Title: Vascular Disease In Advancing Age.
Key words: Cardiovascular disease, ageing, risk factors, hypertension, diet.
Date: Aug 1999
Category: 13. Specific conditions
Author: Dr Van Rhijn
Vascular Disease In Advancing Age.
Cardiovascular disease (CVD) and stroke rates continue to be the principal cause of mortality1, serious illness and long-term disability in the western world2, compared to elderly populations in the underdeveloped areas. Although long-term dietary differences are partly responsible for this discrepancy, the disease is secondary to a gradual, cumulative effect3 over decades from numerous contributing factors, which will be further discussed.
The principal risk factors include family history, male gender, short stature, smoking4, hypertension5, and hypercholesterolaemia6. Other established risk factors include diabetes, obesity, physical inactivity, thrombogenesis, factors associated with foetal7 & infant growth and nutrition (salt, fat, refined carbohydrate, fruit and vegetables).
The pathological lesion underlying CVD is atherosclerosis. The endothelial dysfunction may be due to a combination of risk factors, leading to free radical damage and inflammatory processes8. Elevated plasma homocysteine levels are a risk factor for CVD9,10, especially atherosclerosis11, thrombosis and carotid-artery stenosis12. Homocysteinuria, commonly prevalent in elderly, may be due to an autosomal recessive deficiency of cystathione b -synthase, or secondary to deficiencies in vitamin B-613, B-1214 and folate15, 16, required for its metabolism. Homocysteinaemia may be responsible for increased proliferation of vascular smooth muscle cells, and perhaps interfere with endothelial cell function as well17.
Hypercholesterolaemia, in particular low-density lipoprotein (LDL) cholesterol18, is a principle risk factor for atherosclerosis, and cholesterol reduction is associated with a reduction in risk.
Low fat diets19 and diets rich in mono- and polyunsaturated fatty acids are effective in decreasing LDL-cholesterol concentrations20. High-density lipoproteins are protective against CHD21.
There is increasing evidence that free radical damage22 contributes to the aetiology of CVD. Antioxidant supplementation (Vit C) has beneficial effects on risk factors (hypertension)23, 24, 25. Epidemiological studies suggest a protective, antioxidant effect of vitamin E in CVD26, 27, by increasing the resistance of LDL oxidation28 and inhibiting proliferation of vascular smooth muscle cells29.
Although hypertension is regulated by a myriad of mechanisms, the consumption and handling of salt by the kidney are critical factors. The current salt intake in the western diet has increased 10 fold (150 200 mmol/day), causing an increase of extracellular volume of 1 2 L30, which contributes to hypertension with advancing age31. Dietary salt restriction has a significant hypotensive effect32, 33 and subsequently reduces risk of vascular disease such as strokes, coronary heart disease and all causes of mortality34.
Chronic diabetes may lead to microvascular (increased capillary permeability - haemorrhages35) and macrovascular disease (thrombogenesis) due to poor conversion of n-3 and n-6 essential fatty acids to their longer-chain metabolites via the insulin-dependent desaturation step36.