Global ISD incidence, prevalence, and YLDs cases and age-standardized rates
Firstly, looking at the incidence, the highest number of cases and incidence rates each year are for FSD, with 1,729,224,009 cases (95% CI: 1,562,709,709 to 1,894,666,053) and an incidence rate of 21,668.40 (95% CI: 19,601.19 to 23,729.17) in 2021. Next is BSD, with 880,831,364 cases (95% CI: 855,895,431 to 905,652,994) and an incidence rate of 11,295.90 (95% CI: 10,982.62 to 11,619.01). Lastly, VSD has 84,730,445 cases (95% CI: 82,132,966 to 87,586,946) and an incidence rate of 1126.25 (95% CI: 1090.92 to 1165.91) (Fig. 1, Supplementary Table 1, 2).
From the prevalence perspective, FSD continues to rank first, with 616,532,287 cases (95% CI: 558,724,637 to 679,274,726) and a prevalence rate of 7,789.55 (95% CI: 7,059.28 to 8,583.54) in 2021. Interestingly, VSD overtakes BSD, with 136,807,659 cases (95% CI: 133,155,771 to 140,724,829) and a prevalence rate of 1,781.31 (95% CI: 1,733.08 to 1,835.16), while BSD has 36,958,263 cases (95% CI: 36,139,205 to 37,765,496) and a prevalence rate of 473.98 (95% CI: 463.37 to 484.64).
Next, looking at YLDs, VSD rises to the first position in 2021, with 4,199,075 cases (95% CI: 2,671,027 to 6,261,658) and YLDs rate of 54.77 (95% CI: 34.83 to 81.77). FSD comes next, with 3,429,497 cases (95% CI: 1,407,894 to 7,044,259) and YLDs rate of 43.39 (95% CI: 17.79 to 89.10). Lastly, BSD has 334,915 cases (95% CI: 189,302 to 569,706) and YLDs rate of 4.21 (95% CI: 2.36 to 7.20).
Based on different age groups and sex, the incidence, prevalence, and YLDs age-standardized rates of ISD
We investigated the burden of ISD across different age groups. We found that the highest incidence and prevalence rates of BSD were in the age groups under 5 years [15,477.29 (95% CI: 14,648.09 to 16,383.16) and 659.44 (95% CI: 628.24 to 687.88)] and 85 + years [14,574.98 (95% CI: 13,639.95 to 15,556.13) and 617.29 (95% CI: 587.00 to 647.59)]. FSD had the highest incidence rate in the 85 + years group [106293.26 (95% CI: 86020.70 to 127854.16)] and the highest prevalence rate in the 80–84 years group [74971.40 (95% CI: 60950.50 to 92547.59)]. VSD had the highest incidence rate in the 5–9 years group [2836.71 (95% CI: 2654.08 to 3027.29)] and the < 5 years group [2469.72 (95% CI: 2332.09 to 2618.08)]. The highest prevalence rate for VSD was in the 5–9 years group [3671.01 (95% CI: 3431.43 to 3929.41)] and the 10–14 years group [2997.93 (95% CI: 2791.91 to 3214.98)] (Fig. 2, Supplementary Table 3)
From the perspective of YLDs, the highest YLDs for BSD were in the 70–74 years group [7.36 (95% CI: 4.68 to 11.30)] and the 65–69 years group [7.07 (95% CI: 4.49 to 10.73)]. For FSD, the highest YLDs were in the 85 + years group [178.96 (95% CI: 70.52 to 372.25)] and the 80–84 years group [121.40 (95% CI: 49.71 to 252.06)]. VSD had the highest YLDs in the 5–9 years group [114.98 (95% CI: 70.54 to 174.82)] and the 10–14 years group [93.52 (95% CI: 59.81 to 141.17)]. This indicates that children and the elderly bear the greatest burden of ISD.
From a gender perspective, we found significant gender differences in the burden of ISD. The incidence rates of BSD and FSD were higher in males than females, while VSD showed no difference. In terms of prevalence rates and YLDs, males had higher rates for FSD and VSD compared to females, while BSD showed no difference. This suggests that males may be more prone to BSD, but the burden of FSD and VSD is greater (Fig. 3, Supplementary Table 4).
