Salt reduction lowers cardiovascular risk: meta-analysis of outcome trials

FJ He, GA MacGregor - The Lancet, 2011 - thelancet.com
FJ He, GA MacGregor
The Lancet, 2011thelancet.com
A recent Cochrane Review by Rod Taylor and colleagues, published simultaneously in The
Cochrane Library1 and the American Journal of Hypertension2, stated in the plain language
summary that “Cutting down on the amount of salt has no clear benefits in terms of likelihood
of dying or experiencing cardiovascular disease”. 1 The Cochrane Library's own press
release headline included this statement:“Cutting down on salt does not reduce your chance
of dying”. 3 Both of these statements are incorrect. The study reported in the paper by Taylor …
A recent Cochrane Review by Rod Taylor and colleagues, published simultaneously in The Cochrane Library1 and the American Journal of Hypertension2, stated in the plain language summary that “Cutting down on the amount of salt has no clear benefits in terms of likelihood of dying or experiencing cardiovascular disease”. 1 The Cochrane Library’s own press release headline included this statement:“Cutting down on salt does not reduce your chance of dying”. 3 Both of these statements are incorrect. The study reported in the paper by Taylor and colleagues is a meta-analysis of randomised trials with follow-up for at least 6 months on the effect of reducing dietary salt on total mortality and cardiovascular mortality and events. 1, 2 There were seven trials with 6250 participants (665 deaths). One of these trials in heart failure, 4 in our view, should not have been included because the participants were severely salt and water depleted due to aggressive diuretic therapy (frusemide 250–500 mg twice daily, and spironolactone 25 mg per day) as well as captopril 75–150 mg per day and fluid restriction to 1000 mL per day. 4 While on these treatments, participants were randomly assigned to a reduced salt intake or their usual salt intake. 4 In view of the fact that the dose of diuretics was not adjusted downwards, a lower salt intake is likely to worsen the salt and water depletion and therefore, unsurprisingly, resulted in worse outcomes. In the remaining six trials, there is a reduction in all clinical outcomes (all-cause mortality, cardiovascular mortality and events)(table), although none of these are statistically significant. This trend of consistent reductions in all clinical outcomes seems to have been overlooked by Taylor and colleagues. 1 The non-significant findings are most likely the result of a lack of statistical power, particularly as Taylor and colleagues analysed the trials for hypertensives and normotensives separately. We have reanalysed the data by combining data for hypertensives and normotensives together. Our results show that there is now a significant reduction in cardiovascular events by 20%(p< 0· 05)(figure) and a non-significant reduction in all-cause mortality (5–7%), despite the small reduction in salt intake of 2· 0–2· 3 g per day. The results of our reanalysis, contrary to the claims by Taylor and colleagues, support current public health recommendations to reduce salt intake in the whole population. Taylor and colleagues call for further large longterm randomised trials of salt reduction on clinical outcomes. 1, 2
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