Death-tests and what epidemiology really is

A few years ago I completed some online test which determined that I will die at the age of 60-something from cancer (or something like that)… To confirm, I googled some death tests and here are the results from today (all clickable, so you can test yourselves):

• I will die in 2072, at the age of 87 (no cause given)
• I will die in 2066, at the age of 81 (cancer)
• I will die in 2058, at the age of age 73 (alcoholism - 10%; cleaning your gun - 6%; alien Abduction - 5%; cancer - 2%)
  

How do they “know” when I will die? Through the power of epidemiology :)

Epidemiology is this wonderful science that can – among other things – statistically estimate the time of your death. How? If you clicked on any of the tests above (I recommend the first one ;)), you will see that they (all) ask a series of questions. Do you smoke? How often do you eat (fresh) fruits and vegetables? Do you have unprotected sex? Do you exercise? And so on…

These are the so called risk factors or determinants of a disease (or, in this case, death). Now, since we already know how certain risk factors are associated with certain diseases, we can calculate the likelihood of you dying from these risk factors... in other words, time of your death (of course, if you believe the result, you might as well believe in Santa).

So, what we got so far: disease and risk factors.

Now, let’s get a bit more serious – what is epidemiology really? Gordis tells us that “epidemiology is the study of how disease is distributed in populations and the factors that influence or determine this distribution”. In other words, there are things out there that threaten populations (diseases) and they spread according to certain factors.

Let me illustrate this point by a clip from Community (NBC TV show):


What does “Chiquita MD” tell us about the disease? It is caused by a “rabies-related pathogen“, it could “take years to take over the world” (1–1.5 to be more exact; just in time for 2012) and it spreads through bites. The army is aware of the issue, that’s why the dean locked everybody inside the school. Quarantine is supposed to ensure that no-one infected gets out (i.e. limiting the spread of the disease). The problem is that if you get bitten, the symptoms do not develop immediately – there is the so-called incubation period, a time between being bitten and actually turning into a zombie. This issue becomes apparent later in the clip when our heroes barricade themselves into the same room without realizing that two of them have already been bitten. People in this preclinical stage of the disease (before the symptoms develop; symptoms indicate the clinical stage of the disease) often act as carriers of the disease since others do not perceive them as infected (often, they themselves do not know they are infected... which is exactly what makes the HIV virus so dangerous - it can take years before the disease becomes apparent).

There is another element of epidemiology we can identify in that clip above – prevention. Gordis explains in his book that there are three types of prevention:

1. Primary (the actual prevention – so you are less likely to get sick in the first place)
2. Secondary (early detection of disease, when it is less severe and complicated to treat)
3. Tertiary (reducing the impact of the disease)

So, when they (in the clip) come up with the idea to lower the temperature – we can call that tertiary prevention (breaking the fever; on the other hand, it is also primary prevention, because it may also kill the virus and stop it from spreading).

Spreading of a disease is another thing epidemiology is greatly interested in. According to Gordis (who else, hehe, the guy wrote our textbook), these are the modes of transmission:

1. Direct ("person-to-person" - like zombies biting people… also vampires :D)
2. Indirect ("common vehicle" - like smoking, contaminated water, etc; or "vector" - a mosquito carrying a disease)

So, zombies are a classic case of person-to-person transmission. Many modern movies try to explain zombies, vampires and werewolves as being infected by a virus… Which makes me think: are we, as a society, becoming too afraid of viruses? It’s one thing to be careful, but to see danger in everything is something else... Could we do something stupid because of that?

For example, should we allow or ban a chemical compound that has been responsible for numerous deaths throughout the history, but is nowadays, among other things, used by big-business as an ingredient in baby food (despite the fact than inhaling a relatively small amount of it could kill a grown man)? If you want to learn more about this chemical compound (dihydrogen monoxide), visit this website. There have been attempts by some politicians to ban this thing, yet they have been unsuccessful... Should we do something about it on a larger scale?

When it comes to actions, we should foremost be aware of real threats. An outbreak of "epidemic" proportions is something we can prepare for, but we cannot live in fear just because "it might happen" (especially since we do not know where "the big one" might come from... do you think dinosaurs were considering allocating some of their resources for advancement of astronomy?). However, there are these silent threats that keep killing us - guess what accounts for about 50% of deaths in America every year? Heart diseases and cancer (according to Gordis). I was not really surprised it was these two, but I was shocked to see they are responsible for half of all deaths.

I would like to use this opportunity to explain some more technical terms. I mentioned "epidemic proportions" earlier. There are, however, three variants (according to Gorids): when a disease is within its usual boundaries (in terms of numbers of cases), it is endemic. When it exceeds the usual number of cases (within a certain geographic area), we call it epidemic. When it affects a large territory (a continent, even the whole world), we talk about a pandemic disease.

Now, let's look at the two killers mentioned above. How would you classify them? Epidemic, because of the numbers? But unless you see these numbers for the first time, you might not really be surprised that much by them. These two diseases have gradually climbed the list of top ten killers (according to Gordis, they were fourth (heart disease) and seventh (cancer) about a 100 years ago), so we might as well call them endemic.

What about obesity? Here is a picture showing its prevalence:

(found at bbc.com)

We could actually call it a pandemic. But then again, the numbers are not really all that surprising and far from the unexpected. On the other hand, calling it an endemic would seem like an understatement...

Despite all this issues with definitions, we can say that we have some big health problems around us. Epidemiology is greatly interested in them (not only the epidemic and pandemic ones) and is constantly looking for ways to improve the health of populations. However, when it comes to proposing policies, we bump into another issue - individual liberties. Should we allow our governments to ban unhealthy foods or should we be free to choose? Many countries have actually gone this far and banned smoking in many places (but they found a "loophole", the second-hand smoking... I've never head of second-hand eating)... Do you think this is the path we should be taking as a society?

The bottom line, I believe, is to be smart and learn from all the research. Remember the death tests? Did you try any of those? How many times did you notice that you chose the "wrong" answer? I mean, we pretty much know what is good and what is bad for us. But we keep doing so many of the bad things. We think we might be "special", just what two of the characters in that Community clip thought... And it is a fact, we are different, we are all special in a way. However, I know that I am not that special, and those death tests reminded me of certain things I need to take care of in my life. Epidemiology became a valuable addition in my life and in fact, it has always been. It's just that now, I am aware of it.