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Unformatted text preview: To all Sci/Geron 255 students: Assignment #1: I just wanted to make a few comments on assignment #1. First the average for the first assignment was roughly 82% for both the Science and Gerontology. This is very good and you all did a very nice job. A few things to watch out for. When you see the word distinguish you should not only define the two terms, but also give the differences between them. This is certainly the case for L.E. and L.S. The life expectancy is increasing while the life span has remained the same for roughly 100,000 years. Most of you got that this year. LE is the average age at death. It would be helpful to think of this as wanting to know the average of the assignment (above). I derived this by adding up everyones mark out of 52 and dividing by the number of people in the class who handed in an assignment. That is quite literally the average. Age at death would be no different. Add up the ages at death of all the people who died in a given population and divide by the number of people who died. Many people indicated it was adding the number of deaths or adding the deaths, this is not the same thing or not as clearly stated as sum or add the ages at death . This is an important concept since you will be calculating a LE for assignment #4. If you substituted one term with another i.e. mean lifespan is the life expectancy, that is fine, but that is not defining either term for me. It is only replacing one term with another. Also Gompertzs 2 parts to mortality. The first part was done well, for the age independent component. The second part it was very important that you didnt just say that there was increased risk of dying with age. That is as you get older the risk of disease and dying increases. This is true but only part of it. What is truly interesting about Gompertz curves and the aging dependent part of mortality is that if you plot the data on a semi log graph (or transform the data to mortality rate) you see that it becomes exponential after the age of 30. That is the mortality rate (or the risk of dying) roughly doubles ever 8 years after the age of 30. This may not seem important but what that means is that there is a uniform process to aging. You would never see this type of exponential increase in the age independent mortality. It means that aging is uniform and regulated. This will become important when we discuss the theories of aging, since it could imply a genetic influence on aging. At the very least it implies that the decrease in functional capacity that occurs in everyone after the age of 30 is uniform (though dictated and modified somewhat by extrinsic factors). So this was the only part I was a stickler on. Also, you havent seen yet, but the incidence of agerelated diseases follows the same pathway as mortality. That is if you look at the incidence of chronic diseases with age you see an exponential increase after the age of 30 (for example risk of cardiovascular disease, cancer etc). This indicates that the aging process and of cardiovascular disease, cancer etc)....
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 Spring '11
 Cheryl
 Biology, Gerontology

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