Late adulthood - 60s and above - is a recent conception in developmental psychology because just a century ago (in the 1900s), the human race die 30 years younger than today's average. On average, life expectancy in the US rose from 47 years old to 77 years old - 80 years old in women, and 73 years old in men. In order to incorporate the age range of 60s and above, "old age" was conceptualized. However, the rising life expectancy in human race pose challenge into charting the developmental changes that take place in old age. Among the common physical changes observed in late adulthood are the following:
- Weight Decline. If in middle age, adults tend to gain weight due to increasing fat deposits in the body; in old age, adults begin to lose weight as muscle tissue in the body die. It is not clear, however, if in old age, fat burn alongside significant muscle tissue loss, but presumably because of lower activity level and lower food consumption, fat get used up faster than normal, thus also lowering the amount of fat in the body.
- Bone Tissue Loss. Not only the muscles die out, but also the bone tissues. Declining estrogen production in menopausal women during middle-age could probably explain why 2/3 of women in old age have osteoporosis.
- Stopped Dendritic Growth. At old age, dendrites (or the communication antennae of our brain cells) grow at significantly lower rate than normal, and then stop growing at the 90s.
- Chronic Diseases. Chronic diseases - those that start slow but last long - become common in late adulthood. The most common chronic disease among old-age adults in the US is arthritis, while the second most common is hypertension (or rising blood pressure). Furthermore, old-age adults have increased risk for Alzheimer's Disease, and the percentage doubles every after 5 years. Alzheimer's Disease is characterized with low levels of acetylcholine in the brain, plaque formation in the brain's blood vessels, and tangles (or protein bundles) that impair neuronal activity in the brain. These characteristics are normal in aging, but they are more pronounced in those who have Alzheimer's Disease. In order to compensate for the low levels of ACh in the brain, the drug Aricept is oftentimes prescribed by doctors to block chemicals that pervasively destroy Ach.
Two fundamental theories of aging are currently being adopted to explain how people age and why adults tend to show decline in their physical health. Haylick's Cellular-Clock Theory explains that cellular division is related to age, and that there is less division happening in middle and late adulthood. His theory served as the basis for calculating life span across species, placing us humans in a "deadline" at 120 years of age. One possible reason why cellular division slows down as we age is because of the progressive reduction of telomeres. Telomeres serve as plugs that protect the tips or the ends of the chromosomes in the body. As body cells divide, telomeres reduce in length and strength in order to keep the chromosomes from breaking apart. Reduced telomeres is linked with inability to recover from stress and increased risk for cancer. One promising thought, though, about the cellular-clock theory is the possibility of artificially altering cellular activity in order to raise life span, but this speculation is still far from truth. On the other hand, Knight's Free Radical Theory explains that free radicals, unstable oxygen molecules that freely float in the body, damage DNA and other cellular structures. His theory showed how proper nutrition and exercise contribute to increasing life expectancy in humans.
Cognitive Development in Late Adulthood
Old adults, like middle-age ones, show decline in information-processing speed, but in a much-faster rate. Memory for names and locations decline. Information recall slows down, but most are still able to retrieve. Because of this, old adults, when forced to solve problems, manipulate information instead of relying to casual recall.
Socioemotional Development in Late Adulthood
Old-age adults tend to be selective in their social interactions - maximizing emotional satisfaction, and minimizing emotional risks. Generally, they prefer visits from family, relatives and close friends. The importance old-age adults place upon emotions is supported by research. Carstensen and Turk-Charles (1994) found that after reading a passage from a popular novel to 20-83 year-olds, younger adults perform better in recalling neutral material than older ones, but that older adults perform better than younger ones when the passage is emotional by nature. This means that old adults are more attuned towards emotional information than young adults. Furthermore, in another study, it was shown that old adults get affected with negative emotions more than younger ones (Carstensen, Pasupathi & Mayr, 1998).