Download Course Learning Outcomes for Unit II Reading Assignment Unit

UNIT II STUDY GUIDE
Morbidity, Mortality, and
Descriptive Epidemiology
Course Learning Outcomes for Unit II
Upon completion of this unit, students should be able to:
1. Present key concepts regarding evaluation of the cause, prevention, and treatment of disease in
communities.
1.1 Explain the term “population at risk” and provide examples relevant to modern epidemiology.
1.2 Explain the meanings and uses of incidence, prevalence, morbidity, and mortality in
epidemiology.
4. Differentiate among descriptive, interventional, and observational studies in public health.
4.1 Describe the primary objectives of descriptive epidemiology, distinguishing it from analytic
epidemiology.
4.2 Distinguish between secular trends and cohort effects in epidemiology.
4.3 Differentiate among ratios, proportions, and rates as used in epidemiology.
Reading Assignment
Chapter 3:
Measures of Morbidity and Mortality Used in Epidemiology
Chapter 4:
Descriptive Epidemiology: Person, Place, Time
Unit Lesson
Causes of Mortality in the United States
It is very interesting to study historical patterns in causes of death, observing trends over time, and also
examining differences among various nations and cultures. We will save the international comparisons for
another lecture, but here we will discuss changes in U.S. causes of death over the past 110 years.
Studying trends in mortality can tell us about the progress of medicine over time, the progress of public health
measures, and it can also tell us where such progress has taken place most quickly and where we still lag
behind. In this lecture, we take a look at causes of death in 1900 and in 2010 (the most recent available data),
making comparisons and considering the implications for epidemiology and community health.
1900
At the turn of the last century, the chief causes of death in America were infectious diseases, things which we
generally do not expect to kill people today. The number one cause of death was, believe it or not,
pneumonia/influenza. The two were grouped together because it was difficult at that time to determine exactly
which disease the patient had. Today, patients who contract pneumonia or influenza are treated aggressively
with antibiotics, hydration, and advanced respiratory therapy, and most recover quickly. Many patients with
these conditions are not even admitted to the hospital today. Prior to the development of effective antibiotics
in the 1930s, pneumonia was a very serious condition, and a significant number of patients did not survive.
Influenza was also a major cause of death at that time, and it spread through entire communities, killing
thousands. The “flu shot” came along much later. The second leading cause of death was tuberculosis (TB).
In 1900, techniques of screening for tuberculosis were poorly developed, and antibiotics to treat the condition
did not yet exist. Truly, all that medical professionals could do with active TB cases was to isolate them from
the community in “sanatoriums” as they were called. Sanatoriums offered rest and nutrition, hoping to boost
PUH 5303, Concepts of Epidemiology
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the patient’s immune function and support his or her recovery from the disease. Some patients survived, and
the active infection eventually subsided, but many TB patients died. Remarkably, gastrointestinal (GI)
infections such as gastritis, enteritis, and colitis were next among the causes of death in 1900. Today, such
patients receive IV hydration, appropriate medications, electrolyte therapy, and very few people die of such
infections. There is simply no reason for anyone to die of a GI infection if they seek treatment soon enough.
Heart disease was on the list in 1900 at the fourth spot. However, as you will learn soon, it has become a
much more important cause of death today. The other chief causes of death in 1900 help us to reflect on the
limitations of medical knowledge at that time. A category called senility, ill-defined conditions, was the fifth
leading cause of death in 1900. Vascular lesions affecting the central nervous system (today we would say
stroke or cardiovascular accident) were sixth, and nephritis also made the list.
2010
The most currently available data for leading causes of death in America is for the year 2010. You will see
here that the focus has shifted from acute, infectious causes to chronic diseases as causes of mortality. Heart
disease is the number one cause of death today, replacing all of the infectious causes from the past. At least
part of its position at the top is related to the modern American diet, which contains far too much animal fat. In
the early 1900’s, Americans had very little access to red meat, consuming it only on special occasions; they
relied mostly on grains and vegetables which they could grow. When they consumed meat, it was likely
chicken or pork. Beef was very expensive in 1900, hard to obtain. It will not surprise the reader that cancer is
the second leading cause of death today. It did not even appear on the list in 1900, perhaps because it was
so poorly understood at the time. Most cancer deaths probably fell under “ill-defined conditions.” There are
many reasons for the high cancer rates in America today, and all the deaths, but none of them compare in
impact to cigarette smoking. Chronic lower respiratory diseases are third on the list for 2010, with emphysema
being primary among them. Poor urban air quality is partly to blame here, but cigarette smoking is
undoubtedly the leading factor in these deaths. Stroke is fourth on the list today, and accidents come in fifth,
with motor vehicle accidents in particular representing the largest share. In 1900 there were so few
automobiles on the roadways that motor vehicle crashes were infrequent. Alzheimer’s disease and diabetes
have also climbed onto the list for 2010. The increase in diabetes in America is simply alarming today, and
this is almost certainly related to obesity and dietary choices.
The mortality pattern which we see can be summarized in this way: Americans no longer die frequently from
infectious disease. We have, at least to some extent, improved community health measures and medical
treatment to help our citizens survive infections. Life expectancy for someone born in 1900 was only 48 years.
Therefore, many of the chronic diseases that kill Americans today never even had time to develop in persons
born in that era. With so many Americans dying of influenza, pneumonia, and tuberculosis at that time,
chronic disease was less of an issue. Today, life expectancy for Americans is nearly 80 years; we are living
long enough to develop a diversity of chronic illnesses that eventually take our lives.
The focus of epidemiology must shift. The next improvements in American health and longevity will not come
from better medications and more advanced technology. They will come from improved lifestyles, reducing
the impact of behaviors such as smoking, poor dietary choices, sedentary lifestyle, and unsafe driving
practices. The reality is this: the things which kill Americans today are related to personal choices and
lifestyles. Better choices could lead to a much healthier America, and we will speak often of those choices in
this course.
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