Modifiable risk factors cont.
High blood pressure
High blood pressure is a recognised risk factor for stroke, coronary heart disease, chronic kidney disease and heart failure. Cardiovascular risk increases in line with increasing blood pressure. More than 25% of adults in the UK have high blood pressure and up to 50% of them are not receiving treatment.1 Trials show that antihypertensive therapy is effective at reducing this risk.
The standard clinical definition of hypertension is a "sustained or repeated systolic blood pressure above or equal to 140mmHg or a diastolic blood pressure above or equal to 90mmgHg or both".
The risk of hypertension shows ethnic variation with patients of Afro-Caribbean origin being at higher risk than Caucasian patients.7
As hypertension is asymptomatic it is typically detected during opportunistic screening. Hypertension usually only becomes symptomatic when blood pressure reaches very high pressure levels usually exceeding 200mmHg systolic. Symptoms of high blood pressure can include nose bleeds, headaches and dizziness.
A 12/6mmHg reduction in blood pressure has been shown to reduce the risk of stroke by 40% and coronary heart disease by 20%.4 Patients can be advised that each 2mmHg reduction in systolic blood pressure can reduce the increased risk of CHD by 7% and the increased risk of death by stroke by 10%.8
As a consequence high blood pressure is one of the most important preventable causes of cardiovascular conditions and the associated morbidity and mortality.
Blood cholesterol levels
Cholesterol and triglycerides are both derived from dietary fat. More than 50% of adults in the UK have high cholesterol levels (5mmol/l or above).1
Total blood cholesterol is made up of low density lipoprotein (LDL-C) and high density lipoprotein (HDL-C) cholesterol.
HDL-C is commonly referred to as "good cholesterol" as it transports cholesterol from the peripheral tissues to the liver for excretion as biliary cholesterol or bile salts. HDL-C is considered to have a cardio protective effect and higher levels are beneficial.
LDL-C is referred to as "bad cholesterol" as this form of cholesterol is primarily responsible for the development of atherosclerosis. LDL-C reduction is a primary target for cholesterol lowering strategies.
The ratio between total cholesterol and HDL-C is closely related to cardio-vascular risk. The greater the level of total cholesterol in relation to HDL-C the higher the risk of cardiovascular events. Ratios of less than 4 are considered ideal whilst those over 6 would be concerning.9
The ratio of total cholesterol-to-HDL is important; the lower the number the better. For example, a patient with a total cholesterol level of 5mmol/l and an HDL of 2 would have a ratio of 2.5 (5÷2= 2.5). If that person's HDL was lower, for example 0.5mmol/l, the ratio would be increased to 10 (5÷0.5 =10), and the patient would be at higher risk of CVD.
A systematic review of 58 RCTs has shown that a 1mmol/l reduction of LDL-C reduces the risk of fatal cardiovascular events and non-fatal myocardial infarction by:
- 11% in year one
- 24% in year two
- 33% in years 3-5
- 36% in subsequent years10
Increased blood levels of triglycerides are also associated with increased cardiovascular risk. Levels of triglycerides in fasting blood samples above 1.7mmol/l have been shown to increase the risk of CVD. Triglyceride levels have been shown to correlate closely with the risk of cardiovascular disease.
Unhealthy diet
Diet is a significant risk factor for cardiovascular disease. Diets high in saturated fat will raise LDL cholesterol levels increasing the risk of atheroma development and arterial occlusion. Diets high in fat also provide more calories per gram than other nutrients and will contribute to weight gain.
Diets high in salt are likely to result in high blood pressure or kidney disease both of which are independent risk factors for cardiovascular disease.