Among the middle-aged adults who rate their health unfavorably,

chapter 15 Physical and Cognitive Development in Middle Adulthood

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A principal dancer at the Grand Opera of Paris teaches a master class for young professional dancers, transferring knowledge, skill, and passion for his art to a new generation. In middle adulthood, expertise reaches its height.

chapter outline

· PHYSICAL DEVELOPMENT

· Physical Changes

· Vision

· Hearing

· Skin

· Muscle–Fat Makeup

· Skeleton

· Reproductive System

· ■ BIOLOGY AND ENVIRONMENT Anti-Aging Effects of Dietary Calorie Restriction

· ■ CULTURAL INFLUENCES Menopause as a Biocultural Event

· Health and Fitness

· Sexuality

· Illness and Disability

· Hostility and Anger

· Adapting to the Physical Challenges of Midlife

· Stress Management

· Exercise

· An Optimistic Outlook

· Gender and Aging: A Double Standard

· COGNITIVE DEVELOPMENT

Changes in Mental Abilities

· Cohort Effects

· Crystallized and Fluid Intelligence

· Individual and Group Differences

· Information Processing

· Speed of Processing

· Attention

· Memory

· Practical Problem Solving and Expertise

· Creativity

· Information Processing in Context

· ■ SOCIAL ISSUES: EDUCATION The Art of Acting Improves Memory in Older Adults

· Vocational Life and Cognitive Development

· Adult Learners: Becoming a Student in Midlife

· Characteristics of Returning Students

· Supporting Returning Students

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On a snowy December evening, Devin and Trisha sat down to read the holiday cards piled high on the kitchen counter. Devin’s 55th birthday had just passed; Trisha would turn 48 in a few weeks. During the past year, they had celebrated their 24th wedding anniversary. These milestones, along with the annual updates they received from friends, brought the changes of midlife into bold relief.

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Instead of new births, children starting school, or a first promotion at work, holiday cards and letters sounded new themes. Jewel’s recap of the past year reflected growing awareness of a finite lifespan, one in which time had become more precious. She wrote:

· My mood has been lighter ever since my birthday. There was some burden I laid down by turning 49. My mother passed away when she was 48, so it all feels like a gift now. Blessed be!

George and Anya reported on their son’s graduation from law school and their daughter Michelle’s first year of university:

· Anya is filling the gap created by the children’s departure by returning to college for a nursing degree. After enrolling this fall, she was surprised to find herself in the same psychology class as Michelle. At first, Anya worried about handling the academic work, but after a semester of success, she’s feeling more confident.

Tim’s message reflected continuing robust health, acceptance of physical changes, and a new burden: caring for aging parents—a firm reminder of the limits of the lifespan:

· I used to be a good basketball player in college, but recently I noticed that my 20-year-old nephew, Brent, can dribble and shoot circles around me. It must be my age! But I ran our city marathon in September and came in seventh in the over-50 division. Brent ran, too, but he opted out a few miles short of the finish line to get some pizza while I pressed on. That must be my age, too!

The saddest news is that my dad had a bad stroke. His mind is clear, but his body is partially paralyzed. It’s really upsetting because he was getting to enjoy the computer I gave him, and it was so upbeat to talk with him about it in the months before the stroke.

Middle adulthood, which begins around age 40 and ends at about 65, is marked by narrowing life options and a shrinking future as children leave home and career paths become more determined. In other ways, middle age is hard to define because wide variations in attitudes and behaviors exist. Some individuals seem physically and mentally young at age 65—active and optimistic, with a sense of serenity and stability. Others feel old at age 40—as if their lives had peaked and were on a downhill course.

Another reason middle adulthood eludes definition is that it is a contemporary phenomenon. Before the twentieth century, only a brief interval separated the tasks of early adulthood from those of old age. Women were often widows by their mid-fifties, before their youngest child left home. And harsh living conditions led people to accept a ravaged body as a natural part of life. As life expectancy—and, with it, health and vigor—increased over the past century, adults became more aware of their own aging and mortality.

In this chapter, we trace physical and cognitive development in midlife. In both domains, we will encounter not just progressive declines but also sustained performance and compensating gains. As in earlier chapters, we will see that change occurs in manifold ways. Besides heredity and biological aging, our personal approach to passing years combines with family, community, and cultural contexts to affect the way we age.

