Temporal trends in the burden of UC in China and globally from 1990 to 2021

In 2021, the ASIR, ASPR, ASMR, and ASDR of UC in China were 6.65, 46.52, 1.24, and 37.86 per 100,000 individuals, respectively. Compared to 1990, the ASMR and ASDR in China decreased by 48.63% and 48.15%, while the ASIR and ASPR increased by 17.79% and 37.67%, respectively. Globally, the burden trend of UC was similar to that in China, with an increase in ASIR and ASPR and a decrease in ASMR and ASDR, although the magnitude of the increase and decrease was smaller than in China (Table 1).

Table 1 The changes in ASIR, ASPR, ASMR, and ASDR of UC in China and globally from 1990 to 2021 (per 100,000 individuals)

In China, approximately 500,700 cases of UC were estimated in 2021, including 72,000 new cases and 13,600 deaths, resulting in 405,500 DALYs. Compared to 1990, the CIR and CPR displayed an upward trend in 2021. Conversely, CMR and CDR exhibited a decreasing trend. On a global scale, all rates showed an increasing trend (Table S1).

We also compared the trends in the incidence, prevalence, mortality, DALYs, and corresponding ASRs of UC in China and globally over the years. As shown in Fig. 1 and Table S2, from 1990 to 2021, the incidence and prevalence of UC in China exhibited a pattern of initial increase, followed by a decrease, and then another increase (Fig. 1A, B). The turning points of peak incidence and prevalence occurred in 2011 and 2015, reaching new peaks in 2021. The number of deaths and DALYs attributed to UC in China followed a similar pattern, with turning points in 2005 and 2015/2016. The incidence, prevalence, mortality, and DALYs globally showed an overall steady increase.

Fig. 1

The number of incident cases and ASIR (A), the number of prevalent cases and ASPR (B), the number of mortality cases and ASMR (C), and the number of DALYs and ASDR (D) of UC in China and globally from 1990 to 2021

Regarding the trends in ASRs, the ASIR and ASPR of UC in China showed a pattern of initial increase, followed by a decrease, and then another increase (Fig. 1C, D). The turning points of peak ASIR and ASPR occurred in 2008 and 2016. The ASMR and ASDR of UC in China exhibited a pattern of initial decrease, followed by an increase, with a turning point in 2017, and a slight upward trend in 2021. Additionally, the ASIR and ASPR of UC globally showed a slow upward trend, while the ASMR and ASDR generally displayed a pattern of initial decrease, followed by an increase, and then a decrease again, with the lowest values observed in 2014.

Joinpoint regression analysis results

Next, we examined the specific trends in ASRs of UC in China and globally from the Joinpoint regression analysis results for the period 1990–2021. The results indicate that over these 32 years, the overall trend for the ASIR and ASPR of UC in both China and globally has been increasing (Fig. 2A, B). The AAPC for ASIR in China was 0.57; globally, it was 0.5. The AAPC for ASPR in China was 1.09, while globally it was 0.69. The AAPC in ASIR and ASPR of UC in China was higher than the global average. Furthermore, the APC for each year in China reached its highest point in 2010 and gradually decreased, reaching its lowest point in 2016, and then showed an upward trend. In contrast, the global APC peaked in 2018 and showed a decreasing trend since then.

Fig. 2

Joinpoint regression analysis of ASRs for UC in China and globally from 1990 to 2021. A ASIR. B ASPR. C ASMR. D ASDR. APC* denoted significant p-values (< 0.05), indicating statistically significant changes in APC

Regarding ASMR and ASDR, the overall trend for China and global UC decreased (Fig. 2C, D). The AAPC for ASMR in China was − 2.11, while globally it was − 0.69. The AAPC for ASDR in China was − 2.08, while globally it was − 0.68. The AAPC in ASMR and ASDR of UC in China was higher in the downward direction compared to the global average. Additionally, it is noteworthy that the ASMR and ASDR of UC in China showed an upward trend after 2018, while globally they showed a decreasing trend.

Trends in UC burden by age group in China and globally in 1990 and 2021

In Fig. 3, we present a comparison of the number of incidences, prevalence, mortality, and DALYs, and CIR, CPR, CMR, and CDR of UC in different age groups in China and globally in 1990 and 2021. For more detailed data, please refer to Table S3. From Fig. 3A, B, it could be observed that the incidence and prevalence of UC in China and globally, as well as the corresponding CRs (CIR and CPR), showed a pattern of initial increase followed by a decrease with increasing age. Moreover, in 2021, the incidence, prevalence, and CRs in each age group were generally higher than those in 1990. In terms of specific age groups, the greatest number of incidence (13,986) and prevalence (107,904) for UC in China was in the 55–59 age group, which increased by 204.84% and 242.99% respectively compared to 1990. In contrast, in 2021, the greatest number of incidence (79,324) and prevalence (617,926) for global UC was in the 60–64 age group, which increased by 146.67% and 158.59% respectively compared to 1990.

