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Learning Objectives

By the end of this section, you will be able to:

• Describe the difference between primary and secondary aging
• Identify changes in perception, memory, and information processing during middle adulthood
• Identify key changes in sensory abilities across middle adulthood
• Describe physical changes to the body across middle adulthood

At forty-six years old, quarterback Tom Brady announced his retirement after spending over twenty years as a top player in the NFL. He retired as the number one quarterback in NFL history, but what is perhaps most amazing about his career is how he continued to develop physically after entering middle adulthood. Tom Brady won four of his seven Super Bowl Championships and three of his five Super Bowl MVP awards after thirty years of age, and actually became a faster athlete in certain measures. Tom credits a healthy daily diet and exercise routine with maintaining physical ability, mental sharpness, and energy well into middle adulthood. Even in retirement, he enjoys many activities like working out with friends and riding bikes with his children. He is also involved with community service organizations that help those in need, including the Make-A-Wish Foundation, the Boys & Girls Clubs of America, and Best Buddies International. Whereas Tom’s physical achievements are by no means typical for his age, his dedication to work, family, personal wellness, and community service is an exceptional example of the developmental benefits of active engagement in middle adulthood (DeArdo, 2024; Patra, 2023; Petre & Knott, 2022).

Physical and cognitive changes in middle adulthood tend to be gradual, occurring over many years. The nearly thirty-year length of this life stage allows for a wide variety of developmental experiences, both within and between individuals. For example, some adults begin to show gray hair in their thirties, while others don’t gray during this stage. These variations make it difficult to generalize about physical development in middle adulthood. Variation in human aging is largely explained by the interaction of our genetics with our experiences. Aging from inevitable and genetically influenced biological changes is known as primary aging. For example, with age, hair follicles naturally reduce their production of pigment, which results in graying hair. On the other hand, secondary aging results from the influence of environmental or behavioral factors, as opposed to genetic influences. For example, many signs of aging skin, such as wrinkles and changes in pigmentation, are caused by sun exposure.

Physical aging is an inevitable part of the human life cycle. The timing and experience of the related processes are improved for many adults by increasing healthy behaviors and having a positive mindset. Adults generally often adopt healthier eating behaviors with age (Whitehead, 2016), are less likely to experience mental illness (NIMH, 2021) during the period of middle adulthood compared to other periods of the lifespan. Individuals in middle adulthood also often develop more positive perceptions of aging by prioritizing their emotional and psychological goals (Carstensen & Mikels, 2005).

Changes in the Brain

Although the human brain does not physically grow in adulthood, its functions—like perception, memory, and information processing—continue to evolve. Some aspects stabilize and are indistinguishable from those of early adulthood, such as the ability to make and utilize mental images (Caçola et al., 2013). Researchers have also identified changes in other areas of the brain during middle adulthood, some of which show improved functioning and some of which show decreased functioning.

Perception

The brain perceives and responds to emotional stimuli differently in middle adulthood. Findings suggest that compared to younger adults, middle-aged adults pay more attention to and recall positive stimuli, like a smiling infant or cute kittens, and show less amygdala reactivity (recall that the amygdala is the part of the brain that produces automatic fear and anger responses) when exposed to negative images, like a snarling dog or a gruesome injury (Charles et al., 2003; Mather et al., 2004) (Figure 13.2). This shift in attention to and processing of positive versus negative emotional information is called the positivity effect and may help promote psychological and emotional well-being (Carstensen, 2021; Carstensen & Reynolds, 2023). The positivity effect may also boost physical health, since positive affect has been found to predict healthy exercise behaviors in adulthood (Whitehead, 2016).

