August 2014

Elevated Blood Cholesterol

The Role of Elevated Blood Cholesterol and
Lipids in Heart Disease and Stroke

 

Introduction

Years of observation and scientific research have demonstrated that there is a clear relationship between elevated total cholesterol, LDL-Cholesterol and blood lipid levels and heart disease. This is specifically important in Coronary Artery Disease (CAD), ischemic heart disease (angina), heart attack, congestive heart failure and arrhythmia (irregular heart rhythm).

CAD also sometimes called Coronary Heart Disease or CHD, is the most common cause of heart attack and heart failure and the leading cause of death in the U.S. Elevated blood cholesterol is one of the most important risk factors for coronary heart disease (CHD). CHD accounts for more than 490,000 deaths each year. Angina and nonfatal myocardial infarction (MI) are a major source of health problems in our country. It has been estimated that CHD will add more than $60 billion to health care costs in 1995 in medical expenses and lost productivity.

 

Who Is Affected?

Generally, the incidence of CHD is low in men and women under age 35 years of age. However, it begins to climbs rapidly during middle age for both men and women. Statistically the onset of CHD is delayed more than 10 years in women when compared with men. This is probably due to effects of estrogen in women, however, this is a misleading figure as women account for more than 49% of all CHD deaths in the U.S. in any given year.

 

Evaluating and Screening for CHD Risk

The present recommendation finding early CHD suggests periodic screening for elevated blood cholesterol in all men ages 35-65 and women age 45-65. According to the U.S. Government there is insufficient evidence to recommend for or against routine screening of asymptomatic persons over age 65, but recommendations to screen healthy men and women ages 65-75 may be made on other grounds such as history of high blood pressure, diabetes family history, smoking, lack of exercise and poor diet. The major problem in men and women over 65 is that blood cholesterol levels have proven to be inefficient testing procedure in determining risk of acute myocardial infarct or sudden death from heart attack.

The Government also believes that there is also insufficient evidence to recommend for or against routine screening in children, adolescents, or young adults without some extenuating circumstances such as family history of very high cholesterol, premature CHD in very close family members (father, mother, brothers and in some cases, grandparents). The Government does however, suggest that all people should receive periodic screening and counseling to reduce their risk of coronary disease because of smoking, poor diet, elevated blood pressure and limited physical activity.

It is also clear that CHD is a multifactorial problem that begins years before the onset of any symptoms or abnormal testing.

Autopsy studies in adolescents and young adults have in many cases, detected significant early lesions of atherosclerosis. This means that hardening of the arteries does not start in the adult years but rather during childhood. In line with the current philosophy of most medical doctors tend to wait until the child is at least 10 years of age or older or there is significant elevation of total Cholesterol, LDL-Cholesterol or significant increase in the Total Cholesterol/HDL-Cholesterol Ratio. Clearly this may be too late for many people especially since present Hypolipidemic therapy is basically aimed at slowing atherosclerosis down rather than completely reversing it.

The onset of atherosclerosis and symptomatic CHD may be much earlier in persons with inherited lipid disorders such as familial hypercholesterolemia (FH) and familial combined hyperlipidemia (FCH) therefore periodic screening from age 10 on every five years may be of value in identifying high risk individuals. This along with diet, exercise and new natural preventive and reversal programs can save tens of thousands of lives each year.

Many studies have demonstrated that there is a definite causal relationship between total Cholesterol, elevated LDL-Cholesterol and decreased HDL-Cholesterol levels and CHD. The majority of these studies show that risk increases in a continuous and almost linear curve. CHD risk begins with cholesterol levels as low as 150-180 mg/dL starting as early as 20 years of age.

During the middle years for each increase of 1% in total cholesterol, CHD risk increases by 3%. Cholesterol over 199 mg/dL is considered elevated (See U.S. Government Guidelines Regarding Heart Attack for a breakdown on cholesterol levels and risks). In the end however, since CHD is a multifactorial problem there is no clear relationship between blood levels of cholesterol and who will or will not develop CHD.