PHYSICAL DEVELOPMENT

Physical development in middle adulthood is a continuation of the gradual changes under way in early adulthood. Even the most vigorous adults notice an older body when looking in the mirror or at family photos. Hair grays and thins, new lines appear on the face, and a fuller, less youthful body shape is evident. During midlife, most individuals begin to experience life-threatening health episodes—if not in themselves, then in their partners and friends. And a change in time orientation, from “years since birth” to “years left to live,” adds to consciousness of aging (Neugarten, 1968b ).

These factors lead to a revised physical self-image, with somewhat less emphasis on hoped-for gains and more on feared declines (Bybee & Wells, 2003 ; Frazier, Barreto, & Newman, 2012 ). Prominent concerns of 40- to 65-year-olds include getting a fatal disease, being too ill to maintain independence, and losing mental capacities. Unfortunately, many middle-aged adults fail to embrace realistic alternatives—becoming more physically fit and developing into healthy, energetic older adults. Although certain aspects of aging cannot be controlled, people can do much to promote physical vigor and good health in midlife.

image4 Physical Changes

As she dressed for work one morning, Trisha remarked jokingly to Devin, “I think I’ll leave the dust on the mirror so I can’t see the wrinkles and gray hairs.” Catching sight of her image, she continued in a more serious tone. “And look at this fat—it just doesn’t want to go! I need to fit some regular exercise into my life.” In response, Devin glanced soberly at his own enlarged midriff.

At breakfast, Devin took his glasses on and off and squinted while reading the paper. “Trish—what’s the eye doctor’s phone number? I’ve got to get these bifocals adjusted again.” As they conversed between the kitchen and the adjoining den, Devin sometimes asked Trisha to repeat herself. And he kept turning up the radio and TV volume. “Does it need to be that loud?” Trisha would ask. Apparently Devin couldn’t hear as clearly as before.

In the following sections, we look closely at the major physical changes of midlife. As we do so, you may find it helpful to refer back to Table 13.1 on page 435 , which provides a summary.

Vision

By the forties, difficulty reading small print is common, due to thickening of the lens combined with weakening of the muscle that enables the eye to accommodate (adjust its focus) to nearby objects. As new fibers appear on the surface of the lens, they compress older fibers toward the center, creating a thicker, denser, less pliable structure that eventually cannot be transformed at all. By age 50, the accommodative ability of the lens is one-sixth of what it was at age 20. Around age 60, the lens loses its capacity to adjust to objects at varying distances entirely, a condition called presbyopia (literally, “old eyes”). As the lens enlarges, the eye rapidly becomes more farsighted between ages 40 and 60 (Charman, 2008 ). Corrective lenses—or, for nearsighted people, bifocals—ease reading problems.

A second set of changes limits ability to see in dim light, which declines at twice the rate of daylight vision (Jackson & Owsley, 2000 ). Throughout adulthood, the size of the pupil shrinks and the lens yellows. In addition, starting at age 40, the vitreous (transparent gelatin-like substance that fills the eye) develops opaque areas, reducing the amount of light reaching the retina. Changes in the lens and vitreous also cause light to scatter within the eye, increasing sensitivity to glare. Devin had always enjoyed driving at night, but now he sometimes had trouble making out signs and moving objects (Owsley, 2011 ). And his vision was more disrupted by bright light sources, such as headlights of oncoming cars. Yellowing of the lens and increasing density of the vitreous also limit color discrimination, especially at the green–blue–violet end of the spectrum (Paramei, 2012 ). Occasionally, Devin had to ask whether his sport coat, tie, and socks matched.

Besides structural changes in the eye, neural changes in the visual system occur. Gradual loss of rods and cones (light- and color-receptor cells) in the retina and of neurons in the optic nerve (the pathway between the retina and the cerebral cortex) contributes to visual declines. By midlife, half the rods (which enable vision in dim light) are lost (Owsley, 2011 ). And because rods secrete substances necessary for survival of cones (which enable daylight and color vision), gradual loss of cones follows.