Figure 13.2 When shown an array of photos that depict emotionally positive, neutral, and negative images, middle-aged adults pay more attention to positive images, such as (a) a cute kitten. They exhibit less amygdala reactivity as compared to young adults when shown negative images, such as (b) a snarling dog. (credit a: modification of work “Tabby cat with blue eyes” by Adina Voicu/Wikimedia Commons, CC0 1.0; credit b: modification of work “angry dog” by Stebunik/Wikimedia Commons, CC BY 3.0)

Memory and Information Processing

It is not uncommon to hear adults in middle age comment about becoming forgetful and even seeking out memory assessments. This perceived memory loss is not supported by research, however. No differences in memory are typically found between middle and young adults, and people in these developmental stages seem to generally function at the same level in terms of memory (Salthouse, 2012). It is more likely that perceived forgetfulness is a result of the cognitive overload associated with the responsibilities of parenting, looking after aging parents, maintaining a career, and so on (Mayo Clinic Health System, 2022).

One real change in brain processes in middle adulthood is a slower processing speed than at younger ages. Scientists gauge processing speed by measuring reaction time, such as how quickly a person presses a button on a keyboard when prompted. Adults also have more difficulty filtering distracting stimuli during a task (Kray et al., 2008) (Figure 13.3). In the brains of middle-aged adults, more areas of the cortex are activated in response to cognitive tasks than in younger adult brains (Gunter et al., 1998; Kwon et al., 2016). One explanation might be that ideas are being associated with greater memory context in older adults because of their life experience. For example, when shown random images as part of a memory task, middle-aged adults with more life experience might associate those random images with a broader network of personal memories than would a young adult. While this broader network activation may slow processing speed, it also likely enables more complex and nuanced problem-solving abilities. However, reduced processing speed may also be exacerbated by long-term health problems, such as diabetes (Tufvesson et al., 2013) or chronic pain (Rouch et al., 2021).

Figure 13.3 Middle-aged adults have more difficulty filtering distracting stimuli during a task, such as interruptions while working. (credit: modification of work “Man playing with dog” by Nehemiah Brent/nappy, Public Domain)

Brain Health

As general health concerns increase in midlife, many people wonder how to maintain brain health and prevent cognitive decline, dementia, or illnesses like Alzheimer’s disease. Researchers have investigated the connection between brain health and various lifestyle factors, including diet, dental hygiene, exercise, and social engagement.

Some reports suggest moderate amounts of caffeine (two to three cups of coffee a day) are associated with lower risks of developing dementia (Zhang et al., 2021). However, high rates of caffeine consumption have been associated with increased rates of dementia and reduced hippocampal volume (Pham et al., 2021).

Potential benefits or risks of alcohol consumption vary: Moderate amounts (one to two drinks a day) may reduce dementia risk, whereas large amounts are associated with increased risk compared to nondrinking (Jeon et al., 2023). Recommendations about alcohol are complicated by the difficulty in pinpointing the exact level at which consumption becomes dangerous. As a result of this uncertainty, the World Health Organization (WHO) has published a statement that no level of alcohol consumption is deemed safe (WHO, 2023), as there is not a clear upper limit for healthy alcohol consumption.

The Mediterranean diet—high in fruit, vegetables, grains, and olive oil and low in red meat and processed foods—has also been associated with protecting healthy brain functioning. In particular, the brains of adults following this eating approach are less likely to exhibit the accumulation of plaques in the brain that lead to cognitive decline and Alzheimer’s disease (Agarwal et al., 2023).

Link to Learning

Many aspects of the Mediterranean diet can be more affordable than less healthy food choices. For example, protein sources such as lentils and chickpeas are often cheaper than meat-based proteins. However, other food choices may be more costly, such as using olive oil instead of other sources of fat. Check out this article about more affordable ways to eat the Mediterranean way to learn what to prioritize on your shopping list.

Researchers have investigated the connection between oral health and dementia risk. A study of more than 6,000 patient medical records revealed that adults with periodontal disease were more likely to be later diagnosed with dementia (Beydoun et al., 2020). Postmortem analyses of the brains of deceased individuals with dementia found higher levels of a type of bacteria associated with gingivitis. These bacteria can release an enzyme that damages nerve cells and causes symptoms of dementia and Alzheimer’s disease. Although these results are correlational rather than causal, researchers are examining how proactive oral care and treatments for bacterial infections in the mouth may reduce the risk of dementia (Dominy et al., 2019).