 

Generally studies however suggest the following:

  • Among middle age men 9%-12% of those men with cholesterol 240 mg/dL or greater will develop symptomatic
       CHD over the next 7-9 years. The problem is, however, in those men that do develop CHD, the majority also
       had one or more other risk factors that predispose them to developing CHD.
  • Mortality is greatest in men over the age of 45 and specifically in those men who smoked or had elevated blood
       pressure along with elevated total cholesterol.
  • Highest mortality occurred in men who had total cholesterols greater than 300 mg/dL.
  • Women generally had about one-half the CHD risk as men for the same cholesterol levels.
  • In both groups, men and women, CHD risk correlated greatly with level of elevation of LDL-Cholesterol and
       reduction of HDL-Cholesterol.
  • HDL-Cholesterol is generally a better predictor of CHD. When elevated there is a lower risk of CHD, when low
       there is a higher risk of CHD.
  •  

    Triglycerides and CHD Risk

    The relationship between elevated triglycerides and CHD is still for the most part unclear. There is evidence in three major studies that levels of triglyceride greater than 200-300 mg/dL was associated with greater risk of death from CHD in women. When adjusted for obesity, fasting blood sugar and low HDL-Cholesterol levels the data was less clear. In women age from menopause, use of estrogens, high blood pressure and diabetes presents a much higher risk of CHD and subsequent death from CHD. In men the issue appears to be much less clear.

     

    Value of Cholesterol Evaluations

    Cholesterol testing is most reliable when taken in a fasting state. Many factors can affect cholesterol levels including stress, minor illness, and seasonal fluctuations can cause serum cholesterol to vary between 4-11% within a specific individual. Laboratory error can compound this variation. The training and type of testing equipment and the testing procedure can create variations up to 14%.

    In recent years there has been a trend to look at cholesterol range rather than a single fixed value. For example an individual with a "true" cholesterol reading of 200 mg/dL can demonstrate test values in a range between 172-228 mg/dL. Looking at the low figure one would depreciate the individual's risk, looking at the high value one might believe that the individual was at greater risk than they actually are.

     

    Affect of Changing Diet on Lowering Cholesterol Levels

    The increase in cholesterol screening by private medical doctors has been associated with significant improvements in dietary knowledge, reduced fat consumption, and some decrease in CHD mortality. However, it is not entirely clear which screening factors (stop smoking, early treatment of elevated blood pressure, dietary education, or actual change in diet have lowered the risk of death from CHD. Studies have suggested that dietary advice alone has been responsible for only slight reduction in average cholesterol levels (1-3%) when compared to controls.

    Today cholesterol screening most important values is in educating the individual to CHD risk and in determining the need for prescription of hypolipidemic drugs.

     

    Use of Cholesterol Lowering Drugs

    Studies have suggested that the use of hypolipidemic medications, that is, drugs that lower cholesterol and/or triglycerides often slow down progression of atherosclerosis and by this means reduce the incidence and deaths from CHD. One particular drug, simvastatin (Zocor) when used in a group of men and women with active angina and prior myocardial infarct over a period of 5.4 years reduced CHD deaths by 42% and deaths from all causes by 30%.

    The benefits of using similar medications in asymptomatic persons to lower cholesterol are essentially undetermined. This occurs for two reasons. One, the risk of death from MI in otherwise asymptomatic persons is 20 to 30 times less then in already symptomatic groups. Second, most of the time the value of such treatment is not much greater than diet alone but when combined with diet may be of greater value. The problem here is that it is often difficult to get individuals who are asymptomatic, who have never had a heart attack to stay on a diet for prolonged periods of time in large groups.

    In a study of another hypolipidemic drug clofibrate (Lopid) when given to men 30-59 years of age for a period of 5-7 years lowered total cholesterol 9-10% and LDL-Cholesterol by 10-13%. In this same study the risk of death in this group decreased by some 25%. At first this sound very promising, however, this benefit was offset by the fact that in the same group there was a significant increase in non-cardiac deaths of 40% and increased a total death rate of 30%. This meant that people died four times more often from non-cardiac causes and increased death rate from all causes of 30%. This is by all means not a good situation, more is lost than gained.

    When other medications are looked at, modest reductions in MI and deaths from CHD are discussed, but in the end none are statistically significant in any of these studies.