Middle-aged adults are at increased risk of glaucoma , a disease in which poor fluid drainage leads to a buildup of pressure within the eye, damaging the optic nerve. Glaucoma affects nearly 2 percent of people over age 40, more often women than men. It typically progresses without noticeable symptoms and is a leading cause of blindness. Heredity contributes to glaucoma, which runs in families: Siblings of people with the disease have a tenfold increased risk, and it occurs three to four times as often in African Americans and Hispanics as in Caucasians (Guedes, Tsai, & Loewen, 2011 ; Kwon et al., 2009 ). Starting in midlife, eye exams should include a glaucoma test. Drugs that promote release of fluid and surgery to open blocked drainage channels prevent vision loss.

Hearing

An estimated 14 percent of Americans between ages 45 and 64 suffer from hearing loss, often resulting from adult-onset hearing impairments (Center for Hearing and Communication, 2012 ). Although some conditions run in families and may be hereditary, most are age-related, a condition called presbycusis (“old hearing”).

As we age, inner-ear structures that transform mechanical sound waves into neural impulses deteriorate through natural cell death or reduced blood supply caused by atherosclerosis. Processing of neural messages in the auditory cortex also declines. Age-related cognitive changes—in processing speed, attention, and memory—that we will take up shortly are also associated with hearing loss (Lin et al., 2011 ). The first sign, around age 50, is a noticeable decline in sensitivity to high-frequency sounds, which gradually extends to all frequencies. Late in life, human speech becomes more difficult to make out, especially rapid speech and speech against a background of voices (Humes et al., 2012 ). Still, throughout middle adulthood, most people hear reasonably well across a wide frequency range. And African tribal peoples display little age-related hearing loss (Jarvis & van Heerden, 1967 ; Rosen, Bergman, & Plester, 1962 ). These findings suggest factors other than biological aging are involved.

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A worker uses a grinder to smooth a metal surface in a steel manufacturing facility. Men’s hearing declines more rapidly than women’s, a difference associated with several factors, including intense noise in some male-dominated occupations.

Men’s hearing tends to decline earlier and more rapidly than women’s, a difference associated with cigarette smoking, intense noise and chemical pollutants in some male-dominated occupations, and (at older ages) high blood pressure and cerebrovascular disease, or strokes that damage brain tissue (Heltzner et al., 2005 ; Van Eyken, Van Camp, & Van Laer, 2007 ). Government regulations requiring industries to implement such safeguards as noise monitoring, provision of earplugs, pollution control, and regular hearing tests have greatly reduced hearing damage, but some employers do not comply fully (Daniell et al., 2006 ; Ohlemiller, 2008 ).

Most middle-aged and elderly people with hearing difficulties benefit from sound amplification with hearing aids. When perception of the human voice is affected, speaking to the person patiently, clearly, and with good eye contact, in an environment with reduced background noise, aids understanding.

Skin

Our skin consists of three layers: (1) the epidermis, or outer protective layer, where new skin cells are constantly produced; (2) the dermis, or middle supportive layer, consisting of connective tissue that stretches and bounces back, giving the skin flexibility; and (3) the hypodermis, an inner fatty layer that adds to the soft lines and shape of the skin. As we age, the epidermis becomes less firmly attached to the dermis, fibers in the dermis thin, cells in both the epidermis and dermis decline in water content, and fat in the hypodermis diminishes, leading the skin to wrinkle, loosen, and feel dry.

In the thirties, lines develop on the forehead as a result of smiling, furrowing the brow, and other facial expressions. In the forties, these become more pronounced, and “crow’s-feet” appear around the eyes. Gradually, the skin loses elasticity and begins to sag, especially on the face, arms, and legs (Khavkin & Ellis, 2011 ). After age 50, “age spots,” collections of pigment under the skin, increase. Blood vessels in the skin become more visible as the fatty layer thins.

Because sun exposure hastens wrinkling and spotting, individuals who have spent much time outdoors without proper skin protection look older than their contemporaries. And partly because the dermis of women is not as thick as that of men, women’s skin ages more quickly (Makrantonaki & Xouboulis, 2007 ).

