Chapter 14

Patterns in Health and Disease:Epidemiology and Physiology

EXERCISE PHYSIOLOGYTheory and Application to Fitness and Performance,

6th editionScott K. Powers & Edward T. Howley

Epidemiology

• The study of the distribution and determinants of health states and the use of this information in the control of disease

• Uses of epidemiology:– Establish the cause of disease– Trace the natural history of disease– Describe the health status of populations– Evaluate an intervention

• Epidemiologic triad– Shows connections between the environment, agent,

and host that cause disease

The Epidemiologic Triad

Figure 14.1

Disease Control

• Destroying or removing the agent at its source• Altering the environment to reduce

transmission of the agent• Improving the host’s resistance to the agent• Altering the host’s behaviors

– Improved nutrition– Immunization– Exercise

Web of Causation• Difficult to establish the cause of chronic diseases

– Cardiovascular disease• Complex involvement of factors

– Risk factors– Genetic

• Heredity– Environmental

• Stress– Behavioral

• Diet• Smoking• Physical activity

Web of Causation

Figure 14.2

Major Risk Factor Categories

Figure 14.3

Leading and Actual Causes of Death

• Leading causes of death– Heart disease– Cancer– Stroke– Chronic lung

disease– Unintentional injuries– Diabetes

• Actual causes of death– Tobacco– Diet and physical

inactivity– Alcohol consumption– Infection– Toxic agents– Motor vehicles– Firearms

Coronary Heart Disease (CHD)

• Associated with atherosclerosis– Thickening of the inner lining of arteries– Contributor to heart attack and stroke death

• Diseases of the heart and blood vessels are the leading cause of death in the U.S.

• Associated with risk factors– Each risk factor magnifies the risk of CHD– Eliminating a risk factor causes a

disproportionate reduction in risk

CHD Risk Factors

• Primary– Increases risk of CHD in and of itself

• Secondary– Increases risk of CHD if primary risk factor is

present• Can’t be changed• Can be changed

Risk Factors for CHD

• Can’t be changed– Heredity– Gender– Age– Race

• Can be changed– Cigarette smoking– High serum

cholesterol– High blood pressure– Physical inactivity– Diabetes– Obesity– Stress

Determining Association Between Risk Factor and Disease

• Temporal Association• Plausibility• Consistency• Strength of association (relative risk)• Dose-response relationship• Reversibility• Study design• Judging the evidence

Physical Inactivity as a Risk Factor

• Independent risk factor for CHD• Relative risk of CHD is similar to other risk

factors– Smoking – High cholesterol – High blood pressure

• High population attributable risk– Percentage of population at risk– Due to large number of inactive individuals

U.S. Population at Risk

Figure 14.4

Metabolic Syndrome• Potential causative connections between risk factors

– Hypertension– Obesity– Insulin resistance– Dyslipidemia

• Leads to additional conditions– Hyperinsulinemia– Increased SNS activity– Increased blood volume– Increased resistance to blood flow

Metabolic Syndrome

Figure 14.5

Risk Factors for Metabolic Syndrome

• Abdominal obesity– Waist circumference >102 cm (men) and >88 cm

(women)• Hypertriglyceridemia

– ≥150 mg/dl• Low HDL cholesterol

– <40 mg/dl (men) and <50 mg/dl (women)• High blood pressure

– ≥130/85 mmHg• High fasting blood glucose

– ≥110 mg/dl

Obesity

• Prevalence in US adults– 65% are overweight (BMI = 25.0–29.9 kg/m2)– 30% are obese (BMI = ≥30.0 kg/m2)

• Linked to risk of CHD and metabolic syndrome

• Healthy People 2010 objectives for control of overweight and obesity– Nutrition objectives– Physical activity objectives