Global burden of male infertility
In Fig. 1, a gradual increase in the prevalence of male infertility, represented by the YLD number, was observed globally. The ASPR and ASYR also demonstrated an upward trend between 1990 and 2019, albeit with some fluctuations along the way (Fig. 1).
To examine the global prevalence, YLD, ASPR and ASYR of male infertility and their percentage changes, a comparison was made between the data from 1990 to 2019. The prevalence number of male infertility increased by 76.9%, from 31,952 thousand (95% UI: 18,089–50,104.9) in 1990 to 56,530.4 thousand (95% UI: 31,861.5–90,211.7) in 2019. The ASPR of male infertility rose from 1,179.22 per 100,000 population (95% UI: 671.86–1,866.05) in 1990 to 1,402.98 per 100,000 population (95% UI: 792.24–2,242.45) in 2019, reflecting a 19% increase since 1990 (Table 1).
In terms of YLD, the number of YLD increased from 181,947.9 (95% UI: 68,999.7–434,846.1) in 1990 to 321,829.1 (95% UI: 120,614.9–771,411.2) in 2019, indicating a 76.9% rise. Additionally, age-standardized YLD rates per 100,000 population grew from 6.68 (95% UI: 2.54–15.81) in 1990 to 7.99 (95% UI: 3.01–19.17) in 2019, representing a 19.6% increase (Table 2).
Regional burden of male infertility
To compare male infertility data between 1990 and 2019, we conducted a comprehensive analysis of the prevalence, YLD, ASPR and ASYR, along with their percentage changes, across 21 regions classified by geography in the GBD study. In 2019, East Asia exhibited the highest prevalence number of male infertility, with 14,936.8 thousand cases (95% UI: 7,597.5–25,349), while Australasia had the lowest, with 78.7 thousand cases (95% UI: 44.4–128.2). Notably, only two regions, Eastern Europe and High-income Asia Pacific, experienced a decrease in the prevalence number between 1990 and 2019. Examining the ASPR of male fertility in 2019, Western Sub-Saharan Africa recorded the highest value of 2,510.75 (95% UI: 1,403.12–3,987.3), followed by Eastern Europe with 2,199.48 (95% UI: 1,192.24–3,549.31) and East Asia with 1,825.6 (95% UI: 931–3,080.22). Conversely, Andean Latin America (518.07, 95% UI: 346.37–761.91), Australasia (567.84, 95% UI: 319.93–921.07) and High-income Asia Pacific (947.7, 95% UI: 517.47–1,581.34) exhibited the lowest ASPR values. Regarding the percentage change in ASPR from 1990 to 2019, Central Latin America observed the highest percent change at 62.8%, followed by Western Sub-Saharan Africa at 57.5%, and South Asia at 46.9%. Interestingly, three regions experienced a decrease in ASPR percentage change in 2019 (Central Sub-Saharan Africa, High-income Asia Pacific and Oceania), while ASPR increased in eighteen regions. Notably, two regions, Western Sub-Saharan Africa and Central Latin America, witnessed an increase in ASPR by over 50% (Table 1).
Similarly, in 2019, East Asia recorded the highest YLD number for male infertility, with 79,907.4 (95% UI: 27,700.9–197,873.1), followed by South Asia with 72,799.9 (95% UI: 26,722.8–170,871.3) and Southeast Asia with 30,350.2 (95% UI: 11,350–74,346.2). Notably, Western Sub-Saharan Africa exhibited the largest percentage change in YLD at 274.6%. On the other hand, only Eastern Europe (-10.1%) and High-income Asia Pacific (-8%) experienced a decrease in the percentage change, while the remaining nineteen regions showed an increase. Furthermore, in 2019, Western Sub-Saharan Africa had the highest ASYR per 100,000 population, with a value of 13.94 (95% UI: 5.13–32.3), followed by Eastern Europe with 12.84 (95% UI: 4.73–30.42) and East Asia with 9.8 (95% UI: 3.37–24.36). Conversely, Andean Latin America was the region with the lowest ASYR, with a value of 3.01 (95% UI: 1.18–6.66). Between 1990 and 2019, an increasing trend in ASYR was observed in eighteen regions, while only three regions, High-income Asia Pacific, Central Sub-Saharan Africa and Oceania, experienced a decrease in ASYR (Table 2).
