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200 PILLAR 2 Development and Learningespecially if the person smokes (which shortens telomeres), is under stress, or is overweight. Without perfect telomeres, the chromosomal cells may die without an identical genetic replacement.14,15 So, frayed telomeres in the chromosomal cells necessary for memory could mean that older people require more time to react, remember names, and solve puzzles.16,17 Also, portions of the brain start to atrophy, or waste away.18 If you live to be 80, your brain will weigh several ounces less than it does now. Cell loss in the memory regions of the brain is particularly detrimental.You can compensate for lost brain cells and neural connections by remaining physically and mentally active.19,20 Exercise appears to foster brain cell development while helping prevent heart disease and obesity.21 Exercise may not be the fountain of youth, but it is usually a fountain of health.Diseases Related to AgingToward the end of his life, the United States%u2019 fortieth president, Ronald Reagan, wrote a final letter to the American people stating, %u201cI now begin the journey that will lead me into the sunset of my life.%u201d At age 83, Reagan was telling the world he had Alzheimer%u2019s disease, a progressive and irreversible brain disorder characterized by gradual deterioration of memory, reasoning, language, and, ultimately, physical functioning.The memory loss associated with this disease is caused by deteriorating neurons that produce a vital brain chemical (acetylcholine). Without this chemical, thinking and memory are greatly impaired. Almost 3 percent of the world%u2019s population develops Alzheimer%u2019s disease by age 75.Certain drugs can slow down the advance of Alzheimer%u2019s disease, and newer drugs on the market show great promise, but there is no known cure.22 Research shows that challenged and active minds%u2014that is, the minds of people who read a lot and continue to learn across the life span%u2014are at lower risk for Alzheimer%u2019s onset.23 By comparison, inactive and obese individuals are more likely to experience Alzheimer%u2019s disease.24 Gene abnormalities and dead tissue on the ends of neurons (which prevent normal functioning) have been linked to Alzheimer%u2019s disease, and a simple blood test can now be used to at least partially determine the likelihood of developing the disease.25Alzheimer%u2019s disease is just one cause of neurocognitive disorder (NCD), a condition often referred to as dementia when it occurs in older adults. Dementia can be also caused by alcoholism, tumor, strokes, or anything else that results in a major loss of brain cells. The likelihood of dementia increases with age (Figure 12.2).26Not every older adult who forgets song titles, passwords, or the location of those misplaced keys has dementia. Some memory loss is a normal part of aging. And the news about cognitive functioning isn%u2019t all bad, either. Look next at what happens to our thinking processes as we age.Gwen Shockey/Science SourceGene Abnormalities and Alzheimer%u2019s DiseaseDead tissue on the end of some chromosomes can alter genetic functioning and has been linked to Alzheimer%u2019s disease.Alzheimer%u2019s disease A progressive and irreversible brain disorder characterized by gradual deterioration of memory, reasoning, language, and, finally, physical functioning.dementia An acquired (that is, not lifelong) decline in cognitive functioning, often related to Alzheimer%u2019s disease, brain injury or disease, or substance abuse.40%3020100Percentagewith dementiaAge group60%u201364 90%u20139565%u20136970%u20137485%u20138980%u20138475%u201379FIGURE 12.2 Dementia and AgeThe likelihood of dementia increases as we grow older. (Data from Jorm et al., 1987, based on 22 studies in industrialized nations.)%u00a9 Bedford, Freeman & Worth Publishers. For review purposes only. Do not distribute.