237.62)		28.59 (26.04~31.15)		46.41 (42.68~50.14)
2026	228.37 (214.3~242.44)		27.99 (24.66~31.33)		46.41 (41.5~51.31)
2027	230.62 (214.37~246.87)		27.4 (23.43~31.37)		46.41 (40.56~52.26)
2028	232.86 (214.69~251.03)		26.8 (22.28~31.32)		46.41 (39.75~53.07)
2029	235.1 (215.2~255)		26.2 (21.2~31.2)		46.41 (39.03~53.79)
2030	237.35 (215.85~258.84)		25.61 (20.16~31.05)		46.41 (38.37~54.45)
2031	239.59 (216.61~262.57)		25.01 (19.16~30.86)		46.41 (37.76~55.06)
2032	241.84 (217.46~266.21)		24.41 (18.18~30.65)		46.41 (37.19~55.62)
2033	244.08 (218.39~269.77)		23.82 (17.22~30.41)		46.41 (36.66~56.16)
2034	246.32 (219.38~273.27)		23.22 (16.28~30.15)		46.41 (36.15~56.67)
2035	248.57 (220.42~276.71)		22.62 (15.36~29.88)		46.41 (35.67~57.15)
2036	250.81 (221.52~280.1)		22.02 (14.45~29.6)		46.41 (35.21~57.61)
2037	253.05 (222.66~283.45)		21.43 (13.56~29.3)		46.41 (34.76~58.05)
2038	255.3 (223.83~286.77)		20.83 (12.67~28.99)		46.41 (34.33~58.48)
2039	257.54 (225.04~290.04)		20.23 (11.8~28.67)		46.41 (33.92~58.9)
2040	259.79 (226.29~293.29)		19.64 (10.93~28.34)		46.41 (33.52~59.3)

*Stratified by GNI levels. H: High-income; UM: Upper-middle-income; LM: Lower-middle-income

As shown in Figure S3 ^{(266.8KB, tif)} -S4 ^{(267.3KB, tif)} and Table S1-S2, remarkable increases in disease burden (greater than 10%) of the two disease subtypes among older adults will occur mainly in HCs and LMCs. For instance, by 2040, the incidence (21.18, 95% UI: 16.34-26.02), prevalence (325.22, 95% UI: 298.13-352.31), and DALY rates (208.07, 95% UI: 176.13-240.01) of UC in HCs are projected to increase by 14.73%, 11.56%, and 20.26% compared to 2023, respectively. The prevalence (175.88, 95% UI: 169.03-182.73) and DALY rates (58.09, 95% UI: 36.21-79.96) of CD may increase by 13.19% and 19.45%, respectively. In LMCs, the prevalence rate (150.42, 95% UI: 86.28-214.56) of UC may rise sharply from its current low level, by 101.42% compared to 2023; the incidence (2.8, 95% UI: 2.69-2.91) and prevalence rates (30.82, 95% UI: 19.69-41.95) of CD are expected to rise by 11.11% and 21.67%, respectively. As for UMCs, a significant downward trend may be observed in the DALY rate (15.8, 95% UI: 7.48-24.13) on UC, with a 40.65% decrease from 2023.

Table S1.

The projected incidence, prevalence and DALY rates of UC among older adults in 172 high- and middle-income countries* (forecast to 2040)