National burden of male infertility
In Fig. 1, a gradual increase in the prevalence of male infertility, represented by the YLD number, In addition to regional analysis, this study also compared the data among 204 countries and territories in 2019. Among these countries and territories included in the GBD study, China exhibited the highest prevalence number of male infertility, with 14,577,432.6 (7,416,528.3–24,752,355.6), followed by India with 11,392,467.2 (6,258,342–184,672,22) and Indonesia with 2,873,683.7 (1,563,954.3–4,590,378.2) (Fig. 2A and additional file 1). Similarly, the ranking for YLD number mirrored the prevalence ranking, with China being the highest at 77,983.6 (27,050.6–193,046.6), followed by India with 66,172.3 (24,375.1–156,501.1) and Indonesia with 16,430.3 (6,021.4–39,065.8). Notably, Tokelau had the lowest YLD ranking, with a value of 0.1 (0-0.1) (Fig. 2 C and additional file 3). Examining the ASPR, the top five countries with the highest ASPR values were Cameroon with 3,159.02 (1,828.63–5,022.17), Guinea with 2,776.63 (1,556.16–4,588.61), Senegal with 2,685.8 (1,570.06–4,262.13), Liberia with 2,684.92 (1,473.85–4,402.04) and Mauritania with 2,658.04 (1,536.9–4,303.08) (Fig. 2B and additional file 2). Similarly, the top five countries with the highest ASYR values were Cameroon with 18.14 (6.73–42.12), Mauritania with 15.18 (5.77–35.62), Senegal with 15.16 (5.62–35.24), Guinea with 15.13 (5.35–35.78) and Liberia with 14.61 (5.25–33.95). Conversely, Pakistan had the lowest ASYR ranking, with a value of 2.06 (0.7–5.01) (Fig. 2D and Additional file 4).
Age pattern
When examining the prevalence and YLD of male infertility across different age groups through age stratification, we observed that the global prevalence number, prevalence rate, YLD number and YLD rate of male infertility reached their peak in the 30–34 year age group in 2019 (Fig. 3). In the prevalence age-stratified analysis, the number and rate of prevalence were comparable between the 25–29 and 35–39 year age groups (Fig. 3A). However, in the YLD age-stratified study, the number and rate of YLD were slightly higher in the 25–29 year age group compared to the 35–39 year age group (Fig. 3B). Notably, both the prevalence and YLD numbers of male infertility exhibited a significant reduction in the 40–45 year age group when compared to other age groups (Fig. 3).
Burden of male infertility by SDI
Figure 1 provides an overview of the temporal trends in the prevalence number, YLD number, ASPR and ASYR of male infertility from 1990 to 2019, categorized by different levels of SDI, including High SDI, High-middle SDI, Middle SDI, Low-middle SDI and Low SDI.
Over the study period, both the prevalence and YLD numbers in Middle SDI regions exhibited a gradual increase. The High-middle SDI regions closely followed the Middle SDI regions, with prevalence and YLD numbers consistently remaining at high levels. In contrast, the prevalence and YLD in High SDI regions remained relatively low. Notably, Middle SDI and High-middle SDI regions had the highest prevalence and YLD numbers, while High SDI and Low SDI regions had the lowest (Fig. 1A and B). In terms of ASPR and ASYR, the burden of male infertility in High-middle SDI and Middle SDI regions surpassed the global average. Conversely, the ASPR and ASYR of male infertility in High SDI, Low-middle SDI and Low SDI regions were lower than the global levels. However, it is important to highlight that the ASPR and ASYR of Low-middle SDI and Low SDI regions exhibited a significant increase after 2010. Furthermore, the ASPR and ASYR showed an increasing trend in all five SDI regions between 1990 and 2019. Among these regions, High-middle SDI had the highest values, while High SDI had the lowest. However, the patterns of change differed among the regions, with High-middle SDI displaying a continuous rise and Middle SDI, Low-middle SDI and Low SDI regions demonstrating a W-shaped pattern of change (Fig. 1C and D).
In our study, we examined the correlation between SDI and the corresponding ASPR and ASYR of male infertility in 21 regions covered by the GBD study, spanning the period from 1990 to 2019. Our analysis revealed an M-shaped relationship between SDI and the ASPR and ASYR of male infertility. At the regional level, the expected values displayed two peaks at SDI values of 0.4 and 0.7. Additionally, when the SDI value was 0.5, a slight decline was observed, followed by a subsequent increase. However, for SDI values greater than 0.7, the ASPR exhibited a substantial decreasing trend. During the study period, the ASPR and ASYR in Western Sub-Saharan Africa, East Asia, Eastern Europe, Oceania and the Caribbean were higher than the expected values based on their respective SDI levels. On the other hand, the ASPR and ASYR in Eastern Sub-Saharan Africa, North Africa and the Middle East, Southern Latin America, Andean Latin America and Australasia were lower than the expected values. Notably, in the early years, a lower burden of ASPR was observed in South Asia, Southeast Asia, Southern Sub-Saharan Africa, Western Europe, High-income Asia Pacific and High-income North America. However, it is important to highlight that in the latter years, the burden of ASPR increased in these regions. Overall, our findings suggest a complex relationship between SDI and the burden of male infertility, characterized by regional variations and changes over time (Fig. 4A and B).