Biomarkers and Assessment of Health

Biomarkers and Assessment of Health Status

Biomarkers refer to the key physiological factors associated with aging. Biointerventions are actions that are designed to retard or reverse the aging process. Biomarker of functional age estimate the rate at which the very fundamental processes of aging occur within individuals. Biomarkers include:

  • Lean body mass as measured by the Body Mass Index (BMI);
  • Strength;
  • Basal metabolic rate (BMR);
  • Body fat percentage.

These four biomarkers are closely interrelated and are viewed as the primary catalysts for preventing sarcopenia (an age-related loss of muscle).

Lean Body Mass

It is a well-established fact that many Americans have too much body fat and too little muscle. Body fat is metabolically inactive – it is energy storage tissue. Everything that is not body fat (e.g., bones, vital organ tissue, and central nervous system) is referred to as lean body mass – the body’s biologically active tissues. Muscle is responsible for the vitality of the whole physiological apparatus. Lean body mass is measured by using the Body Mass Index, which tells us how much of our weight is muscle and how much of our weight is fat. The key to senior rejuvenation is building muscle. Studies show that a high ratio of muscle to body fat on the body offers the following benefits:

  • Increases in metabolism to help burn body fat and alter body composition
  • Increases in aerobic capacity – the health of one’s cardiovascular system – because more working muscles consume oxygen
  • Muscle use of more insulin, greatly reducing the chances of developing diabetes
  • Higher maintained levels of the beneficial HDL cholesterol in the blood

Keeping track of muscle loss is essential in seniors. Not only is it one key to decreased vitality, it is increasingly used by insurance companies as an indicator of overall health. Many studies have shown that as Americans move from young adulthood into middle age, they tend to lose about 6.6 pounds of lean body mass each decade of life. After age 45, the rate of loss accelerates. Studies have also shown that mortality is affected by lack of lean body mass.

Strength

Two factors are responsible for how much muscle people have. The first involves how often muscles are used while the second centers on the level of tissue-maintaining anabolic hormones circulating in the blood. How frequently muscles are used partly determines their size and lifting capacity. A muscle that is frequently used is also pushed to the limits of its capacity will grown and gain strength (even in seniors). Regardless of seniors’ ages or levels of weakness, they can regain muscle mass and strength.

Isometric exercises, which involve using force applied to resistant objects, build muscle mass. An example of this type of exercise is pushing against a wall with your arms. Tension builds up in your muscles, although your arms do not move.

Basal Metabolic Rate

Metabolism refers to the body’s chemical processes that build and destroy tissue and release energy, thereby generating heat. Basal refers to the rate of the body’s metabolic processes at baseline, or at rest. The basal metabolic rate is the rate of your body chemistry exertion is minimal. The BMR, or calorie expenditure at rest, decreases with age. As noted earlier, reduced muscle mass is primarily responsible for this gradual reduction. Based on estimates of the average loss of lean-body mass with age, a person’s BMR drops about 2 percent per decade. To correlate this with caloric need, with each decade from age 20 onward, people need about 100 fewer calories per day to maintain their body’s status quo.

Body Fat

With advancing age, most people gain fat even if their body weight hasn’t increased much. The body’s ratio of lean body mass to fat decreases with age. Despite this, losing weight should not be the goal. More appropriately, the goal should focus on shedding fat and gaining muscle. The combination of exercise and moderate caloric restriction is the best method yet devised to lose weight and unwanted body fat in a healthful manner.

Other Biomarkers

Aerobic Capacity

Aerobic capacity is the body’s ability to process oxygen within a given time. The process of oxygenation includes the body’s ability to perform the following tasks:

  • Rapidly breathe amounts of air into the lungs to oxygenate blood
  • Forcefully deliver larger volumes of blood via the pumping action of the heart
  • Effectively transport oxygen to all parts of the body through the blood stream

By age 65, aerobic capacity is typically 30 to 40 percent smaller than in young adults. However, studies indicate that the decline is less in seniors who exercise regularly.

The V02 max (or maximum oxygen consumption) represents the ability of the heart and cardiovascular system to respond to stress. V02 max shows how much air the lungs can ventilate. It declines with age and poor physical fitness, reflecting a lower maximal attainable heart rate plus a lower capacity of the tissues to extract oxygen quickly from the blood. To achieve V02 max levels equivalent to those of young adults, seniors must exercise regularly over a longer period of time.

