The impact of household wastewater on the frailty state of the elderly in China: based on a long-term cohort study in China

China’s household wastewater discharge has gradually increased, and its composition has become more complex, but the discharge treatment system is not perfect. At present, there is a lack of research on the impact of domestic wastewater on human health, especially on the frailty of the elderly. This study aimed to quantitatively assess the relationship between living wastewater and its main components and the frailty status of the elderly. The research data comes from the Chinese Longitudinal Healthy Longevity Survey (CLHLS), which consists of participants over 60 years old who participated in the three-wave survey in 2008, 2011, and 2014 and combined with domestic wastewater data in the statistical yearbook. A generalized estimating equation (GEE) model was used to assess the link between living wastewater and frailty status in the elderly. The single-pollutant model showed that there was a positive correlation between the discharge of household wastewater and the frailty of the elderly, OR (4.443), 95%CI (3.591, 5.498); ammonia nitrogen had a positive correlation with the frail state of the elderly, OR (4.527), 95%CI (3.587, 5.714); chemical oxygen demand (COD) had a negative association with whether the elderly are frail, OR (0.776), 95%CI (0.609, 0.988). After adjusting for covariates, there was still a positive correlation between household wastewater and the frailty of the elderly, OR (2.792), 95%CI (2.233, 3.492); a positive correlation between ammonia nitrogen and the frail state of the elderly, OR (2.894), 95%CI (2.284, 3.666). The association between COD and the frail state of the elderly, OR (0.823), 95%CI (0.640, 1.058), showed no correlation between the two. The results show that household wastewater may affect the health of the elderly, promote the occurrence of a frail state of the elderly, and increase the medical burden.