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Author Interview: Dr. Rod Taylor
The Impact of Dietary Salt on Mortality and Cardiovascular Disease:
Cochrane Review
Author Interview: Rod Taylor, MSc, PhD
Prof of Health Services Research
Peninsula College of Medicine & Dentistry, University of Exeter
6th July 2010
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Publication:
Author Interview: Rod Taylor, MSc, PhD
Reduced dietary salt for the prevention of cardiovascular disease
Taylor RS, Ashton KE, Moxham T, Hooper L, Ebrahim S.
Cochrane Database of Systematic Reviews 2011, Issue 7. Art.
No.: CD009217. DOI: 10.1002/14651858.CD009217
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What are the implications of your results?
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Our results do not mean that asking people to reduce their intake of salt is not a good thing – people should continue to strive to do this.
We believe our results suggest that individual-based (advice) strategies to reduce salt intake on their own are not as effective as we might hope and therefore we need to use population-based strategies such as the use of food labelling/traffic light systems on food packaging, continued policies of salt reduction in processed food, including bread, by industry, and reductions in salt in school, work canteens and restaurants.
Many of these population measures were advocated last year by NICE in its advice on prevention of cardiovascular disease. In parallel with implementing these multi-faceted measures, we also need more robust research to demonstrate that such measures are indeed effective in not only reducing salt, but that these changes are sustained and convert into improvements in long term health.
Our findings of a potential harmful effect of salt reduction in people in heart failure needs urgent follow up research in order to see if this finding is robust and whether current advice to reduce salt intake to these individuals should change.
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Were any of the findings unexpected?
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Our research (a systematic review and meta-analysis) brings together six randomized trials. It shows that while giving advice to members of the general public or people with moderately raised blood pressure to reduce their dietary salt intake (by ~50% of usual intake of 8-9g/d) appears to be effective in reducing blood pressure by a small amount in the short term (up to three years), there was no strong evidence of a reduction in deaths or risk of a heart attack or stroke.
In the only study in patients with heart failure, advice to reduce salt appeared to increase the risk of mortality compared to those receiving no such advice.
Our findings are actually consistent with salt restriction reducing death rates by as much as 42% or increasing death rates by 40%. This is because the studies, even taken together, are too small to make a definitive statistical
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What is the explanation for your results?
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Our findings should not be taken as evidence that reducing the amount of salt people eat is a bad idea.
We show, as have others, that advice to reduce salt does lead to reductions in blood pressure. But in people with normal blood pressure such reductions are small and in those with mild to moderate high blood pressure are not as great as the effect achieved by using medication.
The likely explanation for lack of any big effect on blood pressure and on deaths is that it is very difficult for individuals to stick to a low salt diet for many years. Indeed it is likely that participants in these studies initially followed advice to reduce salt, but were not able to maintain this in the long term which contributed to the lack of health benefit.
Unfortunately, these studies did not continue to follow up the dietary intake (or urinary output) of participants in the long term which means we cannot completely verify our hypothesis.
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Why are your results different to previous research findings (that show a clear health benefit of salt)?
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The main reason is to do with the type of evidence.
Previous studies have estimated the effect of salt reduction on blood pressure from observational (non-experimental) evidence such as comparisons of populations, or groups of individuals who choose to eat less salt vs. others who choose to eat normal or high levels of salt.
Such evidence gives much larger blood pressure reductions than we found in the evidence from randomized trials which have less problems of selection bias (i.e. those who choose to reduce their salt are more likely to have other positive health behaviours such as eating lower amounts of saturated fats and take regular exercise).
Using these large blood pressure reductions to predict the deaths and disease prevented by salt restriction provides estimates that are much greater than those we found.
However, our findings are consistent with these optimistic predictions of benefit because the amount of evidence available is too small to make a clear judgment.
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Abstract: |
Background
An earlier Cochrane review of dietary advice identified insufficient evidence to assess effects of reduced salt intake on mortality or cardiovascular events.
Objectives
1. To assess the long term effects of interventions aimed at reducing dietary salt on mortality and cardiovascular morbidity.
2. To investigate whether blood pressure reduction is an explanatory factor in any effect of such dietary interventions on mortality and cardiovascular outcomes.
Search strategy
The Cochrane Library (CENTRAL, Health Technology Assessment (HTA) and Database of Abstracts of Reviews of Effect (DARE)), MEDLINE, EMBASE, CINAHL and PsycInfo were searched through to October 2008. References of included studies and reviews were also checked. No language restrictions were applied.
