Introduction To Epidemiology and Physical Activity

Introduction To Epidemiology and Physical Activity “Epidemiology is the study (or the science of the study) of the patterns, causes, and effects of health and disease conditions in defined populations. It is the cornerstone of public health, and informs policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive medicine. Epidemiologists help with study design, collection and statistical analysis of data, and interpretation and dissemination of results (including peer review and occasional systematic review). Epidemiology has helped develop methodology used in clinical research, public health studies and, to a lesser extent, basic research in the biological sciences.” (source)

Introduction To Epidemiology and Physical Activity The main goals of population medicine are the control and primary prevention of disease within a large group of people. People who are at risk for developing a disease are identified, and measures are then taken to reduce those odds (risk) by identifying and altering (risk) factors that cause disease. The role of physical activity in promoting the longevity and health of the public has become increasingly important for most developed, and many developing, nations.

Introduction To Epidemiology and Physical Activity In addition to the cost of human suffering resulting from poor health, the financial burden of poor health is great, as illustrated in figure 0.1 (next slide). Percentage of gross domestic product has increased steadily during the past 50 years, from about 4% in the 1940s to a projection of 18% in 2010. This means that 18 cents of every dollar spent in the United States is spent on some aspect of health care.

Introduction To Epidemiology and Physical Activity Figure 0.1 - The trend in U.S. health costs, expressed in billions of dollars and as a percentage of gross domestic product (GDP). Data from Centers for Medicare and Medicaid Services, Office of Actuary National Health Expenditures, 2009.

Introduction To Epidemiology and Physical Activity The cost for each person in the United States was about $8,000 in 2007 and is approaching $9,000 a year, which is higher than in other leading economies worldwide including Canada, France, Germany, Japan, and the United Kingdom, which all have longer life expectancies (figure 0.2, next slide). The rate of increase in health expenditures in the United States is expected to be 6.2% each year through 2018. The distribution of U.S. health care costs is illustrated in (figure 0.3, sequential slide)

Introduction To Epidemiology and Physical Activity Figure 0.2 - Health care expenditures and life expectancy in the United States and other nations. Data from OECD Health Data 2009. Available: http://www.oecd.org/health/healthdat

Introduction To Epidemiology and Physical Activity Figure 0.3 - Where the U.S. health dollar was spent, 2007.

Introduction To Epidemiology and Physical Activity Coronary heart disease (CHD) alone accounts for 20% of deaths in the United States each year. Other diseases and conditions that are common, deadly, and costly in the United States and that can be helped by physical activity are listed in table 0.1. (next slide)

Introduction To Epidemiology and Physical Activity The statistics in the table above illustrate the three main ways by which the health impact of diseases, and the health-promoting potential of physical activity, are traditionally judged in the field of epidemiology. Hence, the number of people affected, odds of death, and overall financial burden make a strong case that the highest priority for public health is determining whether and to what extent physical activity protects against CHD.

Introduction To Epidemiology and Physical Activity The association between physical activity and health is sufficiently strong to justify the inclusion of physical activity and fitness as key indicators of health promotion in the United States. Figure 0.4 (see pg. xviii, text) shows how many deaths from leading diseases in the United States might be attributable to exposure to 12 risk factors. (Estimates for 2005) Of the 2.5 million U.S. deaths in 2005, nearly half a million were associated with tobacco smoking, and about 400,000 were associated with high blood pressure; each accounted for about 1 in 5 deaths in U.S. adults. Physical inactivity accounted for nearly 1 in 12 deaths.

Introduction To Epidemiology and Physical Activity A summary of 10 studies from six countries (three from the United States; two each from Canada and the Netherlands; and one each from Australia, Switzerland, and the United Kingdom), using population estimates of physical inactivity with relative risks of inactivity for specific diseases, estimated that The annual excess cost in 2003 U.S. dollars (direct, indirect, or both) per inactive person per year ranged from $109 to $1305 (median $172) - estimated annual direct medical costs of physical inactivity per inactive person for five U.S. states (Georgia, Minnesota, New York, South Carolina, and Washington) ranged from a low of $20 in Washington to $80 in Georgia. The yearly cost directly attributable to inactivity in the United States is an estimated $23 to $76 billion, or 1.5% to 5.0% of national health care expenditures.

Introduction To Epidemiology and Physical Activity The main goals of population medicine are the control and primary prevention of disease within a large group of people. Disease is medically defined as reduced, abnormal, or lost structure or function of cells, organs, or systems of the body. The main adverse effects of disease include impairment of bodily functions, disfigurement, and death. Conversely, health is not simply defined as the opposite of disease. In 1946, the World Health Organization (WHO) defined health as a “state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity” (WHO 1946)

Introduction To Epidemiology and Physical Activity Hence, health is relative rather than absolute. Lost function results from illness, but it can also occur in the absence of disease. For example, lost strength and mobility can result from wasting of muscle and reduced joint flexibility after insufficient use regardless of whether or not someone is free of disease. Though longevity has been a longstanding benchmark in the field of epidemiology, WHO recently adopted the concept of healthy life expectancy as a better index of health around the world (figure 0.5, next slide ). This concept is based on disability adjusted life expectancy, which subtracts years according to the prevalence and severity of diseases that impair human functioning and quality of living.

Introduction To Epidemiology and Physical Activity Based on analysis of 1990 disease and injury rates worldwide by the United Nations Global Program on Evidence for Health Policy, the United States ranked 24th of 191 countries, with a per capita healthy life expectancy of 70 years, compared with the highest-ranked countries, Japan, Australia, France, Sweden, Spain, and Italy, which had healthy life expectancies ranging from 73 years to around 74.5 years. By 2007, the United States ranked 38th. Men and women in the United States can now expect to live their last eight to nine years with some type of disability – causes of disability – next slide Figure 0.5 - Healthy life expectancy for U.S. men and women.

Introduction To Epidemiology and Physical Activity The World Health Organization has defined healthy life expectancy as disability-adjusted life expectancy; the United States ranks 38th worldwide, with a per capita healthy life expectancy of 78 .2 years

Introduction To Epidemiology and Physical Activity Loss of function, which contributes to disability, increases with increasing age but usually geometrically; the loss is proportionally greatest in the later years rather than in the middle years of life. The ultimate goals of community medicine and epidemiology are to find and implement ways to lessen the slope of the decline of the aging curve (figure 0.6, next slide), to square off the rapidly accelerating loss in the later years of life, and add a few healthy years. Thus the goals are for people to get sick later, lose function more slowly, live longer, and then die quickly when it’s time

Introduction To Epidemiology and Physical Activity Figure 0.6 - Physical functioning across age for active compared to sedentary people.

Introduction To Epidemiology and Physical Activity Research confirms that both men and women who are physically active and have normal body mass index (a measure of fatness) maintain higher cardiorespiratory fitness throughout adulthood when compared with people who are inactive and obese Other evidence supports that people with low physical activity are twice as likely to die early and 50% less likely to report excellent health prior to death compared to people who stay physica.ly active as they age Thus, this course and text book presents the theory and the evidence that a habit of physical activity contributes in a meaningful way to both quantity and quality of life. It also teaches you how to think like an epidemiologist and critically evaluate cause and effect from research studies conducted in the field of epidemiology.

Introduction To Epidemiology and Physical Activity See also – Facts about Physical Activity in the United States (Centers for Disease Control and Prevention) End of Lecture