Year	Incidence Rates, per 100000 (95% UI)			Prevalence Rates, per 100000 (95% UI)
	GNI-H	GNI-UM	GNI-LM	GNI-H	GNI-UM	GNI-LM
2023	18.46 (14.6~23.05)	2.37 (1.8~3.25)	7.98 (6.04~10.8)	291.51 (227.85~363.27)	21.27 (15.96~28.8)	74.68 (55.38~99.3)
2024	18.62 (18.51~18.73)	2.37 (2.35~2.39)	7.92 (7.85~7.99)	294.57 (292.61~296.54)	21.31 (21.16~21.46)	78.58 (77.96~79.19)
2025	18.78 (18.52~19.04)	2.37 (2.32~2.42)	7.86 (7.69~8.03)	297.77 (292.61~302.93)	21.34 (20.88~21.8)	82.71 (80.96~84.45)
2026	18.94 (18.51~19.37)	2.37 (2.28~2.46)	7.8 (7.52~8.08)	300.63 (291.68~309.58)	21.37 (20.47~22.27)	86.99 (83.58~90.39)
2027	19.1 (18.47~19.73)	2.37 (2.24~2.5)	7.74 (7.34~8.14)	302.92 (290.33~315.51)	21.4 (19.98~22.81)	91.37 (85.81~96.92)
2028	19.26 (18.41~20.11)	2.37 (2.19~2.55)	7.68 (7.13~8.23)	304.63 (289.05~320.22)	21.43 (19.46~23.39)	95.81 (87.66~103.96)
2029	19.42 (18.33~20.51)	2.37 (2.14~2.6)	7.62 (6.92~8.32)	305.95 (288.2~323.71)	21.46 (18.92~23.99)	100.3 (89.15~111.45)
2030	19.58 (18.22~20.94)	2.37 (2.09~2.65)	7.56 (6.69~8.43)	307.14 (287.95~326.33)	21.49 (18.36~24.62)	104.82 (90.28~119.35)
2031	19.74 (18.1~21.38)	2.37 (2.03~2.71)	7.5 (6.45~8.55)	308.43 (288.3~328.55)	21.52 (17.76~25.28)	109.35 (91.09~127.62)
2032	19.9 (17.96~21.84)	2.37 (1.97~2.77)	7.44 (6.19~8.69)	309.95 (289.16~330.75)	21.55 (17.12~25.98)	113.9 (91.59~136.21)
2033	20.06 (17.81~22.31)	2.37 (1.91~2.83)	7.38 (5.93~8.83)	311.75 (290.38~333.12)	21.58 (16.44~26.72)	118.45 (91.79~145.11)
2034	20.22 (17.64~22.8)	2.37 (1.84~2.9)	7.32 (5.66~8.98)	313.75 (291.78~335.72)	21.61 (15.73~27.49)	123.01 (91.73~154.3)
2035	20.38 (17.46~23.3)	2.37 (1.77~2.97)	7.26 (5.38~9.14)	315.85 (293.17~338.53)	21.64 (14.98~28.3)	127.58 (91.4~163.76)
2036	20.54 (17.26~23.82)	2.37 (1.69~3.05)	7.2 (5.09~9.31)	317.92 (294.41~341.43)	21.67 (14.2~29.14)	132.15 (90.83~173.46)
2037	20.7 (17.05~24.35)	2.37 (1.62~3.12)	7.14 (4.79~9.49)	319.91 (295.48~344.33)	21.7 (13.39~30.01)	136.71 (90.02~183.4)
2038	20.86 (16.82~24.9)	2.37 (1.54~3.2)	7.08 (4.48~9.68)	321.77 (296.4~347.13)	21.73 (12.55~30.91)	141.28 (88.99~193.58)
2039	21.02 (16.59~25.45)	2.37 (1.45~3.29)	7.02 (4.17~9.87)	323.52 (297.25~349.79)	21.76 (11.69~31.83)	145.85 (87.74~203.96)
2040	21.18 (16.34~26.02)	2.37 (1.37~3.37)	6.96 (3.84~10.08)	325.22 (298.13~352.31)	21.79 (10.8~32.78)	150.42 (86.28~214.56)
Year	DALYs Rates, per 100000 (95% UI)
	GNI-H		GNI-UM		GNI-LM
2023	173.01 (146.43~201.42)		26.62 (19.78~35.28)		38.25 (24.79~54.96)
2024	175.07 (167.33~182.82)		25.05 (23.76~26.35)		37.15 (35.51~38.79)
2025	177.13 (166.18~188.09)		24.48 (22.04~26.91)		36.68 (33.58~39.79)
2026	179.2 (165.78~192.61)		23.9 (20.71~27.08)		36.21 (32.14~40.29)
2027	181.26 (165.77~196.75)		23.32 (19.53~27.11)		35.75 (30.89~40.6)
2028	183.32 (166~200.64)		22.74 (18.43~27.05)		35.28 (29.75~40.8)
2029	185.38 (166.41~204.36)		22.16 (17.39~26.94)		34.81 (28.68~40.93)
2030	187.45 (166.95~207.94)		21.58 (16.38~26.79)		34.34 (27.67~41.01)
2031	189.51 (167.6~211.42)		21.01 (15.41~26.6)		33.87 (26.7~41.05)
2032	191.57 (168.33~214.81)		20.43 (14.47~26.39)		33.41 (25.76~41.05)
2033	193.63 (169.13~218.13)		19.85 (13.55~26.15)		32.94 (24.85~41.02)
2034	195.69 (170~221.39)		19.27 (12.64~25.9)		32.47 (23.96~40.98)
2035	197.76 (170.92~224.59)		18.69 (11.75~25.64)		32 (23.1~40.91)
2036	199.82 (171.89~227.75)		18.12 (10.88~25.36)		31.53 (22.25~40.82)
2037	201.88 (172.89~230.87)		17.54 (10.01~25.07)		31.07 (21.41~40.72)
2038	203.94 (173.94~233.95)		16.96 (9.16~24.76)		30.6 (20.59~40.61)
2039	206 (175.02~236.99)		16.38 (8.31~24.45)		30.13 (19.78~40.48)
2040	208.07 (176.13~240.01)		15.8 (7.48~24.13)		29.66 (18.98~40.35)

