6B Human Development #5 Various body changes occur as adults age....

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Aging 2: How Scientists Study Aging

To help students learn how scientists study aging by reviewing experiments related to the affect of caloric reduction on aging.

This lesson is the second of a two-part series on Science and Aging and is more appropriate for advanced middle-school students (8th graders). It builds on concepts presented in Aging 1: The Science of Aging.

This lesson helps students understand how scientists study aging, and specifically the study of the relationship between aging and caloric reduction. With advancements in health and medicine, along with a better understanding of the aging process, life expectancy for humans keeps increasing. It is probable that the life expectancy of today's middle-school students is going to be longer than the life expectancy of current adults.

There appears to be a maximum life span for each species, including humans. Although some humans live more than a hundred years, most do not; the average length of life, including individuals who die in childhood, ranges from as low as 35 in some populations to as high as 75 in most industrialized nations. The high averages are due mostly to low death rates for infants and children but also to better sanitation, diet, and hygiene for most people, and to improved medical care for the old.

Life expectancy also varies among different socioeconomic groups and by sex. The most common causes of death differ for various age, ethnic, and economic groups. In the United States, for example, fatal traffic accidents are most common among young males, heart disease causes more deaths in men than women, and infectious diseases and homicides cause more deaths among the poor than among the rich. (Science for All Americans, p. 76.)

Students should begin to understand that there is both a physiological and emotional aspect to the aging process and that these two aspects are related. The aging process in humans is associated not only with changes in the hormonal system but also with disease and injury, diet, mutations arising and accumulating in the cells, wear on tissues such as weight bearing joints, psychological factors, and exposure to harmful substances. Sometimes diseases that appear late in life will affect brain function, including memory and personality. In addition, diminished physical capacity and loss of one's accustomed social role can result in anxiety or depression. On the other hand, many old people are able to get along quite well, living out independent and active lives, without prolonged periods of disability.

In this lesson, students will learn explore a website to learn how scientists are studying the relationship between aging and caloric restriction. This lesson should help students generally understand some of the factors involved in aging, but it is by no means comprehensive.

Students can follow-up with more in-depth studies, including related concepts found in the following Science NetLinks lessons:

• Nearsightedness
  
• Sanitation and Human Health
  

Materials:

• How Scientists Study Aging student sheet
• How Scientists Study Aging teacher sheet

Continue discussing the concepts introduced in the previous lesson, Aging 1: The Science of Aging.

Ask students the following questions to initiate the discussion:

• Why do you think people have always been so fascinated with trying to stay young?
• Do you think you can have any control over how you age?
• What factors do you think may have an effect on how long people live? Remember to consider both emotional, as well as physical factors. (Factors may include nutrition, economic conditions, environmental conditions, and genetics.)
• What types of studies do you think scientists would use to determine if there was a relationship between these factors and aging? (Cross-sectional and longitudinal studies of populations and studies on animals.)
• How might nutrition affect aging? How might scientists study the effects of nutrition on aging?

Next, ask students to explore Defying Death, on the Why Files website. Ask students to take notes related to the questions in the How Scientists Study Aging student sheet.

Then, lead students through a discussion about aging by asking the questions from the student sheet. (Please see the How Scientists Study Aging teacher sheet for the questions from the student sheet with suggested responses.)

Have students write an informal essay on the topic below. They should review their notes from The Science of Aging student sheet.

Compare the research techniques used in the studies of caloric restriction with the cross-sectional and longitudinal studies discussed in the Secrets of Aging. You should define each type of study and give an example of each. Then answer this question: What can we learn by studying humans directly and what can we learn from studies of other animals and how that might apply to humans?

(The caloric restriction experiments used animals, such as rats, mice, fruit flies, and monkeys. The cross-sectional and longitudinal studies observed how humans age. By studying humans in cross-sectional and longitudinal studies, we can observe how they change, both physiologically and emotionally, from generation to generation or how one generation changes over a long period of time. By studying animals, we can learn how their different physiological systems are affected and try to draw conclusions about how this would affect humans. It is difficult to study emotional aspects of aging in animals.)

To further explore topics related to science and aging, continue with the Science NetLinks lesson entitled Nearsightedness.

The purpose of this lesson is to help students develop an understanding of why scientific investigations may yield varying results. This lesson gives students the opportunity to examine the nature of scientific research in the context of research pertaining to myopia, or nearsightedness.

The following Internet resources can be used to further explore the topics related to science and aging:

• Science of Aging on PBS looks at the discovery of a set of "anti-aging" genes in animals that—when manipulated—have similar life-extending effects as calorie-restrictive diets.
• Live, fast, die old, is an article summarizing some of the research about the relationship between eating less and living longer.
• Life Expectancy, a learning module from the World Bank, contains learning activities that look at life expectancies around the world. It discusses why life expectancy has risen in many countries but not all in others.

Created : 01/29/2002