Sustained Effects of a Scaled-Up mHealth and School-Based Intervention for Salt Reduction (EduSaltS) in Schoolchildren and Their Families: 1-Year Follow-Up of a Cluster Randomized Controlled Trial

<b>Background</b>: While the mHealth and school-based scale-up intervention for salt reduction (EduSaltS) effectively reduced salt intake and blood pressure among adults living with participating schoolchildren, the sustainability of these effects remains uncertain. This study aimed to evaluate whether these effects persisted one year post intervention. <b>Methods</b>: A one-year follow-up of a cluster randomized controlled trial was conducted, involving 524 children and their 524 adult family members from 20 primary schools. At 24 months, 509 children (97.1%) and 486 adults (92.7%) completed the assessment. Mixed linear models were used to analyze the difference in changes in salt intake between the intervention and control groups at 24 months, compared to baseline and 12 months, as measured by consecutive 24 h urinary sodium excretions. Secondary outcomes included the differences in changes in blood pressure and salt-related knowledge, attitudes, and practices (KAP) scores. <b>Results</b>: The adjusted mean difference in changes in salt intake between groups was -0.34 g/24 h (95% CI: -0.94 to 0.26, <i>p</i> = 0.265) for children and -0.72 g/24 h (95% CI: -1.48 to 0.05, <i>p</i> = 0.065) for adults at 24 months versus baseline. The corresponding differences from 12 to 24 months were -0.09 g/24 h (95% CI: -0.69 to 0.51, <i>p</i> = 0.775) for children and 0.29 g/24 h (95% CI: -0.50 to 1.08, <i>p =</i> 0.468) for adults. The adjusted difference in changes in adult blood pressure showed a slight, nonsignificant rebound at 24 months. The intervention group maintained significantly higher KAP scores than the control group at both 12 and 24 months. <b>Conclusions</b>: The effects of EduSaltS on reducing salt intake and blood pressure in adults diminished slightly one year after the intervention ended. However, sustained improvements in salt-related KAP were observed in both children and adults. Ongoing support is vital to sustain long-term salt-reduction behaviors.