Staying or becoming physically active also benefits brain health. Cardiovascular exercise increases blood flow, which promotes the growth of capillary and neural networks in the brain (Konopka, 2015). Physical exercise has been associated with better cognitive function in both naturalistic and experimental settings. Older adults who exercise regularly perform better on tests of cognitive function than those who do not, even when controlling for other health and lifestyle factors (Kumar et al., 2022). Following a stroke, adults who participated in a thorough and progressive fitness program involving strength and aerobic exercises showed greater cognitive performance at a six-month follow-up than did those in low-intensity fitness programs (Liu-Ambrose et al., 2022).

Cohen (2004) proposes that strong social ties may deliver both direct and indirect benefits to adults’ health. Social ties buffer against stress, and chronic stress has been found to cause changes in brain chemistry that eventually shrink structures of the brain involved in cognition, such as the hippocampus (Willner, 2017). Social participation may also encourage engagement in activities that promote brain and cognitive health, including physical and intellectual activity (Cohen, 2004).

Changes in Sensory Abilities

In addition to experiencing changes to how the brain perceives and processes information, people may notice changes in their sensory abilities during middle adulthood. Structural components of the eyes change, hearing acuity declines, and there are subtle changes to the sense of touch.

The eyes experience a loss of visual acuity in middle age, which is referred to as presbyopia. Two common issues arise: First, a thickening of the eye’s lens reduces its elasticity, making it less likely to bend to accommodate targets closer to the eye. As a result, middle-aged adults often have trouble seeing up close and experience blurriness when reading, as shown in Figure 13.4. A second aspect of presbyopia is the buildup of yellowish extracellular debris that can cause age-related macular degeneration (AMD), a deterioration of the light receptors in the retina (Grossniklaus et al., 2013).

Figure 13.4 The lens that bends and flattens to focus light entering the eye becomes less flexible in middle adulthood, making it more difficult for the eye to focus on objects near to the face. As a result, middle-aged adults might experience blurriness when reading small text without reading glasses. (credit left and right: “nutrition facts” by Carol Clarkson/Flickr, CC BY 4.0; credit middle: modification of work “Eye Anatomy” by BruceBlaus, Medical gallery of Blausen Medical 2014/Wikimedia Commons, CC BY 3.0)

Difficulty adjusting to changes in light may also cause challenges for night driving. In middle age, the pupil does not dilate or constrict as much in response to bright or dimly lit conditions. Compared to younger adults, drivers in middle adulthood self-report greater difficulty seeing pedestrians at night compared to daytime (Mikoski et al., 2019).

Age-related hearing loss is called presbycusis. Over time, the inner ear’s structures and nerves slowly deteriorate, and initial hearing loss first affects adults’ ability to detect high-frequency sound waves. As a result, they may notice an increasing difficulty in hearing high-pitched noises, such as a beeping microwave or dinging cell phone or doorbell. Hearing loss is also exacerbated by cigarette smoking, high blood pressure, and diabetes (Baiduc et al., 2023). Hearing loss due to chronic noise exposure is estimated to affect as many as 25 percent of U.S. adults (National Institute on Deafness and Other Communication Disorders, 2022), particularly men who are traditionally more likely to work in professions with high-volume noise, such as construction or mining (Hoffman et al., 2017). For example, the second most common disability benefit for U.S. service members (a group where men outnumber women at least four to one) is for hearing loss, with 1.3 million people receiving compensation (Veteran Benefit Administration, 2020).

Link to Learning

Explore this audiovisual representation of different frequency levels within the human audio spectrum to learn what they sound like. What sounds do you encounter in daily life that might be at low frequency? Medium frequency? High frequency?