Muscle–Fat Makeup

As Trisha and Devin make clear, weight gain—“middle-age spread”—is a concern for both men and women. A common pattern of change is an increase in body fat and a loss of lean body mass (muscle and bone). The rise in fat largely affects the torso and occurs as fatty deposits within the body cavity; as noted earlier, fat beneath the skin on the limbs declines. On average, size of the abdomen increases 7 to 14 percent. Although a large portion is due to weight gain, age-related changes in muscle–fat makeup also contribute (Stevens, Katz, & Huxley, 2010 ). In addition, sex differences in fat distribution appear. Men accumulate more on the back and upper abdomen, women around the waist and upper arms (Sowers et al., 2007 ). Muscle mass declines very gradually in the forties and fifties, largely due to atrophy of fast-twitch fibers, responsible for speed and explosive strength.

Yet, as indicated in Chapter 13 , large weight gain and loss of muscle power are not inevitable. With age, people must gradually reduce caloric intake to adjust for the age-related decline in basal metabolic rate (see page 440 ). In a longitudinal study of nearly 30,000 U.S. 50- to 79-year-old women diverse in SES and ethnicity, a low-fat diet involving increased consumption of vegetables, fruits, and grains was associated with greater initial weight loss and success at maintaining that loss over a seven-year period (Howard et al., 2006 ). In nonhuman animals, dietary restraint dramatically increases longevity while sustaining health and vitality. Currently, researchers are identifying the biological mechanisms involved and studying their relevance to humans (see the Biology and Environment box on the following page).

Furthermore, weight-bearing exercise that includes resistance training (placing a moderately stressful load on the muscles) can offset both excess weight and muscle loss. Within the same individual, strength varies between often-used and little-used muscles (Macaluso & De Vito, 2004 ; Rivlin, 2007 ). Consider Devin’s 57-year-old friend Tim, who for years has ridden his bike to and from work and jogged on weekends, averaging an hour of vigorous activity per day. Like many endurance athletes, he maintained the same weight and muscular physique throughout early and middle adulthood.

Skeleton

As new cells accumulate on their outer layers, the bones broaden, but their mineral content declines, so they become more porous. This leads to a gradual loss in bone density that begins around age 40 and accelerates in the fifties, especially among women (Clarke & Khosla, 2010 ). Women’s reserve of bone minerals is lower than men’s to begin with. And following menopause, the favorable impact of estrogen on bone mineral absorption is lost. Reduction in bone density during adulthood is substantial—about 8 to 12 percent in men and 20 to 30 percent in women (Seeman, 2008 ).

Loss of bone strength causes the disks in the spinal column to collapse. Consequently, height may drop by as much as 1 inch by age 60, a change that will hasten thereafter. In addition, the weakened bones cannot support as much load: They fracture more easily and heal more slowly. A healthy lifestyle—including weight-bearing exercise, adequate calcium and vitamin D intake, and avoidance of smoking and heavy alcohol consumption—can slow bone loss in postmenopausal women by as much as 30 to 50 percent (Cooper et al., 2009 ).

When bone loss is very great, it leads to a debilitating disorder called osteoporosis. We will take up this condition shortly when we consider illness and disability.

Reproductive System

The midlife transition in which fertility declines is called the climacteric. In women, it brings an end to reproductive capacity; in men, by contrast, fertility diminishes but is retained.

Reproductive changes in Women.

The changes involved in women’s climacteric occur gradually over a 10-year period, during which the production of estrogen drops. As a result, the number of days in a woman’s monthly cycle shortens from about 28 in her twenties and thirties to perhaps 23 by her late forties, and her cycles become more irregular. In some, ova are not released; when they are, more are defective (see Chapter 2 , page 53 ). The climacteric concludes with menopause , the end of menstruation and reproductive capacity. This occurs, on average, in the early fifties among North American, European, and East Asian women, although the age range extends from the late thirties to the late fifties (Avis, Crawford, & Johannes, 2002 ; Rossi, 2005 ). Women who smoke or who have not borne children tend to reach menopause earlier.

Following menopause, estrogen declines further, causing the reproductive organs to shrink in size, the genitals to be less easily stimulated, and the vagina to lubricate more slowly during arousal. As a result, complaints about sexual functioning increase, with about 35 to 40 percent of women reporting difficulties, especially among those with health problems or whose partners have sexual performance difficulties (Lindau et al., 2007 ; Walsh & Berman, 2004 ). The drop in estrogen also contributes to decreased elasticity of the skin and loss of bone mass. Also lost is estrogen’s ability to help protect against accumulation of plaque on the walls of the arteries, by boosting “good cholesterol” (high-density lipoprotein).

