Epidemiology: The Growing Number of Older Adults

The world is experiencing a remarkable shift in its population structure. Today, people worldwide are living longer than ever before, with most expecting to live into their sixties and beyond. This change is not happening in just one country or region—every nation is witnessing growth in both the size and proportion of older persons in the population.^[1]

By 2030, one in six people in the world will be aged 60 years or over. At that time, the share of the population aged 60 years and over will increase from 1 billion in 2020 to 1.4 billion. Looking further ahead to 2050, the world’s population of people aged 60 years and older will double to 2.1 billion. Even more striking, the number of persons aged 80 years or older is expected to triple between 2020 and 2050, reaching 426 million.^[1]

In the United States specifically, the demographic picture is equally dramatic. Individuals over the age of 65 accounted for about 17 percent of the total population in 2022, representing just over 58 million Americans. By 2030, all Baby Boomers will be age 65 or older, and by 2040, roughly 78.3 million Americans will fall within that age group—representing 22 percent of the American population.^[2] Traditional definitions consider people to be “elderly” or “older adults” starting at age 65, though this designation was originally based on historical retirement ages in Germany rather than biological factors.^[3]

This shift in population distribution toward older ages—known as population ageing—started in high-income countries. For example, in Japan, 30 percent of the population is already over 60 years old. However, it is now low- and middle-income countries that are experiencing the greatest change. By 2050, 80 percent of older people will be living in low- and middle-income countries, and the pace of population ageing in these regions is much faster than it was in the past.^[1]

Among the elderly population, women outnumber men significantly, especially at older ages. In 1986, for every 100 males under age 20, there were 96 females. However, for persons over age 65, the ratio was almost 1 to 1.5, and for those 85 and older, the ratio reached 1 to 2.5, highlighting the numerical predominance of women over men in these older age ranges.^[9]

Causes: Understanding the Aging Process

Aging is a gradual, continuous process of natural change that begins surprisingly early—in early adulthood. During early middle age, many bodily functions begin to gradually decline. At the biological level, aging results from the accumulation of a wide variety of molecular and cellular damage over time. This damage builds up slowly and is the result of normal wear and tear on the body’s systems.^[1]

These biological changes lead to a gradual decrease in physical and mental capacity, a growing risk of disease, and ultimately death. The changes are neither linear nor consistent, meaning they don’t happen at the same pace for everyone or follow a predictable pattern. They are only loosely associated with a person’s age in years. This explains why some people seem biologically younger than others of the same chronological age.^[1]

The diversity seen in older age is not random. Most noticeable differences in apparent age among people of similar chronologic age—which is simply a person’s age in years—are caused by lifestyle, habits, and subtle effects of disease rather than by differences in actual aging. Some people are biologically older at 65, while others may not reach this stage until a decade or more later.^[3]

Beyond biological changes, aging is often associated with other life transitions. These can include retirement, relocation to more appropriate housing, and the death of friends and partners. These social and psychological factors interact with biological aging to create the full experience of growing older.^[1]

Risk Factors: What Increases the Challenges of Aging

While aging itself is universal, certain factors can increase the likelihood of experiencing problems during the later years of life. Understanding these risk factors helps individuals and families prepare and potentially reduce some of the difficulties associated with aging.

Lower income represents a significant risk factor for poor health outcomes in older adults. Older adults with lower incomes are more likely to have disabilities and die younger. Disability is likely to start earlier in life for people with lower incomes, further raising the risk of early mortality.^[16] Nearly one in ten older adults in the United States lives in poverty, which can limit access to nutritious food, adequate housing, and healthcare.^[16]

Social isolation and loneliness are increasingly recognized as serious risk factors for older adults. Although they sound similar, they are different: social isolation is the lack of social contacts and having few people to interact with regularly, while loneliness is the distressing feeling of being alone or separated. Both are associated with higher risks for health problems, such as depression, heart disease, and cognitive decline—which is a decrease in the ability to think, learn, and remember.^[17]

Decreased mobility becomes more common with age, which can increase the risk of falls. Falls are a leading cause of injury for older adults, with one in four older adults falling each year. Falls can result in serious injuries, including fractures and head trauma, and can lead to a loss of independence.^[7]

