The global disease burden attributable to unsafe water, sanitation, and handwashing with unqualified facilities from 1990 to 2019.

Background: Water, sanitation, and hygiene (WaSH) are crucial determinants of human health. However, the spatio-temporal trends in the global burden of disease attributable to unsafe WaSH remain poorly understood. This study aimed to estimate the disease burden attributable to unsafe WaSH from 1990 to 2019 using data from the Global Burden of Disease (GBD) Study 2019, providing new insights into the associated health conditions. Methods: We extracted data on deaths and disability-adjusted life years (DALYs) attributable to unsafe WaSH from 1990 to 2019 from the GBD 2019. The disease burden was evaluated by region, sociodemographic index (SDI), sex, age, risk factor, and specific disease. Results: Globally, unsafe WaSH was responsible for 1 656 887.37 (95% uncertainty interval (UI) = 1 198 864.94, 2 312 688.33) deaths in 2019, a 49% decrease from 1990. The global age-standardised DALY rate due to unsafe WaSH was 1244.29 (95% UI = 993.20, 1544.13) per 100 000 in 2019, a 66% reduction since 1990. Western sub-Saharan Africa had the highest age-standardised death rate (ASDR) and age-standardised DALY rate in both 1990 and 2019. Among the 21 regions studied, only high-income North America witnessed an increasing ASDR from 1990 to 2019. Countries and territories in low SDI regions had higher ASDRs and age-standardised DALY rates. U-shaped associations were observed between the estimated annual percentage change (EAPC) of ASDR, EAPC of age-standardised DALY rate, and SDI. Both rates were slightly lower in females, with the burden concentrated in those under five and over 80 years old. In 2019, unsafe water source and diarrhoeal diseases remained the leading risk factor and cause of unsafe WaSH-related disease burden, respectively. Conclusions: Despite substantial improvements in hygiene awareness and health education, unsafe WaSH persists as a significant global health risk and a major contributor to the burden of diarrhoeal diseases. Disparities across regions and age groups remain evident. Increased efforts are needed to raise awareness and strengthen water and sanitation infrastructure, particularly in low SDI settings, to mitigate the health risks associated with unsafe WaSH.