The global trends in ISD age-standardized prevalence rate based on Joinpoint regression from 1990 to 2021
To explore the global trends in ISD, we utilized Joinpoint regression (Fig. 4, Table 1). The results indicate significant increases in the prevalence rates of BSD and FSD compared to 1990, while VSD shows a significant decrease. BSD increased from 390.90 (95% CI: 382.23 to 398.80) in 1990 to 474.00 (95% CI: 463.37 to 484.64) in 2021, with no apparent turning points in the growth trend. FSD increased from 7350.13 (95% CI: 6652.51 to 8063.66) in 1990 to 7810.79 (95% CI: 7059.28 to 8583.54) in 2021. The growth rate slowed down from 1990 to 2005 [APC1990-2005: 0.264 (95% CI: 0.2599 to 0.2681), p = 0.000], then further slowed from 2005 to 2016 [APC2005-2016: 0.1404 (95% CI: 0.1328 to 0.1479), p = 0.000]. The trend stabilized from 2016 to 2019 (p = 0.795), but showed an upward trend in 2019 [APC2019-2021: 0.2481 (95% CI: 0.1513 to 0.345), p = 0.000]. VSD decreased from 1829.18 (95% CI: 1763.21 to 1867.37) in 1990 to 1783.85 (95% CI: 1733.08 to 1835.16) in 2021. The rate of decrease slowed from 2006 to 2015 [APC2006-2015: -0.0132 (95% CI: -0.0148 to -0.0116), p = 0.000], then slightly increased from 2015 to 2019 [APC2015-2019: 0.0333 (95% CI: 0.0259 to 0.0407), p = 0.000], followed by a rapid decrease after 2019 [APC2019-2021: -0.0287 (95% CI: -0.0435 to -0.0139), p = 0.001].
Table 1
The prevalence of ISD and their AAPC from 1990 to 2021 in the global.
Cause | 1990 number | 2021 number | 1990 rate | 2021 rate | AAPC | p |
BSD | 20733396 | 36958263 | 390.68 | 473.98 | 0.6235 (0.6143 to 0.6326) | 0.000 |
FSD | 367581342 | 616532287 | 7334.21 | 7789.55 | 0.1924 (0.1813 to 0.2034) | 0.000 |
VSD | 100377653 | 136807659 | 1812.95 | 1781.31 | -0.0566 (-0.0589 to -0.0542) | 0.000 |
Firstly, focusing on BSD, the highest prevalence rates were observed in Equatorial Guinea [1116.85 (95% CI: 1074.47 to 1157.89)], Gabon [1115.54 (95% CI: 1077.11 to 1157.18)], and Congo [1109.07 (95% CI: 1069.75 to 1148.85)]. The fastest growth rates were seen in Taiwan ,China [AAPC: 0.3961 (95% CI: 0.3868 to 0.4054), p = 0.000] and American Samoa [AAPC: 0.3943 (95% CI: 0.3733 to 0.4153), p = 0.000], while the most significant declines occurred in China [AAPC: -0.1057 (95% CI: -0.1152 to -0.0963), p = 0.000] and Italy [AAPC: -0.1163 (95% CI: -0.1397 to -0.0928), p = 0.000] (Fig. 5, Supplementary Table 5, 6).
Next is FSD, with the highest prevalence rates in Mali [23696.61 (95% CI: 20972.72 to 26338.73)], Ethiopia [23086.22 (95% CI: 20202.85 to 25968.55)], and Nigeria [20826.82 (95% CI: 18579.08 to 23380.75)]. The fastest growth rates were observed in Mexico [AAPC: 0.369 (95% CI: 0.3613 to 0.3766), p = 0.000] and Kenya [AAPC: 0.1747 (95% CI: 0.1075 to 0.2419), p = 0.000], while the most significant declines were seen in Equatorial Guinea [AAPC: -0.6248 (95% CI: -0.6382 to -0.6114), p = 0.000] and Rwanda [AAPC: -0.6315 (95% CI: -0.6652 to -0.5977), p = 0.000].
Lastly, for VSD, the highest prevalence rates were observed in Germany [4469.80 (95% CI: 4305.02 to 4639.21)], United States of America [4218.77 (95% CI: 4153.97 to 4281.10)], and Canada [4104.45 (95% CI: 3961.14 to 4253.45)]. The fastest growth rates were seen in Equatorial Guinea [AAPC: 0.4848 (95% CI: 0.4774 to 0.4923), p = 0.000] and Mexico [AAPC: 0.4347 (95% CI: 0.4309 to 0.4384), p = 0.000], while the most significant declines were observed in Ethiopia [AAPC: -0.0334 (95% CI: -0.0354 to -0.0315), p = 0.000] and United States of America [AAPC: -0.0655 (95% CI: -0.0691 to -0.0618), p = 0.000].
Initially, we conducted a correlation analysis between prevalence rates and SDI and found that BSD and FSD exhibited a negative correlation with SDI, while VSD showed a positive correlation (Fig. 6). This was further validated in the subsequent cross-national inequality analysis. Concentration indices and slope indices indicated that the populations affected by BSD and FSD were predominantly concentrated in low SDI regions (with concentration indices greater than 0 and coefficients of the slope index less than 0), whereas VSD was mainly concentrated in high SDI regions (with concentration indices less than 0 and coefficients of the slope index greater than 0).
Compared to 1990, the cross-national disparities in prevalence rates narrowed for BSD [-3.38 (95% CI: -4.12 to -2.65) and − 2.76 (95% CI: -3.52 to -1.99)] and FSD [-43.21 (95% CI: -50.74 to -35.68) and − 37.12 (95% CI: -44.62 to -29.62)], while the disparity increased for VSD [18.56 (95% CI: 9.63 to 27.49) and 21.17 (95% CI: 12.65 to 29.70)] by 2021 (Fig. 7, Supplementary Table 7).