Among veterans receiving disability benefits, hearing loss is topped only by tinnitus, another hearing-related condition caused by exposure to loud noises, which causes the sensation of persistent ringing in the ear (U.S. Department of Veterans Affairs, n.d.). Hearing aids can be beneficial to those experiencing hearing loss; however, only 16 percent of those who need them use them. The National Council on Aging identified barriers to hearing aid use, including access to and cost of health care in the United States (Everett, 2023). As a result, many adults consider treatment of hearing loss to be a lower priority than other health-care needs. However, supportive health care for hearing loss is crucial to keeping the growing adult population engaged and healthy. Chronic hearing loss can impede work, social engagement, and daily activities. Straining to hear while working, socializing, or accomplishing daily tasks can lead to stress, fatigue, and impaired brain function. Those who do acquire hearing aids are, therefore, less susceptible to cognitive decline and even dementia risk (Yeo et al., 2022).

Other sensory capabilities may also decline in middle age. As skin thins and loses elasticity with age, sensitivity to hot and cold decreases (Huang et al., 2010). In middle adulthood, proprioception, the body’s sense of location and movement in space, also becomes less acute, making adults more prone to loss of balance, falls, and ankle injuries as they age (Pinto et al., 2020).

Link to Learning

Noise-induced hearing loss (NIHL) is a major cause of secondary aging. The National Institute on Deafness and Other Communication Disorders (NIDCD) identifies common sources of unhealthy noise exposure you might encounter throughout life and ways to prevent NIHL. The NIDCD websites present health information about NIHL and a NIDCD Fact Sheet on NIHL that presents further details.

Body Changes

In midlife, adults begin to experience changes to their bodies. These changes may initially be more apparent in external visible areas like the skin. In contrast, internal changes, such as reduced bone density, may not be readily noticed.

Body Composition

Body composition changes can often be the most apparent signs of aging. Over time, the middle-aged body loses muscle and adds body fat. Age-related muscle loss is called sarcopenia. After the age of fifty years, adults lose 1 to 2 percent of muscle each year (Larsson et al., 2019; Marcell, 2003). Related to both sarcopenia and the increase in body fat is also an increase in obesity among middle-aged adults, which is associated with numerous health issues. Slowing metabolism is commonly associated with weight changes in middle age, and it does bear some of the responsibility. The chemical process by which bodies convert food to energy is metabolism. In middle adulthood, the basic metabolic rate declines, meaning the body now needs less energy when at rest (Pontzer et al., 2021).

Typical middle-aged bodies for women are not well represented in the media. A recent season of The Golden Bachelor, which focused on older adults’ search for love, received criticism for the lack of body diversity among the contestants (Battle, 2023). And while adults increasingly focus on how their bodies function (as opposed to how they look) (Roy & Payette, 2012), exposure to images of idealistically thin bodies has been found to negatively influence body image, regardless of age (Price et al., 2023), especially for White women (Roy & Payette, 2012). On the other hand, adults with more positive attitudes toward aging and higher self-esteem are more likely to report positive body image (Pearce et al., 2014; Price et al., 2023).

Semaglutide hormone therapies are being explored as medical approaches to weight management, particularly for adults at risk for diabetes and cardiovascular disease. Semaglutide acts on the hypothalamus to reduce appetite and food intake, and initial studies have found promising results for patients using these injectable medications to sustain weight loss and lower risk of cardiovascular disease and diabetes (Lincoff et al., 2023; Ryan et al., 2024; Wadden et al., 2021).While drugs that contain semaglutide, such as Ozempic and Wegovy, were originally developed to treat type 2 diabetes, researchers are exploring their usefulness for weight management. While Wegovy is approved by the U.S. Food and Drug Administration (FDA) as a method of weight management, Ozempic is still only FDA approved to treat type 2 diabetes and lower the risk of associated cardiovascular disease (FDA, 2024). More research is needed to determine the long-term effectiveness against possible side effects and risks of these drugs as medical approaches to adult weight management.