*Stratified by GNI levels. H: High-income; UM: Upper-middle-income; LM: Lower-middle-income

Table S2.

The projected incidence, prevalence and DALY rates of CD among older adults in 172 high- and middle-income countries* (forecast to 2040)

Year	Incidence Rates, per 100000 (95% UI)			Prevalence Rates, per 100000 (95% UI)			DALYs Rates, per 100000 (95% UI)
	GNI-H	GNI-UM	GNI-LM	GNI-H	GNI-UM	GNI-LM	GNI-H	GNI-UM	GNI-LM
2023	11.11 (7.94~14.83)	0.8 (0.57~1.08)	2.52 (1.78~3.33)	155.38 (118.61~194.89)	7.65 (5.67~9.78)	25.33 (18.56~32.31)	48.63 (37.54~62.78)	4.17 (3~5.68)	9.02 (5.41~14.31)
2024	11.07 (10.98~11.16)	0.81 (0.8~0.82)	2.54 (2.51~2.56)	156.08 (155.08~157.08)	7.71 (7.68~7.74)	26.39 (26.12~26.66)	49.19 (48.09~50.28)	4.15 (4.06~4.25)	9.02 (8.74~9.3)
2025	11.02 (10.8~11.24)	0.81 (0.79~0.83)	2.55 (2.52~2.59)	157.02 (154.82~159.22)	7.76 (7.68~7.83)	27.27 (26.48~28.06)	49.74 (47.84~51.64)	4.13 (4~4.27)	9.02 (8.63~9.41)
2026	10.97 (10.59~11.36)	0.82 (0.78~0.85)	2.57 (2.52~2.61)	158.26 (154.87~161.66)	7.8 (7.67~7.92)	27.98 (26.48~29.48)	50.3 (47.53~53.07)	4.12 (3.95~4.28)	9.02 (8.54~9.5)
2027	10.94 (10.37~11.5)	0.82 (0.77~0.86)	2.59 (2.53~2.64)	159.77 (155.42~164.12)	7.83 (7.65~8)	28.56 (26.28~30.84)	50.86 (47.13~54.58)	4.10 (3.91~4.29)	9.02 (8.46~9.58)
2028	10.91 (10.16~11.65)	0.82 (0.76~0.88)	2.6 (2.54~2.66)	161.43 (156.49~166.36)	7.86 (7.64~8.07)	29.02 (25.94~32.1)	51.41 (46.67~56.16)	4.08 (3.86~4.29)	9.02 (8.4~9.64)
2029	10.88 (9.96~11.8)	0.83 (0.75~0.9)	2.62 (2.55~2.68)	163.08 (157.89~168.27)	7.89 (7.64~8.13)	29.4 (25.52~33.27)	51.97 (46.12~57.81)	4.06 (3.83~4.3)	9.02 (8.34~9.7)
2030	10.87 (9.78~11.96)	0.83 (0.74~0.92)	2.64 (2.57~2.7)	164.59 (159.35~169.83)	7.92 (7.65~8.18)	29.7 (25.04~34.35)	52.52 (45.51~59.53)	4.04 (3.79~4.3)	9.02 (8.28~9.76)
2031	10.85 (9.6~12.11)	0.84 (0.73~0.94)	2.65 (2.58~2.73)	165.87 (160.63~171.11)	7.95 (7.66~8.23)	29.94 (24.53~35.36)	53.08 (44.84~61.32)	4.02 (3.75~4.29)	9.02 (8.23~9.81)
2032	10.85 (9.44~12.25)	0.84 (0.71~0.97)	2.67 (2.59~2.75)	166.89 (161.64~172.14)	7.98 (7.68~8.28)	30.14 (23.99~36.29)	53.64 (44.1~63.17)	4.01 (3.72~4.29)	9.02 (8.18~9.86)
