School-based programme to reduce dietary salt intake and blood pressure amongst adolescents and their parents: a cluster-randomised controlled trial in rural and urban Malawi
Abstract
Background: Excess dietary salt intake and high blood pressure are growing public health challenges in Africa, with limited evidence for effective interventions. We evaluated the effect of a school-based programme on salt intake and blood pressure of adolescents and their parents. Methods: We conducted a cluster-randomised controlled trial with 26 primary schools in rural and urban Malawi. All pupils aged 11-14 years and their parents were eligible. The intervention comprised lessons and activities delivered over one school term promoting reduced salt intake. Co-primary outcomes were change in adolescent salt intake and systolic blood pressure (SBP) at 3-months. Secondary outcomes were change in adolescent diastolic blood pressure (DBP), adult salt intake, and adult blood pressure at 3-months; and change in blood pressure of all participants at 12-months. Findings: We recruited 1968 participants between September 24th-October 13th 2019 and January 8th-24th 2020. Thirteen primary schools received the salt reduction programme (362 adolescents, 614 adults) and 13 the routine curriculum (362 adolescents, 596 adults). At baseline, mean urinary salt was 3.9g/day (SD 2.15) for adolescents and 4.3g/day (SD 2.50) for adults. Participation in the intervention was high, with overall compliance of 87% by adolescents. At 3-months, there was no significant difference in change in adolescent salt intake (-0.17g/day, 95% CI -0.63-0.29) or adolescent SBP (0.59mmHg, -1.80-2.97). There was also no significant difference in change in adult salt intake, or blood pressure at 3 or 12 months, except adolescent SBP at 12-months. Interpretation: A school-based salt reduction intervention was feasible and had high levels of engagement, but did not reduce salt intake or blood pressure of adolescents and adults over a 3-month period. Longer term implementation, complemented by broader strategy and policy engagement, may be needed for school-based approaches to achieve reductions in dietary salt and blood pressure. Funding: Medical Research Council Registration: ISRCTN13909759
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S., W., N., P., R., C. J., S., M., M., C., M., K., C., C., R., B., M., K., E., M., D., D. K., A., S., S., M. F., R., G. J., C., C. A., J., M. (2025). School-based programme to reduce dietary salt intake and blood pressure amongst adolescents and their parents: a cluster-randomised controlled trial in rural and urban Malawi. arXiv preprint arXiv:10.64898/2025.12.22.25340861.
Witek-McManus, S., Phiri, N., Carpenter, J. R., Munthali-Mkandawire, S., Chabwera, M., Katundulu, M., Chiphinga-Mwale, C., Burton, R., Kerac, M., McIntosh, E., Dembo Kangombe, D., Saka, A., Mair, F. S., Glynn, J. R., Crampin, A. C., and Masiye, J.. "School-based programme to reduce dietary salt intake and blood pressure amongst adolescents and their parents: a cluster-randomised controlled trial in rural and urban Malawi." arXiv preprint arXiv:10.64898/2025.12.22.25340861 (2025).