Obesity or being over-weight
After age 25, a person starts gaining weight, unless he does something about the food he eats and the amount of daily activity.
The reason is that, beginning at this age, the body starts to need less food because the metabolism is slowing down.
The result is that he requires about 10 less calories everyday for each year that passes, and if he does not cut back by this amount, he will end up gaining about ½ a kilogram a year.
In general, disease and death from heart disease are higher in direct relation to the degree of over-weight. Furthermore, from data obtained in the Framingham study, it appears that obesity may accelerate atherosclerosis and its effect is more apparent before age 50.
However, obesity is a disorder closely associated with other potent risk factors, i.e. hyperlipidaemia, hyperglycemia and hypertension.
The relationship between obesity and atherosclerosis is thus multifaceted, and since, in practice, obesity does not occur ‘independently’, it is of considerable importance as a risk factor.
Diabetes may be defined as high level of glucose in the blood, so that some of it overflows into the urine. Usually it is due to deficiency of insulin.
It is a chronic disease and affects the utilization of carbohydrates, fats and proteins. Diabetes causes a lot of complications, an important one being the narrowing of the blood vessels called atherosclerosis.
This change occurs at an earlier age in diabetics and is more extensive. The cause for this accelerated atherosclerosis is not known, although it is suggested that alterations in the ratio of high-density (HDL) to low-density lipoproteins (LDL) in plasma may play a role.
The role of glucose in atherosclerosis is poorly understood. Hyperglycemia is known to affect aortic wall metabolism.
Coronary artery disease is common in diabetics. Silent myocardial infarction is known to occur in diabetics and should be suspected whenever symptoms of left ventricular failure appear suddenly.
Diabetic patients, as a rule, suffer more heart attacks than non-diabetics, other factors remaining the same. Also, heart attacks in diabetics occur at a younger age than they do in non-diabetics.
Women who have diabetes suffer heart attacks more often so much so that in such cases the usual high ratio of heart attacks between males and females is very much lessened.
Heart attacks are also common in those people who do not yet have diabetes but their glucose metabolism on laboratory testing is found to be faulty, so that they can be labeled as pre-diabetics.
In a study abroad, it was found that 46 per cent of apparently non-diabetic patients with atherosclerotic coronary heart disease had an abnormal glucose tolerance.
In Kanpur, 49 per cent patients with coronary heart disease were found to have impaired glucose tolerance.
The way cigarettes bring on heart damage is still something of a mystery, but three possible explanations are:
Nicotine repeatedly over-stimulates the heart
The carbon monoxide absorbed into the blood takes the place of oxygen and hampers nourishment of the heart muscle and other tissues.
People with angina pectoris develop the chest pain quicker if they smoke. Even being in the same room with people who are smoking may aggravate these chest pains.
The smoke damages the lining of the coronary arteries, allowing artery-clogging cholesterol to build up and narrow the passage ways.
Evidence that heart attacks are common among smokers is now beyond serious dispute. The risk is in proportion to the amount of tobacco smoked. This includes the age at which smoking is begun, the number of cigarettes smoked and the degree of inhalation.
The risk of heart attacks occurring at an age below 40 years and of consequent sudden death is also more among heavy smokers than among non-smokers.
Discontinuance of smoking lessens this risk, so much so that those who smoked previously but stopped later on, five years later their chances of getting heart attack had come down to the same level as those of non-smokers.
The occurrence of heart attacks in several members of a family is a common observation.
It has been found that the incidence of heart attacks is nearly four times as frequent among siblings of persons (having common ancestors) with coronary disease as among siblings of persons without it.
High blood pressure (hypertension), cerebral haemorrhage or thrombosis and diabetes appear to occur with more than average frequency in some families.
Genetic factors seem to be involved in predisposing some families to these diseases. However, the role of common environmental factors cannot be minimised.
For example, in some families there are many members who are obese; while in some such cases, genetic factors may be involved, the role of the common habit of excessive eating among all the members, certainly contributes to this obesity.
An increased incidence of coronary disease has been related to lack of physical exercise and a sedentary occupation.
The societies in which economic privilege and physical inactivity go hand in hand, coronary heart disease tends to be more frequent among sedentary persons. They are also the people who tend to be obese and to eat more.
Post-mortem studies reveal that less atherosclerosis is found among those accustomed to physical exercise. These findings have been substantiated by experimental studies in animals as well.
Curiously enough, in India, coronary heart disease and consequent heart attacks have been found in almost equal frequency among manual workers as among those who are in sedentary occupations.
From this it may be inferred that in a disease with multiple factor etiology, the influence of one factor can be offset by a combination of other factors.