2033	10.84 (9.29~12.39)	0.84 (0.7~0.99)	2.69 (2.6~2.77)	167.73 (162.47~172.98)	8.02 (7.7~8.33)	30.3 (23.44~37.16)	54.19 (43.3~65.08)	3.99 (3.68~4.29)	9.02 (8.14~9.9)
2034	10.83 (9.15~12.52)	0.85 (0.68~1.02)	2.7 (2.61~2.79)	168.49 (163.22~173.75)	8.05 (7.72~8.38)	30.43 (22.89~37.97)	54.75 (42.45~67.05)	3.97 (3.65~4.29)	9.02 (8.09~9.95)
2035	10.83 (9.02~12.65)	0.85 (0.66~1.04)	2.72 (2.63~2.81)	169.3 (163.96~174.64)	8.09 (7.75~8.43)	30.53 (22.33~38.73)	55.31 (41.54~69.07)	3.95 (3.62~4.28)	9.02 (8.05~9.99)
2036	10.83 (8.89~12.77)	0.86 (0.65~1.07)	2.73 (2.64~2.83)	170.27 (164.71~175.84)	8.12 (7.77~8.48)	30.62 (21.79~39.45)	55.86 (40.57~71.15)	3.93 (3.59~4.28)	9.02 (8.01~10.03)
2037	10.83 (8.77~12.88)	0.86 (0.63~1.09)	2.75 (2.65~2.85)	171.46 (165.52~177.41)	8.16 (7.79~8.53)	30.69 (21.25~40.12)	56.42 (39.55~73.28)	3.91 (3.56~4.27)	9.02 (7.98~10.06)
2038	10.83 (8.66~12.99)	0.87 (0.61~1.12)	2.77 (2.67~2.87)	172.85 (166.49~179.2)	8.19 (7.81~8.58)	30.74 (20.72~40.76)	56.97 (38.49~75.46)	3.90 (3.53~4.27)	9.02 (7.94~10.1)
2039	10.83 (8.55~13.1)	0.87 (0.59~1.15)	2.78 (2.68~2.89)	174.35 (167.68~181.03)	8.23 (7.83~8.62)	30.78 (20.2~41.37)	57.53 (37.37~77.69)	3.88 (3.49~4.26)	9.02 (7.9~10.14)
2040	10.83 (8.45~13.2)	0.87 (0.57~1.18)	2.8 (2.69~2.91)	175.88 (169.03~182.73)	8.26 (7.85~8.67)	30.82 (19.69~41.95)	58.09 (36.21~79.96)	3.86 (3.46~4.25)	9.02 (7.87~10.17)

*Stratified by GNI levels. H: High-income; UM: Upper-middle-income; LM: Lower-middle-income

DISCUSSION

Population aging, a major social trend of the 21^st century, has widespread effects on both disease and health. In 2020, the United Nations General Assembly established the Decade of Healthy Ageing (2021-2030), aiming to foster comprehensive care and health services tailored to older individuals.[20] The degree of aging and major diseases vary among different economies.[14] Compared to low-income countries, HMICs face more severe aging population problems, particularly non-communicable and chronic diseases.[14] IBD, a non-communicable chronic inflammatory disease, severely affects health and can lead to disability. In-depth understanding of the progression tendency of IBD among the older population in HMICs is crucial for assessing related healthcare needs.

