The effect of water source on cognitive functioning in Chinese adults: A cross-sectional and follow-up study

The effect of water source on cognitive functioning is poorly understood. The present study explored the associations between water source and cognition in 9921 participants from the China Health and Retirement Longitudinal Study (CHARLS). Cognitive functioning was measured from three aspects: orientation and attention, episodic memory, and visuo-construction. Water sources included tap and non-tap water. Generalized linear models and multiple logistic regression models were conducted to investigate the associations of cognitive scores with water source among the whole population and different subgroups. Results from cross-sectional analysis reported that participants without access to tap water showed a lower cognitive score (β = - 0.57; 95% CI: - 0.74, - 0.39) than those with tap water as a water source; and this phenomenon was pronounced for both sexes and across all residences. During 4-years' follow-up, a greater decline of cognitive score was associated with no tap water use in the lowest quartile of baseline cognitive scores (β = - 0.67; 95% CI: - 1.26, - 0.08). Additionally, the utilization rate of tap water was lower in rural areas compared to urban areas. The lowest utilization rates were observed in urban areas of the Anhui province (0.38 in 2011 and 0.55 in 2015) and in rural areas of Inner Mongolia (0.09 in 2011 and 0.20 in 2015). These findings suggest that having no tap water may be a risk factor for cognition impairment, particularly for those with a low basic cognition score. Additionally, our results support the need to expand tap water use in China.