The amount of air that can be taken in and breathed out rapidly in one very deep breath is the measurement of lung function called forced vital capacity (VC). It reflects the integrity of the whole respiratory system: the chest muscles and diaphragm, the central nervous system control mechanisms, and the elasticity of the lungs. VC declines about 40 percent between youth and 70 years of age.

Blood Pressure

When taking blood pressure, the upper number, or systolic pressure, is the pressure blood exerts on the arterial walls during the heartbeat. The lower number, or diastolic pressure, is the pressure remaining in the arteries between heartbeats. In adults, a blood pressure of 140 systolic and/or 90 diastolic is commonly considered to be at the upper limit of normal blood pressure.

Hypertension refers to abnormally high blood pressure. Although there are usually no notable symptoms in the early stages of hypertension, this certainly does not mean that high blood pressure is not dangerous. It is highly associated with strokes and heart attacks, among other serious problems. The myriad causes of elevated blood pressure include heredity, obesity, high fat intake, excessive salt intake, alcohol, smoking, and too little exercise. Fortunately, most of these lifestyle choices are controllable. Hypertension is serious enough to require medical evaluation, but it can be effectively managed through diet and prescription medications.

Blood Sugar Tolerance

The ability of the body to control blood sugar (glucose) is called glucose tolerance. With advancing age, the body gradually loses the ability to take up and productively use sugar from the bloodstream. By age 70, approximately 20 percent of men and 30 percent of women have an abnormal glucose tolerance curve, which increase the risk of developing diabetes. Fortunately, researchers are discovering that this age-related decline is more closely associated with seniors’ higher body fat content and lower muscle mass than with the pancreas’s diminished ability to secrete insulin.

Dietary sources of glucose are starches (bread, pasta, potatoes) and foods that taste sweet. The process of digestion breaks down carbohydrate starches into individual sugar molecules that enter the bloodstream as glucose – no matter how much starch is consumed; the body tries to maintain blood glucose at relatively constant levels. The more direct causes of insulin insensitivity are two factors associated with aging: increased body fat and inactivity. A third cause is a diet rich in fat.

Fortunately, the combination of a high-fiber diet and exercise can often transform a previously insufficient amount of insulin from the pancreas to an adequate amount. Exercise increases the insulin sensitivity of the tissues and improves carbohydrate metabolism.

Cholesterol/HDL Ratio

Cholesterol, a fatty substance, is a necessary component of the body. Bound to proteins, cholesterol circulates in the bloodstream as lipoproteins. Under certain circumstances, cholesterol can collect to form deposits in tissues or create blockages within the arteries of the heart. Blockages within blood vessels, referred to as atherosclerosis, contribute to the development of heart disease and other circulatory disorders. Blockage within the arteries of the heart can lead to a heart attack. Deposits built up within the arteries of the brain may cause a stroke.

While rates of death from heart disease have decreased in recent decades, it remains the leading killer of men and women in America. Cholesterol levels, family history, diet and exercise are all significant factors in heart disease. Research shows that the risk of heart disease is greater in those with a family history of the disease. The good news is that by following a low-fat diet, not smoking, and exercising regularly, the risk can be reduced. Although some high cholesterol foods, such as egg yolks, put cholesterol directly into our system, the liver manufactures most of the body’s cholesterol. Cholesterol is not required in the diet, as the body is capable of producing all it needs. But that process is greatly influenced by the amount of fat in the diet. Products labeled “no cholesterol” can still raise blood cholesterol levels if they are not also low in saturated fat.

Cholesterol is commonly divided into two categories: good cholesterol, known as HDL (high density lipoprotein), and bad cholesterol, known as LDL(low density lipoprotein). The key to managing blood cholesterol is to increase of the beneficial HDL and lowers the level of LDL. Adjusting one’s eating and nutritional habits also helps lower levels of bad cholesterol.

LDL contributes to the development of heart disease by causing waxy, obstructive plaque buildup within the coronary arteries. HDL does just the opposite. Among other things, HDL appears to act as a kind of scouring agent, total cholesterol count is not the primary issue. The cholesterol/HDL ratio is considered a better predictor of heart disease than the cholesterol level alone. This ratio equals the total cholesterol divided by the HDL. The ratio goal for middle-aged and older men and women should be 4.5 or lower. Harmful LDL can be lowered only by diet change. This, however, will not raise the level of HDL in the blood.

