NoToNa: Tackling cardiovascular risk in the adolescent life-course through a schools' salt-reduction intervention in sub-Saharan Africa

High blood pressure, which can lead to strokes, heart disease and kidney disease, is an increasing problem in sub-Saharan Africa, and starts young. Excessive salt intake is a major contributor to this. In some countries salt intake has been tackled through regulation of the processed food industry, but in much of sub-Saharan Africa little processed food is eaten and most salt is added at home. In Malawi we already have evidence of worrying levels of high blood pressure in teenagers, and high salt consumption.

Working with the School Health and Nutrition Programme, we propose to conduct a trial of an intervention package in schools in rural and urban Malawi which aims to reduce salt consumption in adolescents and their families. Of 26 schools, half will be randomized to receive the intervention and half will receive the normal school curriculum. The intervention will take place over one school term and will be delivered to children in Year 6. It will include lectures, discussions, homework including food diaries, competitions, drama and family quizzes. It is modelled on a successful intervention in China, and will be adapted for local use.

We will measure the effect of the intervention by measuring salt excretion (in urine) and blood pressure in a random sample of 20 children per school and their parents/guardians. We will compare the change in measurements from baseline to end of the intervention in participants from intervention and control schools, and will measure again at one year to assess the persistence of any effects of behaviour change. We will also assess factors that have helped or hindered implementation of the intervention, and will measure cost-effectiveness. This will be very important in deciding whether and how to scale up the intervention.

Hypertension, a risk factor for strokes, cardiovascular and renal disease, is increasing in sub-Saharan Africa, and starts young. WHO has identified salt reduction as one of the "best buys" to reduce cardiovascular disease in low income countries. In much of sub-Saharan Africa most sodium intake is from salt added at home, so measures tackling processed food that have worked elsewhere would have little impact. In Malawi we have already found hypertension in teenagers (5.1% males and 2.3% females aged 18-19) with levels increasing rapidly with age. Salt consumption is high: more than half of the adults exceeded recommended limits from plain salt alone.

Working with the School Health and Nutrition Programme, we propose to conduct a cluster-randomized trial of an educational/behavioural intervention package in schools in rural and urban Malawi which aims to reduce salt consumption in adolescents and their families. Of 26 schools, half will be randomized to receive the intervention and half will receive the normal school curriculum. The intervention will take place over one school term and will be delivered to children in Year 6 (aged 11-14). It will include lectures, discussions, homework including food diaries, competitions, drama and family quizzes. It is modelled on a successful intervention in China, and will be adapted for local use.

We will measure the effect of the intervention by measuring 24-hour urinary sodium and blood pressure in a random sample of 20 children per school and their parents/guardians at baseline, at the end of the intervention, and one year later (to assess persistence of any effects). We will compare the change in measurements from baseline in participants from intervention and control schools. Process evaluation will include identifying barriers and facilitators to the intervention, and we will also estimate cost-effectiveness. These factors will be critical in deciding whether and how to scale up the intervention.

The project could have substantial impact both for its empirical findings, and their potential to change the health and lifestyle on a large scale, and in methodological terms.
Excessive salt intake as a cause of high blood pressure is a huge and increasing problem. Few studies have assessed how to reduce it in sub-Saharan Africa. A cost-effective and scaleable intervention is needed, and a school-based intervention could be both easily scaleable and relatively cheap.
If successful this intervention could reduce hypertension (and therefore the risk of stroke, cardiovascular and renal disease) not only of the adolescents but of their families. Embedded social science and economics studies will enable us to establish how best to implement it and make it cost effective. Because we work closely with the School Health and Nutrition programme (a joint Ministry of Health and Ministry of Education, Science and Technology initiative) who are committed to developing healthy eating programmes, the potential to scale the intervention up across the country is immediately there. If the programme became part of the curriculum it would reinforce the learning in households and the community.
Many other areas of Africa have similar diets, and the programme could be implemented more broadly. Because the diseases it helps to prevent are common and costly the impact could have economic and social impacts as well as the direct impact on health.
Understanding and evaluating behavioural interventions such as this requires a multidisciplinary team to integrate the cluster randomized trial with qualitative and economic measurements. The trial will help build capacity for assessing complex interventions and implementation science. Furthermore, now that primary school enrolment is high in most countries, at least initially, the potential for delivering other health interventions through schools could be explored.