Global, regional, and national prevalence and trends of infertility among individuals of reproductive age (15–49 years) from 1990 to 2021, with projections to 2040

STUDY QUESTION: What is the prevalence and trend of infertility among individuals of childbearing age at global, regional, and national levels by sex and socio-demographic index (SDI) across 21 regions and 204 countries and territories? SUMMARY ANSWER: Our findings reveal a growing prevalence of infertility among individuals aged 15-49 years worldwide from 1990 to 2021, with an expected continued increase through 2040. WHAT IS KNOWN ALREADY: Infertility is a persistent global reproductive health issue, leading to significant societal and health consequences. No study has specifically described the current prevalence of infertility, its secular trend, or the variations between regions or countries with different SDI levels. STUDY DESIGN, SIZE, DURATION: A sex- and SDI-stratified systematic analysis of the prevalence of infertility across 21 regions and 204 countries and territories from 1990 to 2021 has been performed. PARTICIPANTS/MATERIALS, SETTING, METHODS: We retrieved data from the Global Burden of Disease Study (GBD) 2021 on the count and crude rate of infertility prevalence for individuals aged 15-49 years across 204 countries and territories from 1990 to 2021. In the GBD 2021 framework, infertility is defined as the absence of a live birth in a couple who have been in a union for at least 5 years and are actively trying to conceive, or in a couple who have been in a union for at least 5 years since their last live birth, with no use of contraceptives during this period. Estimated annual percent change was calculated to quantify the temporal trend in age-standardized prevalence rates (ASPRs) for infertility by sex, age, and SDI. The Bayesian age-period-cohort model was used to project the ASPRs from 2022 to 2040. MAIN RESULTS AND ROLE OF CHANCE: In 2021, an estimated 55 000 818 men and 110 089 459 women were living with infertility worldwide, corresponding to approximately 1820.6 cases per 100 000 population (1.8%) for males and 3713.2 cases per 100 000 population (3.7%) for females. Regionally, the highest infertility prevalence was observed in middle SDI regions, such as East and South Asia and Eastern Europe. Infertility primarily affected the age group of 35-39 years and females in most regions, with some notable exceptions. Between 1990 and 2021, the global ASPRs of infertility increased by an average of 0.49% (95% CI 0.34-0.63) for males and 0.68% (0.51-0.86) for females. Additionally, the fastest increase in female infertility occurred in high SDI regions, while the most significant rise in male infertility was seen in low-middle SDI areas. Furthermore, the global ASPR of male infertility is projected to rise more rapidly than that of female infertility from 2022 to 2040. LIMITATIONS, REASONS FOR CAUTION: The primary data sources for the infertility burden in the GBD 2021 are population-based surveys; however, less-developed regions often lack complete population-based statistics, leading to potential reporting bias of the infertility burden in these areas due to data sparsity and incompleteness. Additionally, this study could not separately assess the prevalence and trends of primary and secondary infertility. Furthermore, the GBD 2021 does not provide the attributable proportion of each cause of infertility; hence, we cannot compare the contribution of these causes to infertility by sex, age, and location. WIDER IMPLICATIONS OF THE FINDINGS: Sexual and reproductive health are crucial for individuals' health, economic development, and overall human wellbeing. It is essential for governments and the public to recognize the severity of infertility and prioritize the implementation of targeted interventions to enhance reproductive health. STUDY FUNDING/COMPETING INTEREST(S): This study was supported by the grants from the Science and Technology Project of Jiangmen (2020030103110009027). The authors have declared no conflict of interest. TRIAL REGISTRATION NUMBER: N/A.