Transcript The Global Burden of Disease attributable to excess salt intake

The Global Burden of Disease attributable to excess
estimating exposures and effects
salt
intake:
John Powles and Saman Fahimi
Department of Public Health and Primary Care, University of Cambridge, CB2 0SR
ntroduction
Adding salt to food is not part of our
evolutionary background and evidence
that it harms health is persuasive.
We are making the first global estimates
of health losses attributable to excess
salt intake as members of the Nutrition
and Chronic Disease Expert Group in
the current iteration of the Global
Burden of Disease, Injuries, and Risk
Factors (GBD) Study. Estimates of
burdens in 1990 and 2005, attributable
to a wide range of risk factors, are due
to be reported later this year
Materials and methods
1. Identified causal effects
 Direct: stomach cancer
 Mediated: usual systolic blood
pressure (sbp)
2. Analytic approach
 Comparative Risk Assessment
 Attributable, not avoidable risk i.e.
optimal exposure as counterfactual
with no modeling of temporal
transition.
3. Exposure estimation
 Age and sex specific estimates for
21 GBD Study regions using best
available data.
 Preferred: 24-hr urinary excretion
(assumed to be 0.9 * intake)
 Imputed where data missing
Methods (cont)
Methods (cont)
4. Effect estimation
Effect modification
i. Stomach cancer: World
Cancer Research Fund (WCRF)
meta-analysis1 (risk related to
intakes)

By sex: exposure levels adjusted to mean energy intake of both sexes

By race: slope adjusted for African ancestry (+3.5 mmHg at age 50 per 100 mmol of
daily urinary Na excretion) (2 RCTs)
Effects of changes in usual sbp and associated uncertainty propagated forward by
blood pressure group of the GBD Study to estimate outcomes attributable to higher
than optimal salt intakes.
Results (work is ongoing.)
Global sodium exposure , Central Europe as a sample GBD Study region.
ii. Usual sbp – mean and (interindividual) standard deviation (effect
related to urinary excretion)
Meta-analysis of sodium reduction
RCTs of >4 wks2, re-analysed for mean
effect by age. Assumed linear down to
optimal exposure. Common to both
sexes (for energy adjusted exposures).
Conclusions
(Provisional)
Preparing central estimates of the
GBD attributable to higher than
optimal sodium intakes is feasible.
The most difficult outstanding
challenge is estimating the
uncertainty around these estimates.
Literature cited
1. World Cancer Research Fund / American Institute for
Cancer Research. Food, Nutrition, Physical Activity, and the
Prevention of Cancer: a Global Perspective. Washington,
DC: American Institute for Cancer Research; 2007.
2. He FJ, MacGregor GA. Effect of modest salt reduction on
blood pressure: a meta-analysis of randomized trials.
Implications for public health. J Hum.Hypertens. 2002
Nov;16(11):761-70.
Acknowledgments
We thank members of Nutrition and Chronic
Disease of the GBD Study expert panel (D.
Mozzaffarin, M. Ezzati, R. Micha, G. Danaie),
and the advisory expert panel on salt and
chronic disease (G. MacGregor, P. Elliot, M.
Law, B. Neal, I. Brawn, and F. He.)