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Cardiovascular Disease

Introduction 

Cardiovascular disease (CVD) is an umbrella term referring to strokes, coronary heart disease (CHD) and heart failure.

Stroke

A stroke occurs when part of the blood flow to the brain is cut off. This causes a break in the oxygen supply, causing cells to die. Stroke is the third most common cause of death in England and Wales(1), with an estimated 150,000 strokes and mini strokes(2) and 67,000 deaths from strokes every year (3). This equates to 9% of male and 13% of female deaths.(3)

Stroke has a greater disability impact compared to any other chronic disease. The outcomes of strokes are wide ranging, but sufferers can experience paralysis, speech impediment and memory problems which can be highly frustrating and difficult for both the individual and the family.  Over 300,000 people are living with moderate to severe disabilities as a result of stroke.(4) The direct cost of stroke to the NHS is estimated to be £2.8 billion.(5)

Coronary heart disease (CHD)

CHD is the term used to describe what happens when the heart’s blood supply is reduced or blocked. Raised blood pressure is a major risk factor for heart and circulatory diseases including heart attacks and heart failure. Over time, untreated high blood pressure can lead to a thickening of the heart muscle which can reduce the effectiveness of the heart pumping action.    

CHD is the UK's biggest killer, with one in every four men and one in every six women dying from the disease. In the UK, approximately 300,000 people have a heart attack each year.(6)

Who is most at risk of cardiovascular disease?

Older people, people with high blood pressure, diabetics, people of black and South Asian descent and smokers are all at increased risk of having a stroke or heart attack.

How does salt contribute?

Raised blood pressure is a major cause of cardiovascular disease, responsible for 62% of stroke and 49% of coronary heart disease. Importantly, the risk of CVD increases throughout the range of blood pressure, starting at 115/75 mmHg.(7) Salt is the major factor that increases blood pressure and is therefore responsible for many strokes and heart attacks every year.(8) From the blood pressure reduction seen in a meta-analysis (9), it was estimated that a reduction of 6 g of salt per day would reduce stroke by 24% and coronary heart disease by 18%. This would prevent approximately 35,000 stroke and CHD deaths a year in the UK and approximately 2.5 million deaths worldwide.(10)

In June 2010, the National Institute for Health and Care Excellence (NICE) published a report on the prevention of cardiovascular disease which highlighted salt reduction as the number one priority as a cardiovascular preventative measure. It also highlighted that we should be aiming for a salt intake of 6g by 2015 and 3g by 2025.(11)

Direct effect on stroke

Evidence suggests that a high salt intake also has a direct effect on strokes, independent of the effect of salt on blood pressure.(8,12-13) When different populations are compared, there is a very close correlation between salt intake and stroke mortality independent of blood pressure (Fig 2).(12) Another study has confirmed this within a single country.(8)

Current salt intake & dietary advice

Almost everyone in the UK (and the rest of the Western world) eats too much salt. The daily recommended amount in the UK is no more than 6 grams a day; the current average salt intake is 8.1g salt a day although many people are eating more than this.

It has been shown that a high salt intake, a low consumption of fruit and vegetables (which corresponds to a low potassium intake), obesity, excess alcohol intake and lack of physical exercise all contribute to the development of high blood pressure. However, the diversity and strength of the evidence is much greater for salt than for other factors. People with, or considered at risk, of stroke or heart disease should take extra care to ensure that they keep their salt intake below the recommended maximum of 6g.

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References

1. Wolfe C. “The Burden of Stroke" in Wolfe, C, Rudd, T and Beech, R (eds) Stroke Services and Research (1996) The Stroke Association
2. Office of National Statistics Health Statistics Quarterly (12) Winter 2001 "Stroke incidence and risk factors in a population based cohort study"; Scottish Stroke Care Audit 2005/2006.
3. British Heart Foundation, 2005. Coronary Heart Disease Statistics
4 Adamson, J et al. Stroke and Disability. Journal of Stroke and Cerebrovascular Diseases. 2004; 13 (4)
5. National Audit Office, 2005. Brain Damage: Faster access to better stroke care.
6. NHS (2009) Coronary Heart Disease. http://www.nhs.uk/Conditions/Coronary-heart-disease/Pages/Introduction.aspx
7. Lewington S et al. Age-specific relevance of usual blood pressure to vascular mortality: a meta-analysis of individual data for one million adults in 61 prospective studies. Lancet. 2002; 360, 1903-1913
8. Nagata C et al. Sodium intake and risk of death from stroke in Japanese men and women. Stroke. 2004; 35,1543-7
9. He FJ, MacGregor GA. Effect of modest salt reduction on blood pressure: a meta-analysis of randomized trials. Implications for public health. Journal of Human Hypertension. 2002; 16, 761-770
10. He FJ, MacGregor GA.  How far should salt intake be reduced? Hypertension.2003; 42, 1093-1099
11. NICE. Prevention of Cardiovascular Disease. Public health guidance 25. Published June 2010
12. Perry IJ, Beevers DG. Salt intake and stroke: a possible direct effect. Journal of Human Hypertension. 1992; 6, 23-25
13. Xie JX, Sasaki S, Joossens JV, et al: The relationship between urinary cations obtained from the INTERSALT study and cerebrovascular mortality. Journal of Human Hypertension. 6:17-21, 1992.

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