Abstract
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Introduction: Attempting to curb the rising epidemic
of hypertension, South Africa implemented legislation
in June 2016 mandating maximum sodium levels in a
range of manufactured foods that contribute
significantly to population salt intake. This natural
experiment, comparing two African countries with and
without salt legislation, will provide timely information
on the impact of legislative approaches addressing the
food supply to improve blood pressure in African
populations. This article outlines the design of this
ongoing prospective nested cohort study.
Methods and analysis: Baseline sodium intake was
assessed in a nested cohort of the WHO Study on
global AGEing and adult health (WHO-SAGE) wave 2
(2014–2015), a multinational longitudinal study on the
health and well-being of adults and the ageing process.
The South African cohort consisted of randomly
selected households (n=4030) across the country. Spot
and 24-hour urine samples are collected in a random
subsample (n=1200) and sodium, potassium,
creatinine and iodine analysed. Salt behaviour and
sociodemographic data are captured using face-to-face
interviews, alongside blood pressure and
anthropometric measures. Ghana, the selected control
country with no formal salt policy, provided a nested
subsample (n=1200) contributing spot and 24-hour
urine samples from the SAGE Ghana cohort (n=5000).
Follow-up interviews and urine collection (wave 3) in
both countries will take place in 2017 (postlegislation)
to assess change in population-level sodium intake and
blood pressure.
Ethics and dissemination: SAGE was approved by
the WHO Ethics Review Committee (reference number
RPC149) with local approval from the North-West
University Human Research Ethics Committee and
University of the Witwatersrand Human Research
Ethics Committee (South Africa), and University of
Ghana Medical School Ethics and Protocol Review
Committee (Ghana). The results of the study will be
published in peer-reviewed international journals,
presented at national and international conferences,
and summarised as research and policy briefs.