Factors that raise HDL levels include exercise and lowering body fat, as well as quitting smoking. Obesity, especially that found around the abdomen, is a great health risk. This type of obesity correlates with low HDL concentrations. Fat distributed about the abdomen is called above the belt obesity and is a serious risk factor for arteriosclerosis and adult-onset diabetes.

The term fiber refers to the portions of plants that mammals cannot digest and, therefore, cannot be absorbed through human intestines. Fibers are the substances present in cell walls that vie plants their structure and form. Generally speaking, water-soluble fiber helps lower blood cholesterol while insoluble fibers help normalize bowel function and prevent both bowel cancer and diverticulitis. According to studies, the average-size person should consume at least 40 grams of total fiber per day.

Bone Density

Osteoporosis is a disease that causes bones to thin and weaken. Osteoporosis is often called the “silent disease,” because it acts unnoticed until the first sign of the disease – often a broken bone. According to the National Osteoporosis Foundation, osteoporosis is a major public health threat for an estimated 44 million Americans (NOF, 2003). In the United States today, 10 million individuals are estimated to already have the disease and almost 34 million more are estimated to have low bone mass, placing them at increased risk for osteoporosis. Of the 10 million Americans estimated to have osteoporosis, 8 million are women and 2 million are men. Thirty-four million Americans, or 55 percent of the people 50 years of age and older, have low bone mass, which puts them at increased risk of developing osteoporosis and related fractures.

At greatest risk for developing osteoporosis are women who have a family history of the disease, have small body frames, and experienced early menopause. The high incidence of bone loss in women is thought to be associated with hormonal changes that occur during menopause. Lower levels of estrogen are believed to contribute to its development, which prompts many women to choose hormone replacement therapy. In addition to hormonal changes, other causes of bone loss and osteoporosis may include diets low in calcium and insufficient exercise.

The first symptoms of osteoporosis may be a reduction in height or bone breakage. Thanks to medical advances, physicians can accurately test for osteoporosis by using dual energy X-ray absorptiometry (DEXA). This measures bone density in the wrist, hip, and lower spine. Other tests include use of single photon absorptiometry, dual energy, absorptiometry, and quantitative computed tomography. Those who believe they are at risk for developing osteoporosis should talk with their physicians about obtaining bone density evaluations.

A lifelong diet high in calcium and vitamin D is critical for developing strong bones. A diet rich in magnesium is also important, as it aids in calcium absorption. Research shows that two weeks of complete bed rest can cause much calcium loss from bones as one whole year’s worth of aging. Today, the medical community agrees that repeated stress placed on a bone causes it to become stronger, rather than weaker. Numerous studies have shown that weight-bearing exercise, such as walking, running, tennis, and cycling, continued over an 8- to 24- month time span, can effectively reduce the rate of bone loss. As stated previously, always check with a physician before advising a senior client to being any exercise program.

Treatment of osteoporosis is commonly directed toward stopping further bone loss and preventing falls. Hormone replacement therapy is controversial but common therapy in post-menopausal women.

Body Temperature

Dehydration and heat-related injuries are common among seniors because of the body’s vital thermoregulatory abilities – including a lower metabolic rate and a decreased ability to shiver – diminish with age. As such, both hot and cold weather pose dangers to seniors.

A reduced sensation of thirst contributes to senior’s thermoregulatory problems. It is believed that, as a group, seniors do not drink enough water. Older exercisers also tend to have a lower heart rate response and a smaller heart stroke volume than younger people. This reduced cardiac output impairs blood flow to the skin, where heat build-up in the body would normally find its escape through sweat. This means that heat can remain trapped inside the body, allowing internal temperatures to soar to dangerous, even fatal, levels.

Shivering, the opposite of sweating, is the body’s way of generating heat (thermogenesis). Just as an inability to sweat leads to possibly dangerous high temperatures in the body, the inability to shiver can leave internal body temperatures dangerously low.

The information above is reprinted from Working with Seniors: Health, Financial and Social Issues with permission from Society of Certified Senior Advisors® . Copyright © 2009. All rights reserved. www.csa.us