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CHARTING NORMAL AGING
As recently as a few decades ago, scientists knew little about how people normally change physically as they get older. Medical tests and treatments were based on what was right for a young adult, though most of us are diagnosed and treated medically in middle and later life. Doctors knew the bodies of their older patients were different, but they had to use laboratory standards based on young people for testing and treating seventy-year-olds. The dosages of drugs they gave often seemed too high for their older patients; they had been calibrated on volunteers in their twenties and thirties, when our body is in peak physical shape.
The Baltimore Longitudinal Study of Aging was begun in 1959 to shed light on how we change physiologically as we age. A group of reasonably healthy community-dwelling adults ranging from the teens to the late nineties was recruited. So far, about 650 men and 350 women have volunteered. People who enter the study are asked to make a lifelong commitment. Depending on their age, they return either every year or every two years to spend several days at the Gerontology Research Center in Baltimore answering questions about their health and undergoing tests. At each visit a comprehensive medical history is taken. Volunteers are thoroughly examined physically. Hundreds of capacities are measured, from grip strength to the amount of body fat to how fast the person can respond to a signal. Participants in the study are also given tests of memory and problem solving. Their personalities and mental health are plumbed.
Why doesn’t the National Institute on Aging researchers simply compare how people of different ages function on these tests rather than requiring volunteers to make an ongoing commitment of this magnitude? The reason is that their approach - while demanding - provides a much more accurate picture of how aging occurs. Because each generation is arriving at eighty healthier, comparing today\'s forty-year-olds with today\'s eighty-year-olds would give a grossly inflated picture of the toll the years take. We are much safer if we measure that toll as it actually occurs - in flesh-and-blood human beings.
The Baltimore study has changed medical practice by giving doctors true age norms for interpreting laboratory tests. For instance, it has shown that the blood sugar level used for diagnosing diabetes, while adequate for a younger person, is too low to apply to a person past midlife. The body adjusts to a normal decrease in our ability to metabolize sugar as we get older, and the same laboratory reading that means a person in his twenties is diabetic may not signify diabetic symptoms in someone of sixty-five. Blood pressure that would upset us in a twenty-year-old may even be optimal for health in our seventies. We naturally need a higher blood pressure to circulate blood through arteries that are seventy years old. And the study is teaching doctors to tread more cautiously when they prescribe medicines. Lower dosages are often needed in later life.
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GENERAL HEALTH
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