Fig. 3

Comparison of the number of incident cases and ASIR (A), comparison of the number of prevalent cases and ASPR (B), comparison of the number of mortality cases and ASMR (C), comparison of the number of DALYs and ASDR (D) of UC in different age groups in China and globally between 2021 and 1990

From Fig. 3C, D, it could be observed that the number of mortality and DALYs of UC in China and globally showed a pattern of initial increase followed by a decrease with increasing age. The overall trend for the CMR and CDR of UC in China and globally was an initial increase followed by a decrease. Additionally, compared to 2019, the CMR and CDR of UC in each age group in 2021 were lower. Specifically, in China, the highest number of deaths (2,227) due to UC was in the 65–69 age group, which increased by 54.33% in 2021 compared to 1990. The greatest number of cases (67,751) in the 55–59 age group increased by 27.21% in 2021 compared to 1990. For global UC, the greatest number of deaths (15,671) and DALYs (418,106) was in the 65–69 age group, which increased by 79.07% and 83.86% respectively compared to 1990.

Forecast of UC burden in China and globally from 2022 to 2035

Finally, we conducted Bayesian Age-Period-Cohort (BAPC) analysis to forecast the number of incidences, prevalence, mortality, and DALYs of UC in China and globally from 2022 to 2035, as well as the corresponding trends in ASIR, ASPR, ASMR, and ASDR. The results are presented in Fig. 4 and Table S4. The projected incidence, prevalence, mortality, and DALYs of UC in China and globally are expected to increase over the next 15 years. On a global scale, ASIR, ASPR, ASMR, and ASDR showed a declining trend. In contrast, in China, ASIR, ASPR, ASMR, and ASDR exhibited an upward trend. It is estimated that by 2035, the global UC incidence, prevalence, and mortality will reach approximately 621,400, 4,369,100, and 128,700, respectively, with DALYs count of approximately 3,157,200. In China, the projected UC incidence, prevalence, and mortality by 2035 will reach approximately 136,800, 887,600, and 24,000, respectively, with DALYs count of approximately 621,400. Furthermore, when examining the annual data of UC ASRs from 2022 to 2035, it is evident that the growth rates of ASIR, ASPR, ASMR, and ASDR in China are significantly higher than the global average over the next 15 years.

Fig. 4

Temporal trends of the number of incidences, prevalence, mortality, DALYs, and ASIR, ASPR, ASMR, and ASDR of UC in China and globally from 1990 to 2035. The dashed lines represent the predicted values, while the solid lines represent the observed values in the GBD dataset. The vertical dashed line indicates the starting point of the predictions. A ASIR; B ASPR; C ASMR; D ASDR

5 Association between the burden of UC and SDI in China and globally from 1990 to 2021

We explored the association between the burden of UC and SDI in China and the world from 1990 to 2021 in Fig. 5 and Table S5. According to the results, there was a significant positive correlation between ASIR, ASPR of UC and SDI in China and the world (P < 0.05). However, there was a significant negative correlation between ASMR, ASDR and SDI in UC in China and globally (P < 0.001). In terms of the strength of correlation, the correlation between the burden of UC and SDI was heavier in the world than in China.

Fig. 5

Association of ASIR (A), ASPR (B), ASMR (C), ASDR (D) with SDI in UC in China and globally from 1990 to 2021

Changes in ASMR and ASDR of UC attributed to high BMI in China and globally in 1990 and 2021

In subsequent research, we identified the risk factors influencing the mortality and DALYs of UC in China and globally and found that only high BMI was a significant factor. We further analyzed the changes in ASMR and ASDR of UC attributed to high BMI in China and globally in 1990 and 2021, as shown in Table 2. Compared to 1990, the ASMR of UC attributed to high BMI in China increased by 19.46% in 2021, and the ASDR increased by 20.86%. For global UC attributed to high BMI, the ASMR increased by 8.30% in 2021, and the ASDR increased by 11.42%. Overall, the increase in ASMR and ASDR of UC attributed to high BMI in China was greater than the global average.

Table 2 Changes in UC ASMR and ASDR due to High BMI factors in China and globally from 1990 to 2021