Selection criteria
Trials fulfilled the following criteria: (1) randomised with follow up of at least six-months, (2) intervention was reduced dietary salt (restricted salt dietary intervention or advice to reduce salt intake), (3) adults, (4) mortality or cardiovascular morbidity data was available. Two reviewers independently assessed whether studies met these criteria.
Data collection and analysis
Data extraction and study validity were compiled by a single reviewer, and checked by a second. Authors were contacted where possible to obtain missing information. Events were extracted and relative risks (RRs) and 95% CIs calculated.
Main results
Seven studies (including 6,489 participants) met the inclusion criteria - three in normotensives (n=3518), two in hypertensives (n=758), one in a mixed population of normo- and hypertensives (n=1981) and one in heart failure (n=232) with end of trial follow-up of seven to 36 months and longest observational follow up (after trial end) to 12.7 yrs. Relative risks for all cause mortality in normotensives (end of trial RR 0.67, 95% CI: 0.40 to 1.12, 60 deaths; longest follow up RR 0.90, 95% CI: 0.58 to 1.40, 79 deaths) and hypertensives (end of trial RR 0.97, 95% CI: 0.83 to 1.13, 513 deaths; longest follow up RR 0.96, 95% CI; 0.83 to 1.11, 565 deaths) showed strong evidence of any effect of salt reduction. Cardiovascular morbidity in people with normal blood pressure (longest follow-up RR 0.71, 95% CI: 0.42 to 1.20, 200 events) or raised blood pressure at baseline (end of trial RR 0.84, 95% CI: 0.57 to 1.23, 93 events) also showed no strong evidence of benefit. Salt restriction increased the risk of all-cause death in those with congestive heart failure (end of trial relative risk: 2.59, 95% 1.04 to 6.44, 21 deaths). We found no information on participants health-related quality of life.
Authors' conclusions
Despite collating more event data than previous systematic reviews of randomised controlled trials (665 deaths in some 6,250 participants), there is still insufficient power to exclude clinically important effects of reduced dietary salt on mortality or cardiovascular morbidity in normotensive or hypertensive populations. Further RCT evidence is needed to confirm whether restriction of sodium is harmful for people with heart failure. Our estimates of benefits from dietary salt restriction are consistent with the predicted small effects on clinical events attributable to the small blood pressure reduction achieved.
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Featured Angina| Acute Coronary Syndrome and Heart Disease Interviews
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Highlights of Article by Dr. Erik Hess et of Mayo Clinic ;CIRCOUTCOMES 2012
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Chest pain is the 2nd most common reason patients come to EDs across the United States
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Initial testing – including information obtained from the history, physical exam, electrocardiogram, and cardiac troponin – identifies > 98% of heart attacks
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To avoid missing a diagnosis of heart attack or pre-heart attack symptoms, emergency physicians often admit patients to observation units or to the hospital for extensive diagnostic testing, including stress testing
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This results in false positive test results, unnecessary exposure to radiation, and unnecessary downstream procedures such as stent placement in arteries of the heart
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Decision aids are evidence-based tools designed to educate and engage patients in decisions regarding their care
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We hypothesized that patients who were educated regarding their future risk for a heart attack and engaged in the decision of whether to be admitted to the observation unit for stress testing or to follow-up with a Mayo Clinic heart doctor in the next 72 hours would have greater knowledge about their short-term risk for heart attack, be more aware of the management options, and choose less intensive approaches to evaluation
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We randomly assigned 204 patients who came to the ED with chest pain and were being considered for observation unit admission to the decision aid or to usual care
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Decision aid patients:
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Had greater knowledge regarding their short-term risk for a heart attack
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Less frequently decided to be admitted to the observation unit for stress testing
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Had 4 times greater engagement in the decision making process
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Had no adverse events within 30 days of the ED visit
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Take home points
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Patients want to be educated and engaged in decisions regarding their care
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Once properly informed and engaged in treatment decisions, patients often choose less intensive treatment options
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Integrated health systems like the Mayo Clinic in which physicians collaboratively work together to provide ER patients ready access to outpatient follow-up have potential to improve the value of Emergency care
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Glucose, Insulin and Potassium (“GIK”) TO MINIMIZE IMPACT OF HEART ATTACKS BEFORE PATIENTS GET TO THE HOSPITAL
Study puts life-saving drugs in the hands of paramedics, decreasing rate of cardiac arrest and death from heart attacks
CHICAGO (March 27, 2012) — Paramedics can potentially reduce someone’s chances of having a cardiac arrest or dying by 50 percent by immediately administering a mixture of glucose, insulin and potassium (“GIK”) to people having a heart attack, according to research presented today at the American College of Cardiology’s 61st Annual Scientific Session. The Scientific Session, the premier cardiovascular medical meeting, brings cardiovascular professionals together to further advances in the field.