The period leading up to and following menopause is often accompanied by emotional and physical symptoms, including mood fluctuations and hot flashes—sensations of warmth accompanied by a rise in body temperature and redness in the face, neck, and chest, followed by sweating. Hot flashes—which may occur during the day and also, as night sweats, during sleep—affect more than 50 percent of women in Western industrialized nations (Nelson, 2008 ). Typically, they are not severe: Only about 1 in 12 women experiences them every day.

Biology and Environment Anti-Aging Effects of Dietary Calorie Restriction

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An Okinawan grandfather and grandson enjoy an afternoon of kite flying. Before World War II, residents of Okinawa consumed a restricted diet that was associated with health benefits and longer life. Recent generations no longer show these advantages, possibly due to the introduction of Westernized food to Okinawa.

For nearly 70 years, scientists have known that dietary calorie restriction in nonprimate animals slows aging while maintaining good health and body functions. Rats and mice fed 30 to 40 percent fewer calories than they would freely eat beginning in early life show various physiological health benefits, lower incidence of chronic diseases, and a 60 percent increase in length of life (Fontana, 2009 ). Mild to moderate calorie restriction begun after rodents reach physical maturity also slows aging and extends longevity, though to a lesser extent. Other studies reveal similar dietary-restriction effects in mice, fleas, spiders, worms, fish, and yeast.

Nonhuman Primate Research

Would primates, especially humans, also benefit from a restricted diet? Researchers have been tracking health indicators in rhesus monkeys after placing some on regimens of 30 percent reduced calories at young, middle, and older ages. More than two decades of longitudinal findings revealed that, compared with freely eating controls, dietary-restricted monkeys were smaller but not overly thin. They accumulated body fat differently—less on the torso, a type of fat distribution that reduces middle-aged humans’ risk of heart disease.

Calorie-restricted monkeys also had a lower body temperature and basal metabolic rate—changes that suggest they shifted physiological processes away from growth to life-maintaining functions. Consequently, like calorie-restricted rodents, they seemed better able to withstand severe physical stress, such as surgery and infectious disease (Weindruch et al., 2001 ).

Among physiological processes mediating these benefits, two seem most powerful. First, calorie restriction inhibited production of free radicals, thereby limiting cellular deterioration, which contributes to many diseases of aging (see page 433 in Chapter 13 ) (Carter et al., 2007 ; Yu, 2006 ). Second, calorie restriction reduced blood glucose and improved insulin sensitivity, offering protection against diabetes and cardiovascular disease. Lower blood pressure and cholesterol and a high ratio of “good” to “bad” cholesterol in calorie-restricted primates strengthened these effects (Fontana, 2008 ).

Nevertheless, long-term tracking of the monkeys’ age of death revealed no difference in length of survival between the calorie-restricted and control groups, regardless of the age at which restriction began. Limiting food intake delayed the onset of age-related diseases, including cancer, cardiovascular disease, and arthritis, but it did not extend the monkeys’ longevity (Mattison et al., 2012 ). In sum, the calorie-restricted monkeys benefited from more years of healthy life, not from an extended lifespan.

Human Research

Prior to World War II, residents of the island of Okinawa consumed an average of 20 percent fewer calories (while maintaining a healthy diet) than mainland Japanese citizens. Their restricted diet was associated with a 60 to 70 percent reduction in incidence of deaths due to cancer and cardiovascular disease. Recent generations of Okinawans no longer show these health and longevity advantages (Gavrilova & Gavrilov, 2012 ). The reason, some researchers speculate, is the introduction of Westernized food, including fast food, to Okinawa.

Similarly, normal-weight and overweight people who have engaged in self-imposed calorie restriction for 1 to 12 years display health benefits—reduced blood glucose, cholesterol, and blood pressure and a stronger immune-system response than individuals eating a typical Western diet (Fontana et al., 2004 , 2010 ; Redman et al., 2008 ). Furthermore, in the first experiment involving random assignment of human participants to calorie-restricted and nonrestricted conditions, the restricted group again displayed improved cardiovascular and other health indicators, suggesting reduced risk of agerelated disease (Redman & Ravussin, 2011 ).