Our study analyzed the disease burden and temporal trends of IBD among older individuals in HMICs from 2000 to 2023, revealing variations across different GNI levels, disease subtypes and sex groups. In 2023, the incidence, prevalence and DALY rates were the highest in HCs and these metrics correlated positively with GNI per capita. These results are consistent with those of Liu et al.[12] IBD first emerged in Western developed countries, nearly a century earlier than other regions,[21] and its incidence rapidly increased in the latter half of the 20^th century.[21] Aging is also an important influencing factor since the vast majority of developed countries have already entered deep or even super-aged societies.[13] Recommendations tailored to older patients have been incorporated into clinical guidelines in some developed countries, including vaccination, cancer screening, and geriatric care.[22,23] Nevertheless, high-quality evidence regarding optimal management strategies for older individuals with IBD remains limited. Additionally, while many studies have investigated environmental risk factors for IBD,[24] those for older adults need to be further elucidated. We also observed that the lowest disease burden occurred in low-latitude regions. Although these countries are predominantly upper-middle-income or lower-middle-income, suggesting that socio-economic development levels may partially account for their lower disease burden, an independent environmental role of latitude cannot be ruled out. For example, previous studies have linked high latitude to IBD morbidity, possibly reflecting environmental factors like reduced exposure to vitamin D and lower temperature.[25,26,27]

The temporal trend analysis identified the greatest increase in the incidence of IBD among older individuals in non-traditional high-incidence areas, such as Libya, China, and Lebanon. As one of the fastest-growing emerging economies, China is reportedly experiencing an explosive surge in IBD,[4,21,28] consistent with the trends in other East Asian countries.[29] The disease burden of IBD within the Middle East and North Africa region is also reported to rise,[30] though relevant literature is scarce. Our study further confirms the upward tendency of UC and CD among older adults in these regions, which may be strongly linked to the rapid economic growth, westernization of lifestyle, environmental pollution, and advances in medical technology.[21,28] However, access to IBD-specific healthcare resources remains uneven across regions and populations. For example, in China, IBD-specific resources are currently concentrated in regional top-tier hospitals, while late-onset IBD receives insufficient attention. To address this uneven distribution, it is imperative to enhance primary care capacity through tiered healthcare and medical alliances, and strengthen disease education and surveillance, to improve the accessibility and convenience of healthcare for older adults. A sharp increase in the prevalence of IBD was observed in Bahrain, second only to France. We further analyzed the burden of IBD among older adults in the Gulf Cooperation Council (GCC) region [Supplementary Table S3], where most countries exhibited rising prevalence of UC and CD. Notably, the increase in UC prevalence in Bahrain (EAPC: 2.91; 95% CI: 2.67-3.15) was significantly higher than in other countries. Beyond factors such as Western culture and improved diagnostic capacity, the specific drivers of this exceptionally pronounced increase need to be further explored.[31] In 2023, the prevalence of IBD among older adults in GCC countries remained relatively low, ranging from 46.05 (95% UI: 37.25-56.02) per 100,000 in Saudi Arabia to 86.38 (95% UI: 69.17-108.73) per 100,000 in Qatar. However, as the higher-risk population ages,[32] the prevalence could increase substantially in the future. Significant variations were observed in the changes in DALY rates, with a significant increase in both UC and CD observed in Saudi Arabia. Another GCC study indicates that IBD DALYs are primarily driven by disability rather than mortality.[32] Hence, healthcare systems should shift to integrated chronic disease management approaches, rather than acute care models.

Table S3.

Disease burden of IBD, UC, and CD among older adults in the Gulf Cooperation Council (GCC) countries, 2000–2023