The study showed that patients who received GIK immediately after being diagnosed with acute coronary syndrome — which indicates a possible heart attack is either in progress or on the way — were 50 percent less likely to have cardiac arrest (a condition in which the heart suddenly stops beating) or die than those who received a placebo, although the treatment did not prevent the heart attack from occurring. The reduction in in-hospital cardiac arrest or death was a “secondary endpoint”, so statistically was not definitive, but was consistent with how GIK seems to work in experimental models of heart attack.
The effect was also present for patients with ST-elevation heart attacks, which require immediate treatment. For those patients, immediate GIK was associated with a 60 percent reduction in in-hospital cardiac arrest or death.
“When started immediately in the home or on the way to the hospital — even before the diagnosis is completely established — GIK appears not completely prevent any heart attack from occurring, but appeared in this trial to reduce the size of heart attacks and to reduce by half the risk of having a cardiac arrest or dying,” said Harry P. Selker, MD, MSPH, executive director of the Institute for Clinical Research and Health Policy Studies at Tufts Medical Center, who led the study with Joni Beshansky, RN, MPH, co-principal investigator and project director. “Acute coronary syndromes represent the largest cause of death in this country. GIK is a very inexpensive treatment that appears to have promise in reducing those deaths and morbidity.”
The cost of the treatment is about $50.
“Because the trial is the first to show GIK could be effective when used by paramedics in real-world community settings, it could have important implications for the treatment of heart attacks,” Dr. Selker said. Previous clinical trials have shown no consistent effect, likely because the GIK was given too late to help. This study, the “IMMEDIATE Trial,” was the first to test the effectiveness of administering GIK at the very first signs of a threatening heart attack, in the community, rather than waiting hours until the diagnosis was well-established at a hospital, as done in previous clinical trials.
“We wanted to do something that is effective and can be used anywhere,” said Dr. Selker. “We’ve done a lot of studies of acute cardiac care in emergency departments and hospitals, but more people die of heart attacks outside the hospital than inside the hospital. Hundreds of thousands of people per year are dying out in the community; we wanted to direct our attention to those patients.”
The researchers trained paramedics in 36 Emergency Medical Services systems in 13 cities across the country to administer GIK after determining that a patient was likely having a threatened or already established heart attack using electrocardiograph-based ACI-TIPI (acute cardiac ischemia time-insensitive predictive instrument) and thrombolytic predictive instrument decision support that prints patient-specific predictions on the top of an electrocardiogram. The paramedics used these predictions to decide if a patient would likely benefit from treatment. There were 911 patients randomized to receive either the GIK treatment or a placebo.
Administering GIK immediately also reduced the severity of the damage to the heart tissue from the heart attack. On average, 2 percent of the heart tissue was destroyed by the heart attack in people receiving GIK, compared with 10 percent in those who received the placebo. Although a significant proportion of suspected heart attacks are later determined to be false alarms (23 percent in this study), administering GIK does not appear to cause any harmful effects in such patients.
The research team will follow up with study participants at six and 12 months to evaluate the longer-term benefit of the GIK treatment.
This study was funded by the NIH’s National Heart, Lung and Blood Institute.
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Amazon.com 's Editorial Reviews
Angina: New Ways to Treat
Chronic Chest Pain
Part of the award winning public television series Healthy head
/Healthy Mind. It's one of the scariest medical symptoms for people who are generally healthy: a tightening, painful feeling in the chest known as Angina. In some cases this chest pain can be a serious warning that requires immediate treatment. But for the millions of people with chronic, stable angina the discomfort is something that can be readily managed with a variety of treatments. In this program we take a look at what generally causes angina, what can be done to prevent it and how it can be effectively treated with lifestyle changes, innovative drug therapies and medical procedures.
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Amazon.com Editorial Review:
Philips HeartStart Home Defibrillator (AED)
Be prepared for the unexpected.
When sudden cardiac arrest (SCA) strikes, the electrical system of the heart short circuits, causing the heart to quiver rather than pump in a normal rhythm. It typically results in the abnormal heart rhythm know as ventricular fibrillation (VF). It usually happens without warning and the majority of people have no previously recognized symptoms of heart disease. And it most often happens at home. For the best chance of survival from SCA caused by VF, a defibrillator should be used within 5 minutes. Yet, less than 1 in 20 people survive largely because a defibrillator does not arrive in time.
Just as seat belts or airbags do not save every life in a traffic accident, a defibrillator will not save every person who suffers a sudden cardiac arrest. Yet many lives could be saved if more people could be reached more quickly.
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