Living in rural areas or areas with limited healthcare access poses additional risks. These factors can make it harder for older adults to receive regular medical care, access medications, and get help during emergencies. The built environment—including the accessibility of neighborhoods, convenient access to grocery stores, and safe places to be active—becomes increasingly important as mobility decreases with age.^[16]

Symptoms: Changes Associated with Getting Older

As people age, they may notice various changes in their bodies and abilities. It’s important to understand which changes are a normal part of aging and which might signal a health problem that needs attention. The distinction between normal aging and disease is not always clear, which can lead to confusion and concern.^[3]

Common conditions in older age include hearing loss, cataracts and refractive errors, back and neck pain, and osteoarthritis—which is the wearing down of the protective cartilage in joints. Other frequent conditions include chronic obstructive pulmonary disease (a lung condition that makes breathing difficult), diabetes, depression, and dementia. As people age, they are more likely to experience several conditions at the same time, a situation called multimorbidity.^[1]

With advanced age, a mild decline in mental function is nearly universal and is considered normal aging. This decline includes increased difficulty learning new things such as languages, decreased attention span, and increased forgetfulness. People who are aging normally may misplace things or forget details. In contrast, the decline that occurs in dementia is much more severe—people with dementia forget entire events, have difficulty doing normal daily tasks like driving or cooking, and struggle to understand their environment, including knowing what year it is or where they are.^[3]

Physical changes are also common. The heart and blood vessels undergo changes over time. Arteries commonly become stiffer, causing the heart to work harder to pump blood through these vessels. The heart muscles change to adjust to the greater workload. While the heart rate at rest likely stays about the same, it won’t rise during activities as much as it used to. These changes raise the risk of high blood pressure and other conditions related to the heart and blood vessels.^[6]

Vision changes typically occur with aging. The lens of the eye thickens, stiffens, and becomes less able to focus on close objects such as reading materials—a condition called presbyopia. This change occurs in virtually all older adults and is considered normal aging.^[3]

Older adults often face social problems related to retirement, loneliness, and ageism—which is discrimination or negative attitudes based on a person’s age. Depression is particularly common in seniors and can be caused by the loss of their child-caring role, loss of daily career duties through retirement, a move from a house to a retirement community, chronic illness or pain, death of a spouse or close friends, loss of independence, or certain medications. Depression is a serious, debilitating disorder that is not a natural part of aging.^[19]

Prevention: Steps to Promote Healthy Aging

Although aging is inevitable, many of the challenges associated with growing older can be prevented or delayed through healthy lifestyle choices and proactive healthcare. It’s never too late to start healthy habits, and adopting these behaviors can help older adults live longer, healthier lives and maintain independence.^[17]

Physical activity stands out as one of the most important preventive measures. Moving more can help older adults manage their health, live as independently as possible, and maintain quality of life. In general, the goal is to get at least 150 minutes of physical activity each week. This can include brisk walking, swimming, dancing, or other activities that people enjoy. Regular physical activity can help maintain a healthy weight, lower heart disease risk, prevent chronic diseases, and slow or even improve physical incapacity. It also helps maintain mobility, strength, and overall health.^[6]

Eating a healthy diet is equally crucial. Older adults should choose vegetables, fruits, whole grains, high-fiber foods, and lean sources of protein such as fish. Fruits and vegetables are especially beneficial, and experts recommend aiming for five total servings a day—for example, three servings of vegetables and two servings of fruit. It’s also important to limit foods that are high in unhealthy fats, salt, and added sugars. Good nutrition is crucial for overall well-being at every life stage, though as people age, they typically require fewer calories but may need increased amounts of certain nutrients.^[6]

Preventing social isolation and loneliness is another key aspect of healthy aging. Staying socially connected can help older adults avoid the health problems associated with isolation, such as depression, heart disease, and cognitive decline. Family members can play an important role by scheduling regular phone calls or video chats, encouraging older loved ones to seek out others with similar interests, helping them find local activities or volunteer opportunities, and ensuring they have reliable transportation to social events.^[17]

Regular medical check-ups are essential for monitoring health and detecting potential issues early. Routine screenings, vaccinations (including flu and pneumonia vaccines), and specialty consultations help ensure comprehensive care. Older adults are more likely to go to the hospital for some infectious diseases, including pneumonia, which is a leading cause of death for this age group. Making sure older adults get preventive care can help them stay healthy.^[1]