Disease	Location	Incidence		Prevalence		DALYs
		Rates 2023, per 100000 (95% UI)	EAPC 2000-2023 (95% CI)	Rates 2023, per 100000 (95% UI)	EAPC 2000-2023 (95% CI)	Rates 2023, per 100000 (95% UI)	EAPC 2000-2023 (95% CI)
IBD	Bahrain	2.95 (2.27~3.86)	1.27 (0.8~1.73)	66.24 (54.34~81.76)	2.46 (2.12~2.8)	26.84 (18.9~38.34)	-2.12 (-2.35~-1.88)
	Kuwait	4.6 (3.51~6.22)	1.08 (0.94~1.22)	83.14 (66.74~107.86)	0.67 (0.31~1.02)	24.51 (19.52~32.22)	0.12 (-1.81~2.08)
	Oman	4.88 (3.83~6.6)	1.54 (1.3~1.78)	66.72 (51.55~87.96)	0.02 (-0.23~0.26)	38.88 (25.72~55.59)	0.33 (-0.1~0.77)
	Qatar	5.3 (4.03~7.1)	1.34 (1.22~1.46)	86.38 (69.17~108.73)	0.05 (-0.05~0.15)	33.69 (23.67~45.47)	-2.86 (-3.13~-2.59)
	Saudi Arabia	3.09 (2.4~4.01)	-0.28 (-0.58~0.03)	46.05 (37.25~56.02)	1.01 (0.69~1.32)	19.95 (12.59~28.34)	1.96 (1.56~2.36)
	United Arab Emirates	5.82 (4.51~7.7)	0.41 (0.36~0.46)	75.58 (59.76~97.72)	0.58 (0.45~0.71)	13.82 (8.99~20.36)	0.02 (-0.13~0.17)
UC	Bahrain	1.72 (1.2~2.56)	1.61 (0.89~2.33)	40.67 (30.56~52.82)	2.91 (2.67~3.15)	19.29 (12.66~28.43)	-2.47 (-2.75~-2.19)
	Kuwait	3.74 (2.67~5.33)	1.09 (0.93~1.25)	62.96 (47.13~86.57)	0.73 (0.27~1.19)	18.13 (13.86~23.88)	0.68 (-1.2~2.6)
	Oman	3.68 (2.67~5.25)	1.49 (1.26~1.72)	49.06 (34.88~66.8)	0.03 (-0.21~0.27)	32.19 (20.25~47.83)	0.35 (-0.1~0.8)
	Qatar	4.08 (2.87~5.82)	1.23 (1.12~1.34)	63.93 (47.32~85.2)	0.03 (-0.07~0.13)	26.86 (18.29~35.4)	-3.06 (-3.32~-2.81)
	Saudi Arabia	1.61 (1.15~2.49)	-1.02 (-1.41~-0.63)	26.53 (19.59~35.26)	0.5 (0.23~0.77)	13.74 (8.1~19.16)	1.67 (1.26~2.08)
	United Arab Emirates	4.48 (3.1~6.4)	0.39 (0.33~0.44)	56.48 (41.26~77.33)	0.54 (0.42~0.66)	10.15 (6.22~16.07)	-0.09 (-0.24~0.06)
CD	Bahrain	1.23 (0.85~1.7)	0.83 (0.56~1.1)	25.58 (19.44~31.98)	1.83 (1.07~2.6)	7.55 (4.84~11.34)	-1.1 (-1.36~-0.85)
	Kuwait	0.86 (0.58~1.19)	1.03 (0.92~1.14)	20.18 (15.1~25.44)	0.49 (0.44~0.55)	6.38 (4.49~8.56)	-1.2 (-3.21~0.86)
	Oman	1.19 (0.82~1.66)	1.7 (1.42~1.97)	17.67 (12.71~23.19)	-0.01 (-0.26~0.25)	6.69 (4.1~10.87)	0.24 (-0.1~0.59)
	Qatar	1.21 (0.83~1.63)	1.71 (1.54~1.89)	22.44 (16.97~28.75)	0.11 (0.02~0.21)	6.83 (4.15~10.32)	-1.92 (-2.25~-1.6)
	Saudi Arabia	1.47 (0.99~2)	0.65 (0.45~0.86)	19.53 (14.16~24.92)	1.78 (1.39~2.17)	6.2 (3.69~9.3)	2.67 (2.28~3.05)
	United Arab Emirates	1.33 (0.87~1.86)	0.49 (0.44~0.54)	19.11 (13.61~24.81)	0.7 (0.54~0.86)	3.67 (2.18~5.55)	0.32 (0.12~0.51)

The DALY rates of IBD in the older population declined markedly in UMCs and LMCs, despite rising incidence and prevalence. This divergence may be closely associated with improvements in the management of IBD in these areas, particularly in UMCs. The implementation of specialized IBD care, multidisciplinary team approaches, early diagnosis, and access to biologics and other advanced therapies, has effectively reduced hospitalization rates, mortality, and disability in older patients.[32,33]