Skin

The skin shows noticeable signs of aging, such as wrinkles, age spots, and sagging. The layers of skin lose their elasticity, thickness, and water and fat content, which causes the skin to appear loose or wrinkled. Too much sun exposure without adequate protection (e.g., using sunscreen or wearing a hat) results in secondary aging with sunspots, wrinkling, and increased risk of skin cancer (Wong & Chew, 2021) (Figure 13.5).

Figure 13.5 Regular use of sun protection, such as (a) sunscreen and (b) hats, can reduce the effects of secondary aging, such as wrinkles and sunspots. (credit a: modification of work “Pregnant woman standing outdoors, while applying sunscreen to her exposed skin (21755)” by Lauren Bishop/Centers for Disease Control and Prevention, Public Domain; credit b: modification of work “Keenan Adams models the new uniform sun hat!” by U.S. Fish and Wildlife Service Southeast Region/Wikimedia Commons, Public Domain)

Bone Density

One important health concern in middle adulthood is decreasing bone density. Bone density reaches a peak in the mid to late thirties and then progressively declines in a process called osteoporosis. Osteoporosis, which can result in more frequent bone fractures and breaks, occurs in those assigned female at birth (AFAB) at twice the rate as it does for those assigned male at birth (AMAB), owing to the reduction of estrogen and progesterone experience during menopause. The risk of osteoporosis can be reduced through diet and exercise.

Increasing calcium consumption starting in early adulthood helps the body to grow and helps strengthen the bones and teeth. However, the body does not produce its own calcium, so this nutrient must be obtained through calcium-rich foods, such as dairy products, almonds, dark leafy greens, salmon, and tofu. Vitamin D helps the body to absorb the calcium in these foods. Vitamin D is produced naturally by the body but can also be supplemented by foods rich in vitamin D, such as fish, eggs, mushrooms, and vitamin D–fortified foods, such as milk and cereal.

Bone health can also be promoted through regular participation in strength-training exercises, which have been shown to increase bone density in persons AFAB (Kistler-Fischbacher et al., 2021; Nelson et al., 1994). Strength training also helps support balance, metabolism, and cognition (Mayo Clinic, 2023). Strength training does not require weightlifting but rather weight-bearing exercises. Weight-bearing exercises are those that require the bones and joints of our body to sustain our own body weight and can include yoga, walking, jogging, or climbing stairs (Figure 13.6).

Figure 13.6 Our bodies adapt to weight-bearing exercises, such as planks and climbing stairs, by increasing bone density, which promotes bone strength. (credit: Woman doing push ups” by David Stewart/https://homegets.com, CC BY 2.0)

It Depends

Do Professional Athletes Have to Retire before Middle Adulthood?

You earlier read the story of athlete Tom Brady, who retired from professional football at forty-six years of age. While in most major professional sports, athletes retire before age thirty (RBC Wealth Management, 2024), some notable individuals continue achieving in their thirties, forties, and even fifties. Serena Williams won the 2017 Australian Open at the age of thirty-five years, while eight weeks pregnant. The oldest woman athlete at the 2022 Winter Olympics was Germany’s Claudia Pechstein, a speed skater who placed ninth just three days before her fiftieth birthday. Japanese soccer player Kazuyoshi Miura plays for Yokohama FC at the age of fifty-seven years.

While these individuals are all notable, several subtle changes occur physically that can make continued athletic achievements like these difficult after early adulthood. Reaction times in middle adulthood are slower than in young adulthood. Changes of even 0.1 milliseconds can be enough to affect performance in many reactionary or responsive sports (like reacting to a serve in tennis). The changes in metabolism and body composition require adjustments to training and diet to maintain a fitness level appropriate for competing with athletes who are at their optimal younger age. Athletes who continue playing in middle age maintain careful diets and engage in increased strength work to maintain muscle and bone mass.