The Global, Regional, and National Burden of Lower Respiratory Infections Caused by Streptococcus pneumoniae Between 1990 and 2021

<b>Aims</b>: To investigate the global epidemiological characteristics of lower respiratory infection (LRI) burden caused by <i>Streptococcus pneumoniae</i> (SP) from 1990 to 2021. <b>Methods</b>: Using data from the Global Burden of Disease (GBD) study 2021, we systematically analyzed <i>Streptococcus pneumoniae</i>-related (SP-related) LRI burden, focusing on mortality, disability-adjusted life years (DALYs), and temporal trends by age, gender, geographic region, and socio-demographic index (SDI) quintiles. Decomposition analysis assessed the influence of epidemiological shifts, population growth, and aging on age-standardized mortality rates (ASMRs), while an autoregressive integrated moving average (ARIMA) model projected future trends. <b>Results</b>: Between 1990 and 2021, the global SP-related LRI death number decreased from 1,028,083 (95% uncertainty interval (UI): 923,782-1,146,074) to 505,268 (95% UI: 454,335-552,539), and the ASMR dropped from 19.28 (95% UI: 17.32-21.49) to 6.40 (95% UI: 5.76-7.00) per 100,000. The age distribution consistently exhibited a clear two-tiered pattern, gradually shifting from being predominantly composed of young children to being dominated by older adults. Disparities were stark across SDI quintiles, low-SDI regions exhibited up to 100-times-higher under-five mortality than high-SDI regions. Geographic distribution showed the highest ASMRs in sub-Saharan Africa and the lowest in Canada, the United States, and Australia, with Mongolia and Finland showing the largest reductions in mortality. Epidemiological changes were the most significant factor in ASMR reduction. <b>Conclusions</b>: The SP-related LRI burden has decreased globally but remains a major health concern, especially in low-SDI regions. Targeted public health interventions, particularly for neonates and elderly adults, are essential to address persistent disparities and further reduce mortality.