In our study, the disease burden of UC among older individuals was markedly higher in comparison to CD. However, the disparity between UC and CD was not constant. We observed a negative correlation between the incidence ratio and GNI per capita, suggesting that the disparity in incidence between UC and CD in the older population diminished as economic conditions improved. Historically, UC was first reported[29,34] and the majority of reports have generally indicated the predominance of UC over CD.[2,3,29,34,35] As time progresses, the ratio of UC to CD in the Western world has been gradually stabilizing. In some regions, the incidence and prevalence rates of CD have surpassed those of UC,[36,37] consistent with our finding of higher CD incidence among older adults in New Zealand.[37] A Latin American study indicates a pronounced rise in the proportion of CD in regions with faster economic advancement and higher levels of industrialization,[35] likely due to increased susceptibility to CD and easier access to higher-quality medical care in more developed regions. Currently, with the widespread use of colonoscopy, the feasibility of diagnosing UC globally has improved. However, the detection of CD in underdeveloped regions remains relatively challenging. Additionally, the ratio of UC to CD is reported to be age-associated and more pronounced in older individuals than in young adults,[36] which may be partly influenced by differences in onset age and etiologic factors between the two subtypes.[24] Despite the clinical differences between UC and CD, guidelines for older adults with IBD still lack subtype-specific recommendations.[22,23] Given the marked variations in the burden of UC and CD across countries, policies addressing healthcare expenditures, care resources, and disease education for older patients should consider the distinct trends of each subtype.

In terms of gender, some studies from Europe and North America have suggested the predominance of females in young patients with CD.[8,38,39] As females enter postmenopause, the incidence of CD decreases and becomes more equal to, or even less than that in males.[3,40] In other studies from Asian countries, male patients predominated in both CD and UC cohorts.[4,29] Different research results may be due to variables including ethnicity, geographic region, age distribution, and disease subtypes. The sex-specific epidemiological characteristics of IBD patients differ between late-onset and young-onset cohorts.[8,10] Liu et al.[12] recently suggested a higher incidence of IBD in older males than in older females, but did not perform stratified analysis by subtype. In our study, older females with CD were more prevalent, while UC was more prevalent in older males. This sex-related disparity may be explained by sex hormones, particularly estrogen levels.[38,39] However, notable differences in estrogen levels between men and women are primarily pre-menopausal. After menopause, estrogen levels converge,[41] yet older women still exhibit a higher incidence rate of CD. Thus, in addition to estrogen levels, other contributing factors need to be further investigated, including sex hormones other than estrogen, the effect of genes on sex chromosomes, the gut microbiota, dietary habits, smoking, as well as obesity.[41,42,43,44]

The COVID-19 pandemic has a complex effect on the epidemiology of IBD. Some studies reported a decrease in the incidence of IBD during the early pandemic,[45,46] likely due to lockdowns, healthcare strain, and diagnostic delays. Atia et al.[45] report more obvious changes in the incidence of IBD in older adults, possibly related to strict social restrictions. Other studies suggest an increased risk of autoimmune diseases, including IBD following COVID-19.[47,48] A recent systematic review has found that the risk of developing IBD after SARS-CoV-2 infection is 39% higher than in uninfected individuals.[48] Alvisi et al.[46] have observed a transient decline in the incidence of pediatric IBD in 2020, followed by a marked rise in 2021, suggesting a potential link between infection and the pathogenesis of IBD. With new data continuously updated, long-term epidemiological changes after the pandemic need to be clarified in further studies.

