Subgroup, sensitivity analyses, and publication bias:
To test the robustness of the results and investigate the between-study heterogeneity, we conducted subgroup analyses. Supplemental Table 3 presents findings for the different subgroups. In terms of total water intake and risk of all-cause mortality, a significant inverse association was obtained in studies conducted in US countries. However, a significant positive association was seen in studies conducted in US countries and those that had applied food recall or record for total water intake assessment. In terms of total water intake and risk of CVD mortality a significant inverse association was seen in studies that conducted in US and non-US countries, those that performed in females and males, studies that had used FFQ for total water intake assessment, studies with a >10 years follow-up duration and those that controlled for BMI and energy intake in their analysis. In terms of drinking water intake and all-cause mortality, a significant inverse association was reached in studies that had applied FFQ for drinking water assessment.
Findings from the sensitivity analysis using a fixed-effects model revealed that the exclusion of any single study from the analysis did not appreciably alter the pooled effect sizes. There were no missing studies imputed in regions of the contour enhanced funnel plots. No publication bias was found based on Egger’s linear regression test. The application of the trim and fill method did not change the average effect size, further suggesting that results were not affected by publication.