I. Why is epidemiologic surveillance important for public health and what role would it play if th

I. Why is epidemiologic surveillance important for public health and what role would it play if there were a bioterrorist attack?

II. How has epidemiology contributed to people’s understanding of heart disease and lung cancer?

III. Visit the Web site of the Framingham Heart Study, (www.framingham.com/heart).

What are the most recent findings from this cohort study? Differentiate between incidence and prevalence. Which one do you believe is more useful in identifying the cause of a disease? Give examples for each

I. Why is epidemiologic surveillance important for public health and what role would it play if there were a bioterrorist attack?

According to WHO1, Public health (epidemiologic) surveillance is the continuous, systematic collection, analysis and interpretation of health-related data needed for the planning, implementation, and evaluation of public health practice.

This is important as it intrinsically promotes the very definition of Public Health, which is the totality of all evidence-based public and private efforts that preserve and promote health and prevent disease, disability and death2. The fact that it is continuous and systematic in nature is most important as new risks and diseases are emerging and changing every day.

If there was a bioterrorist attack, epidemiologic surveillance (ES) would serve as an early warning system for the pending health scare/emergency. ES would be responsible for documenting the impacts of interventions and or tracking progress towards specified goals. ES would also monitor and clarify the epidemiology of health problems/ bioterrorist attacks so that priorities are set and public health policies and strategies are informed. ES would be responsible for establishing a diagnosis through surveying certain trends reported on a large scale in the clinical setting.

Using the example of anthrax, usually patients will start out with nonspecific symptomatology that can surpass a week before the grave form of the disease sets in. This group of incidences would be labeled as potential ‘true positives’ and then reported to the health department and evaluated for atypical presentations. Epidemiologists would then report as to whether further investigation is justified and patients would go through a series of laboratory tests. In less than a day, with the lab results in hand, a presumptive diagnosis of anthrax (in this example) would be given and a full-scale response prompted.

II. How has epidemiology contributed to people’s understanding of heart disease and lung cancer?

Epidemiology has to do with helping people understand the burden of a disease. In particular, regarding heart disease and lung cancer, epidemiology has helped us learn that these disorders are the leading causes of death and major causes of disability and rising health costs worldwide1,2. We now know that these diseases are linked by common lifestyle determinants such as diet, physical activity and tobacco use. We have also learned that there are variations in these disease rates by ethnicity, geography and even socioeconomic status-because of at-risk behaviors associated with the different groups. Epidemiology has informed us of the risk factors involved in acquiring these diseases and has shed light on the common symptoms of these diseases and how to prevent/reduce the prevalence of these illnesses where possible.

III. Visit the Web site of the Framingham Heart Study, (www.framingham.com/heart).

What are the most recent findings from this cohort study? Differentiate between incidence and prevalence. Which one do you believe is more useful in identifying the cause of a disease? Give examples for each

After visiting the recommended website of the Framingham Heart Study (FHS),

( www.framingham.com/heart ), the last update regarding recent findings was done in 20051, where an Offspring Study based report indicated an increase of up to 45 percent for risk of heart attack, stroke or arterial disease may occur in middle-aged people with a sibling who suffered a similar cardiovascular event. Upon further research, I came across a more updated website (2016), www.framinghamheartstudy.org, that gives a timeline of updates up until 2010. From that year, the most recent findings are as follows2:

Sleep apnea is tied to an increased risk of stroke. The FHS researchers identified additional genes that may play a role in Alzheimer’s disease, and linked abdominal fat with smaller, older brains in middle-aged adults. They also found genes that linked pubertal timing and body fat in women. It was identified that having first-degree relatives with atrial fibrillation is associated with an increased risk for this disorder. FHS researchers contributed to discovering hundreds of new genes underlying major heart disease risk factors—body mass index, blood cholesterol, cigarette smoking, blood pressure and glucose/diabetes. Lastly, the first definitive evidence that occurrence of stroke by age 65 years in a parent, increased risk of stroke in offspring by 3­fold was discovered.

Incidence rate is the proportion of individuals developing a new disease during a period of time.

Prevalence rate is the proportion of individuals with existing disease at a point or period in time.

With regards to which one I believe is more useful in identifying the cause of a disease, I would have to say that that depends on the disease. I say this because with a communicable disease like Influenza (Flu) that is acute (short in duration), Incidence rate would be more useful, as the prevalence quickly fades. Incidence rates can be calculated only over a period of time, not at a single point. On the other hand, Prevalence focuses more on chronic diseases, such as Hypertension, cancers, etc. Prevalence can be calculated at a particular point or period in time.

IV. The three major types of epidemiologic studies are:

1. Cross-sectional, also known as a prevalence study. In this type, the presence or absence of disease and other variables are determined in each member of the study population or in a representative sample at a particular time. The co-occurrence of a variable and the disease can be examined. Disease prevalence rather than incidence is recorded. The temporal sequence of cause and effect cannot usually be determined in a cross-sectional study1. E.g., who in the community now has treatment-resistant TB. I think that this is the study that would most likely provide valid results, as this is a prevalence study and it is usually limited to a particular time. Therefore, there’s no guessing here, you either have the disease (As a result of labs/screening tests and confirmatory tests, etc.) or you don’t. For that reason, I also believe that this is likely to yield an answer in the shortest period of time. There’s no real looking back or following subjects forward over a period of time.

2. Case-control studies2 identify a group of people with the disease and compare them with a suitable comparison group without the disease. It is almost always retrospective. E.g. comparing cases of treatment resistant TB with cases of nonresistant TB. In this type of study, disease vs. non-disease is the starting point. It cannot assess incidence or prevalence of disease, but can help determine causal relationships. It is very useful for studying conditions with very low incidence or prevalence.

3. In a Cohort study2 a population group is identified who has been exposed to a risk factor, is followed over time and compared with a group not exposed to the risk factor. This study is prospective; subjects are tracked forward in time. Incidence and causal relationships can be determined. Must follow population long enough for incidence to appear. Outcome is disease incidence in each group, e.g., following a prison inmate population and marking the development of treatment-resistant TB.

1Steven R. Daugherty, Ph.D Epidemiology and ethics, Kaplan Medical USMLE lecture notes, 2011

2Riegelman and Kirkwood, Public health 101, 2015 p. 27-28