By 2040, IBD and subtypes will remain a serious challenge among older adults from HMICs. In HCs, the prevalence and DALY rates of IBD among older adults are projected to continue rising. The management of IBD in developed countries is relatively superior, but multimorbidity, frailty, polypharmacy, and care in older adults remain challenging. With the rising prevalence of IBD, the costs from long-term expensive treatments and intensified monitoring will accordingly increase. Proactive measures are necessary, including controlling drug costs, reducing environmental risk exposure, and exploring new payment approaches. For UMCs, the incidence and prevalence rates of CD in older adults may increase to a certain extent. The capacity to recognize, diagnose, and manage CD in older adults needs to be further enhanced. For LMCs, the prevalence of IBD among older adults will surge significantly, and UC prevalence may double, indicating particularly severe healthcare and economic pressures in the future. It is urgent to develop contextualized guidelines and strategies and implement proactive policy measures, such as promoting diagnostic and endoscopic training, enhancing drug accessibility, and establishing disease registration systems. Promoting access to biosimilars in LMCs and prioritizing biotherapeutic targets through public health impact assessments may help to balance economic costs and resource utilization.[49]

This study has several limitations. (1) The data from GBD 2023 are estimates produced by integrating a variety of sources, which may be affected by the model and algorithm. Differences in input data quality and reporting mechanisms across different countries and regions could lead to uncertainty. When data are scarce or missing, the model has a limited ability to accurately estimate trends, potentially resulting in statistical bias. Although GBD estimates were adjusted for pandemic-related disruptions using methodological approaches, residual uncertainty remains. Thus, trends covering the pandemic period should be interpreted cautiously. (2) In addition to UC and CD, there exists indeterminate colitis. GBD 2023 assumed that indeterminate colitis cases would be ultimately confirmed as UC or CD, and the outputs for UC and CD incorporated the adjustment for indeterminate colitis.[15] This may introduce some bias. However, given the low proportion of indeterminate colitis,[50] this bias is considered negligible. (3) In future projections, the economic levels of countries are based on the 2023 income classification. For rapidly growing economies, such as Vietnam and the Philippines, future income levels may be reclassified. Due to rapid changes in environmental factors and marked improvements in diagnostic capacity, the actual disease burden in these countries may be underestimated. Moreover, the ARIMA projections over 17 years may carry substantial uncertainty, particularly following the COVID-19 pandemic.

In conclusion, the disease burden of IBD among older adults in HMICs varied across different economic levels, disease subtypes, and genders. By 2040, the prevalence of IBD and its subtypes would increase across all GNI levels. Notably, the prevalence of UC in LMCs may double. Future strategies aimed at alleviating the burden of IBD among the older population should be customized to the specific needs and development stage of each country.

Conflicts of interest

There are no conflicts of interest.

Figure S1

Disease burden of UC among older adults in 2023 and temporal trends from 2000 to 2023 across 172 high- and middle-income countries. (a) Incidence rates in 2023. (b) EAPCs for incidence rates. (c) Prevalence rates in 2023. (d) EAPCs for prevalence rates. (e) DALY rates in 2023. (f) EAPCs for DALY rates

Figure S2

Disease burden of CD among older adults in 2023 and temporal trends from 2000 to 2023 across 172 high- and middle-income countries. (a) Incidence rates in 2023. (b) EAPCs for incidence rates. (c) Prevalence rates in 2023. (d) EAPCs for prevalence rates. (e) DALY rates in 2023. (f) EAPCs for DALY rates

Figure S3

Predicted trends in the disease burden of UC among older adults through 2040, stratified by GNI levels. H: High-income; UM: Upper-middle-income; LM: Lower-middle-income. A. Future incidence rate in high-income (A1), upper-middle-income (A2), and lower-middle-income (A3) countries. B. Future prevalence rate in high-income (B1), upper-middle-income (B2), and lower-middle-income (B3) countries. C. Future DALY rate in high-income (C1), upper-middle-income (C2), and lower-middle-income (C3) countries

Figure S4

Predicted trends in the disease burden of CD among older adults through 2040, stratified by GNI levels. H: High-income; UM: Upper-middle-income; LM: Lower-middle-income. A. Future incidence rate in high-income (A1), upper-middle-income (A2), and lower-middle-income (A3) countries. B. Future prevalence rate in high-income (B1), upper-middle-income (B2), and lower-middle-income (B3) countries. C. Future DALY rate in high-income (C1), upper-middle-income (C2), and lower-middle-income (C3) countries

Funding Statement

This paper was funded by The Project of State Key Laboratory of Radiation Medicine and Protection (No. GZK1202402); The Applied Basic Research Projects under the Suzhou Municipal Science and Technology Development Program (No. SYW2024002); The Multicenter Clinical Trial Program for Critical Illnesses in Suzhou (No. DZXYJ202404).