While CVD death rates have fallen from their peak during the 1970s to1980s, CVD represents an increasing cause of disability or ill-health. Factors which increase the risk of developing CVD may be categorised as modifiable, such as smoking, high BP, high blood cholesterol, diabetes, obesity and sedentary lifestyle, and non-modifiable, such as family history of CVD, increasing age, and ethnicity. While males are more likely to develop CVD at a younger age, the lifetime CVD burden is greater in women because of their greater longevity and an increased risk of stroke over 75 years.
The epidemic of CVD witnessed in the UK during the past 50-60 years has been strongly linked with changes in lifestyle and dietary habits, and correction of these as discussed below, may have important benefits, both to individuals at risk of CVD (primary prevention) and those already with established CVD (secondary prevention).
Stopping smoking is probably the single most effective measure to reduce CVD risk in addition to its multiple other health benefits. Attending a formal intensive smoking cessation support service is strongly recommended and is associated with improved short and longer term cessation rates.
Obesity increases the risk of high BP and diabetes. Maintenance of an ideal body weight for height (BMI 20-25 kg/m2) is encouraged. The avoidance of central obesity - defined as a waist circumference of >40 inches (102cm) in men or >35 inches (88cm) in women - is particularly important as central obesity is associated with increased visceral fat deposition and has been identified as an independent predictor of CVD risk. In Asians, <90 cm in men and <80 cm in women is considered desirable. Waist measurements should be made with a tape measure placed around the bare abdomen, parallel to the floor and midway between the iliac crest and lower rib margin on each side. The subject should relax and exhale while the measurement is taken.
Regular aerobic physical exercise (30 minutes of at least moderate intensity exercise per day, most days of the week) is recommended. Regular exercise may help reduce obesity, reduce BP, and modestly improve lipids. Suitable exercise includes brisk walking, using stairs, commuting on foot or by bicycle, and active recreation or social sport. Those unable to undertake such exercise due to other medical conditions should aim to exercise regularly at their maximum safe capacity. If finding time for 30 minutes of exercise is impractical, it is worth noting that shorter bouts of physical activity of 10 minutes or more accumulated throughout the day may be just as effective as longer sessions of activity. Use of pedometers or membership of an exercise class may be beneficial for sustaining a lifestyle of regular exercise. Following a coronary event or need for revascularisation (stenting or bypass), formal referral to a cardiac rehabilitation class, which typically includes a strong emphasis on exercise where appropriate, may significantly improve long-term CVD outcomes.
Dietary intervention is of value in modifying several risk factors either alone or in conjunction with pharmacological therapy. Reducing overall energy (calorie) intake in a balanced fashion will clearly be necessary if obesity is present. In addition, UK guidelines, based on clinical trial evidence (largely epidemiological studies) or consensus opinion, have given advice on appropriate dietary modification for those with or at high risk of CVD. Such dietary advice could also reasonably be extended to the majority of the UK adult population.
A meta-analysis of randomised controlled trials of reducing saturated fat (using monounsaturated or polyunsaturated fats as replacement) with at least two years follow up showed a 24 per cent risk reduction for CVD events. It is recommended that dietary intake of total fat should be limited to ≤30 per cent of total energy intake. Intake of saturated fats should be ≤10 per cent of total energy intake (i.e. no more than one third of total fat intake) and saturated fats should be replaced with monounsaturated fats where possible.
Dietary cholesterol has relatively little effect on blood lipid values but there may be variation in response between individuals, and dietary cholesterol intake has been related to the development of CHD in some epidemiological studies. It is thus recommended the intake of dietary cholesterol is limited to ≤300mg per day.
Fruit and vegetable consumption, in a meta-analysis of epidemiological studies, is inversely related to risk of CHD. At least five portions of fresh fruit and vegetables per day are encouraged.
Epidemiological studies show regular fish consumers to be at lower risk of fatal CHD, including sudden death. At least two servings of oily fish per week are encouraged.
Alcohol consumption of 1-3 units per day (a unit equates to about 80 ml of wine, 250 ml of normal strength beer, and 30-50 ml of spirits) is associated with lower coronary mortality. Consumption above this increases systolic and diastolic BP, and the risk of cardiac arrhythmia, cardiomyopathy and sudden death. Alcohol intake should be limited to <21 units/week (<4units on any single day) for men and <14 units/week (<3units on any single day) for women.
Finally, a reduction of sodium intake, especially in the form of sodium chloride, will also reduce BP. Salt intake should be limited to <100 mmol/l per day (<6g of sodium chloride or <2.4 g of sodium per day).
Dr Menown is consultant cardiologist and director, Invasive Cardiology
Craigavon Cardiac Centre, Northern Ireland and President of the Irish Atherosclerosis Society
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