In this course of study we will be focusing on human aging, but of course all living things have a life time. In order to study aging scientists often look to other forms of life, both animals and plants. The reason for this is simple, humans along with most mammals live too long!
Imagine being a scientist who is studying the aging of individual people. If you start studying a person at his birth it is very likely your lifetime will end before his does. Of course groups of researchers have worked together to complete this type of research. An example of this is the Framingham Heart Study, which was begun in 1948 with 5209 men and women and continues today. This study has expanded to include the children and grandchildren of the original participants and also to include additional participants to create a more diverse study group. While the researchers have had to be patient the study has greatly increased our understanding of cardiovascular disease. This research method is referred to as longitudinal study.
Cross-sectional studies are more commonly used to study humans. These studies compare a measureable parameter across different groups of people. For example, a simple study could compare the average blood pressure of people between the ages of 20 and 30 to people between the ages of 40 and 50. This type of study can be done relative quickly and cheaply with large groups of people. This disadvantage is that is very difficult to differentiate age-related changes from the effects of numerous environmental and social factors.
Still another type of study involves lower animals. In studies which use lower animals researchers can more easily control genetic variability, environmental factors, and social factors. These are huge advantageous to the scientific process, but of course we are primarily interested in human aging. Scientists must be careful not to extrapolate findings which may or may not be applicable to humans.