Development in the middle and later years of adulthood is best conceived of within the biopsychosocial model (Whitbourne & Whitbourne, 2020), which describes the intersecting influence of multiple forces reflecting changes occurring within the individual in the context of sociohistorical factors. Biological changes include those due to primary aging that take place in the form of physical changes affecting bodily appearance, major organ systems, and the nervous system. Across the decades of adulthood, individuals become more likely to develop chronic illnesses, a process known as secondary aging. Changes in physical functioning and health interact with psychological changes in such areas as cognition, personality, and emotions. Sociocultural effects further influence the individual’s psychological development through such mechanisms as income inequality, access to healthcare systems, and lifelong patterns of occupational and educational status. Furthermore, aging takes place against the cultural backdrop of ageism, the stereotyping of and discrimination against individuals on the basis of age.

Major age-related changes in the body in adulthood and later life include alterations in the appearance and structure of the skin, which undergoes thinning of the dermal layer and changes in coloration (Farage et al., 2013). These intrinsic processes are accelerated by photoaging, or exposure to the ultraviolet rays of the sun (Maddodi et al., 2012). Increases in body mass index reflect changes in metabolism related to alterations in the endocrine system, but also are a function of the social determinants of health, such as income and occupational status (Amies-Cull et al., 2022). Sarcopenia, the gradual loss of muscle mass (Rong et al., 2020), combines with osteopenia, the reduction in bone mineral content (Demontiero et al., 2012), and normal age-related changes in the joints due to thinning of cartilage and bony spur outgrowths to lead to changes in the individual’s mobility (Teichtahl et al., 2009). Fear of falling can accentuate these challenges to safely navigating the environment on the part of the older person (Cruz-Jimenez, 2017).

The accumulation of plaque in the arteries, both as a result of normal aging and the disease of atherosclerosis, results in a reduction of the ability of the heart to pump blood to the cells of the body, leading to declines in aerobic capacity. Changes in the structures that support the functioning of the lungs, bladder, along with altered immune and endocrine function play important roles in affecting the body’s adaptive abilities. Each of these systems are also potential targets of secondary aging, the accumulation of risk with increasing age in adulthood. The major chronic diseases include cardiovascular disease, kidney disease, cancer, chronic obstructive pulmonary disorder, and disturbances in sleep and susceptibility to infection. Tooth loss and gum disease, reflecting both intrinsic age-related changes and hygiene, can further alter the individual’s adaptation during the later years of adulthood (Whitbourne, 2022). Lifestyle habits, including diet, exercise, alcohol intake, and smoking can all alter the course of primary aging as well as the development of chronic diseases (National Center for Chronic Disease Prevention and Health Promotion, 2022).

Changes in the nervous system due to normal aging occur progressively throughout adulthood, but even loss of hippocampal volume, important in learning and memory, can be compensated for by active lifestyle involvement, particularly physical exercise (Fraser et al., 2022) as well as engagement in cognitively-challenging activities (Belchior et al., 2019; Pauwels et al., 2018). Several models exist that propose a variety of routes for compensation, or plasticity, within the brain, as well as the beneficial effect of brain reserve, or untapped resources (Cabeza et al., 2018).

Sensory structures change with age and can result in altered vision through presbyopia (loss of near vision), and presbycusis (age-related hearing loss). Additionally, the majority of older adults develop cataracts, or clouding of the lens; other significant sources of vision loss include macular degeneration and glaucoma. Other than protection through avoidance of noise exposure, these sensory changes are not preventable, but most are treatable. These sensory changes are important to consider when interacting with older adults, especially with respect to communication strategies, such as reducing background noise and maintaining direct eye contact during a conversation (Janse, 2009).

Psychologically, attention and working memory are the cognitive systems that experience the most significant age-related changes, but can also be compensated through plasticity (Froudist-Walsh et al., 2018). Although some executive functions show age-related losses, other abilities are maintained or improved, including inhibitory efficiency (Veríssimo et al., 2022). Additionally, neurocognitive disorders occur in a minority of older adults, and the associated changes in cognition, personality, and everyday functioning have a significant impact on those who experience them as well as their caregivers and family members (Novais et al., 2018).

Research on aging and intelligence shows that such abilities as semantic memory and factual knowledge can be maintained into the 70s and beyond, particularly for individuals who remain engaged in diverse leisure and social activities (Luo et al., 2023). Considerable evidence suggests that lifestyle and sociocultural factors play an important role in the continued maintenance of cognitive aging (Anatürk et al., 2021).

Contradicting long-held assumptions that personality remains stable after early adulthood, a growing body of evidence provides support for changes both in personality traits, as reflected in the Five Factor Model (Bleidorn et al., 2022), and psychosocial qualities, consistent with Erikson’s theory (Mitchell et al., 2021). Additionally, cognitive and personality changes interact (Ziegler et al., 2018), such that individuals higher in personality traits such as openness to experience both seek, and are affected by, exposure to new ideas and opportunities for intellectual growth.

Sociocultural factors interact substantially with physical and psychological changes. As noted earlier, these factors can impact health, but in the larger context, ageism has significant effects on the well-being of older adults. The majority of older adults are exposed to “everyday ageism” (National Poll on Healthy Aging, 2020), which can take its toll on physical and mental health. Gender, sexual orientation, race and ethnicity also interact with ageism, placing older adults in a status of “multiple jeopardy,” or intersecting identities (American Psychological Association, 2020). Intergenerational family relationships and community (Carr, 2023), however, provide vital sources of support for older individuals (Li et al., 2019).

Despite the challenges that they encounter, current cohorts of older adults have lower rates of psychological disorder, including depressive, anxiety, addictive, and personality disorders (Whitbourne & Meeks, 2010). Models of resilience (Carr, 2023) and successful aging (Plugge, 2021) point to the potential for continued growth in feelings of life satisfaction, subjective happiness, and social engagement despite objectively-measured changes in health and cognitive functioning. People in later life appear not only to manage to feel satisfied with their lives but also to be able to achieve new forms of creative expression, productivity, and vital involvement.

Written by Susan Krauss Whitbourne, PhD, ABPP, University of Massachusetts Boston