Linear and non-linear dose-response analysis
Four of six studies on the association between total water intake and all-cause mortality were included in the dose-response analysis[6, 14-16] (Figure 5 ). We found a significant non-linear association (P-nonlinearity=0.01). Furthermore, linear dose-response meta-analysis revealed a significant inverse association between total water intake and all-cause mortality by an additional one cup per day (Pooled ES: 0.98; 95% CI: 0.97-0.99, P= 0.001) (Supplemental Figure 1 ).
In the dose-response analysis of total water intake and CVD mortality, based on four studies, out of six studies, we found a significant non-linear association (P-nonlinearity=0.009) (Figure 6 ). Based on linear dose-response analysis, each additional cup of total water intake per day was associated with a 3% lower risk of death from CVD (Pooled ES: 0.97; 95% CI: 0.96-0.98, P<0.001) (Supplemental Figure 2 ).