Mental well-being should not be overlooked. Keeping the brain sharp by learning new skills or hobbies—such as trying puzzles, reading, doing crafts, learning a new language, or taking online courses—stimulates cognitive abilities. Continuous learning keeps the mind sharp and can be incredibly fulfilling. Managing stress through healthy coping mechanisms, such as journaling, walking, meditation, or tai chi, is also important for overall health.^[23]

Getting adequate sleep is another preventive measure. Aiming for seven to nine hours of quality sleep each night supports both physical and mental health. Although sleep issues like insomnia become more common with aging, consulting a physician can help identify solutions and underlying issues.^[23]

Pathophysiology: How the Body Changes During Aging

Understanding the physical and biochemical changes that occur in the body as people age helps explain why certain health issues become more common and why the body responds differently to illness and treatment. These changes affect virtually every system in the body and occur gradually over many years.

At the cardiovascular level, the heart and blood vessels undergo significant changes. As mentioned earlier, arteries commonly become stiffer over time due to changes in the vessel walls. This arterial stiffness means the heart must work harder to pump blood through these less flexible vessels. The heart muscle itself changes in response to this increased workload, sometimes becoming thicker. The heart rate at rest typically remains stable, but the heart’s ability to increase its rate during physical activity or stress diminishes. These changes increase the risk of high blood pressure and other cardiovascular conditions.^[6]

The musculoskeletal system also experiences notable changes. Bone density tends to decrease with age, particularly after menopause in women, increasing the risk of osteoporosis—a condition where bones become weak and brittle, making fractures more likely. Muscles may lose mass and strength, a condition called sarcopenia. Joint cartilage can wear down, leading to osteoarthritis, which causes pain and stiffness. These changes can affect mobility and increase the risk of falls and injuries.^[7]

In the sensory systems, vision and hearing commonly decline. As noted, the lens of the eye becomes less flexible, affecting the ability to focus on nearby objects. Other age-related eye changes can lead to cataracts or other vision problems. Hearing loss often begins gradually and can affect the ability to hear high-frequency sounds or understand speech in noisy environments.^[1]

The nervous system undergoes changes that affect cognitive function and coordination. While severe cognitive decline is not a normal part of aging, some changes do occur. These include slower information processing, decreased attention span, and some memory changes. The accumulation of cellular damage in the brain over time contributes to these changes. The brain’s ability to produce certain neurotransmitters—chemical messengers that allow brain cells to communicate—may also decline.^[1]

The immune system typically becomes less effective with age, a phenomenon sometimes called immunosenescence. This makes older adults more susceptible to infections and may reduce the effectiveness of vaccines. The body’s ability to recognize and fight off pathogens decreases, and the inflammatory response may become dysregulated, contributing to chronic low-level inflammation that is associated with many age-related diseases.^[14]

Metabolic changes also occur, affecting how the body processes nutrients and medications. Kidney function often declines with age, which can affect how drugs are cleared from the body. Liver function may also change, influencing drug metabolism. These changes mean that older adults may need different medication doses than younger people and are at higher risk for drug interactions and side effects.^[14]

The digestive system experiences changes that can affect nutrition and comfort. The production of saliva and digestive enzymes may decrease, affecting digestion. Motility—the movement of food through the digestive tract—can slow down, potentially leading to constipation. Changes in taste and smell can reduce appetite and enjoyment of food, potentially leading to nutritional deficiencies.^[6]

Skin undergoes visible changes, becoming thinner, less elastic, and more fragile. The skin’s ability to sense pressure and temperature may diminish, increasing the risk of injuries. Wound healing typically slows with age due to changes in circulation and cellular repair mechanisms. These changes make older adults more vulnerable to skin injuries, pressure ulcers, and infections.^[14]

Despite these changes, it’s important to recognize that the extent and pace of these physiological changes vary greatly among individuals. Many changes can be slowed or partially reversed through healthy lifestyle choices, including regular exercise, good nutrition, adequate sleep, stress management, and staying socially and mentally engaged. The body retains remarkable capacity for adaptation and recovery, even in advanced age.^[17]