This chapter reviews biodemographic theories of aging that attempt to answer the proverbial ‘why’ and ‘how’ questions in gerontology. Biodemography of aging represents an area of research that integrates demographic and biological theory and methods and provides innovative tools for studies of aging and longevity. The historical development of the biodemography of aging is closely interwoven with the historical development of statistics, demography, and even the technical aspects of life insurance. The chapter also reviews some applications of reliability theory to the problem of biological aging. Reliability theory of aging provides theoretical arguments explaining the importance of early-life conditions in later-life health outcomes. Moreover, reliability theory helps evolutionary theories explain how the age of onset of diseases caused by deleterious mutations could be postponed to later ages during the evolution this could be easily achieved by simple increase in the initial redundancy levels.

This chapter describes the interpretive perspective in all its richness and variability in guiding research and advancing understanding of a wide range of phenomena in aging and life-course research. It discusses the interpretive perspective with other variants of social science theorizing, particularly normative perspectives on aging and life course-placing its development in historical context. The chapter addresses the contentious issue of causal explanation, as understood in diverse disciplinary contexts. It highlights some prominent normative theoretical approaches in social gerontology, by way of providing a comparative context for our primary consideration of the interpretive perspective. A given theoretical perspective in gerontology can focus solely on macro level, structural phenomena, on micro-level behavior and social interaction, or on understanding of the links between macro and micro phenomena.

This chapter traces the development of concepts and theories in the sociology of aging from the 1940s through the mid-1970s through seven themes. The first theme describes the importance of age in social structure and the place of the aged in changing societies. The second theme focuses on the issue of ‘successful aging’: how to define, measure, and achieve it. The third theme highlights the tension between social structure and individual agency in the activity versus disengagement theory controversy. The fourth theme concerns the social meanings of age, age cohorts, and generations, as well as interactions between age groups. The fifth theme focuses on families, aging, and intergenerational relations. The sixth theme of age stratification deals with the interplay between cohort succession and the aging of individuals. The seventh theme addresses the life course as a socially constructed process.

There can be little doubt that older people have today assumed a special place in the American social policy and political landscape. They constitute a large and growing population, they are increasingly well organized, and they are the recipients of public benefits that are the envy of every other social policy constituency in the nation. This chapter reviews and assesses different theoretical approaches that may help account in all or in part for these fairly recent and remarkable developments. The organization here centers on six distinct theoretical avenues for better understanding these political and policy developments: the logic of industrialization and policy development, the role of political culture and values, the presence of working-class mobilization, the impact of individual and group participation, the weight of state structure, and the effects of policy in shaping subsequent events.

The general topic of successful aging (SA) has long been a major theme in gerontology and has been an especially prominent and growing aspect of gerontological research and program development over the past 25 years. This chapter focuses on substantial empirical research that builds on the general concept of SA to inform theory evolution and various forms of program development at the individual and community level. There has been very substantial theoretical work, over several decades, on the interrelated but differentiated dual approaches of the life-course and life-span perspectives on aging. Usual aging was seen as laden with risk of disease and disability mediated by lifestyle-related increased lipids, glucose, and blood pressure, and decreased renal, pulmonary, cardiac, immune, and central nervous system (CNS) function. A successfully aging society can be seen as one that is productive, cohesive, secure, and equitable.

Health promotion efforts will play a powerful role as we work to enhance function and reduce morbidity by intervening on modifiable risk factors such as physical activity (PA), inactivity, social engagement, and nutrition. This chapter examines the state of the art of theoretical foundations for health behavior change that are used to design and implement health promotion programs for older adults. The principles of social cognitive theory (SCT) have been used frequently in health behavior interventions. The chapter uses the ecological model as a guide to describe the level(s) targeted by each theory. It presents the most prominent multilevel approach, the social-ecological model. Recently, there has been a push toward broader ways of thinking about behavior change using structural approaches that target all levels of the social-ecological model. The chapter presents theories targeted at each level and argues for the use of multilevel interventions whenever possible.

This chapter illustrates that aging in place is richer and more dynamic than simply understanding aging as loss and place as a static physical environment. The conceptual cornerstone of environmental gerontology is Lawton and Nahemow’s Ecological Model of Aging, otherwise known as the ‘competence-press model’ of aging. The concept of aging in place has evolved from the simple homeostatic notion of person-environment (P-E) fit to a more dynamic conceptualization that considers people, places, the programs they embody, constructive selective and accommodative processes, and the goals that motivate the entire enterprise, as they all evolve over time. The ecological framework of place (EFP) identifies a variety of factors that are hypothesized to affect P-E fit, including characteristics of individuals, places, and time.

Studies in model organisms strongly support the idea that proteostasis is critical for healthy longevity and that enhanced proteostasis is associated with longevity both across species and within species. This chapter provides an overview of the evidence supporting the theory that loss of protein homeostasis is a conserved mechanism of aging. It also provides an overview of current evidence that loss of proteostasis is a central driver of aging and age-related disease, based on studies from a variety of model systems and clinical data. Although the link between loss of proteostasis and disease is strongest in age-associated neurodegenerative disorders, there is growing evidence that misfolding and aggregation of proteins also contribute to other age-related diseases, as well as functional decline in numerous tissues and organ systems accompanying the aging process. The heat shock response (HSR) has been strongly implicated in aging in several organisms, including yeast, worms, and flies.

This chapter discusses prismatic history a selective, select account of theory building in the field, which ideally stirs gerontological imaginations about future theoretical work. Several of gerontology’s founders promulgated or borrowed theories to guide research on aging. Based on work in pathology, cytology, and immunology, Metchnikoff formulated ‘phagocytosis‘, an interdisciplinary theory of aging hypothesizing that large intestinal white blood cells destroyed microbes that hastened premature senility in humans, apes, dogs, and plants; the construct anticipated various degenerative and wear-and-tear theories. Biologist Vincent Cristofalo, endorsing no unified biological theory of aging, reduced models into groupings of stochastic and developmental-genetic theories. Gerontologists demolished disengagement theory in Unripe Time. Not even a giant like Robert Havighurst could salvage parts of activity theory in order to sustain his pioneering theory of successful aging.

Social support from close relationships is one of the most well-documented psychosocial predictors of physical health outcomes. Social support is distinguishable from other health-relevant social processes including social integration and social negativity. This chapter reviews epidemiological work on social support and health, and explores the major life-span models that have implications for understanding these issues. Importantly, the link between social support and mortality was consistent across age, sex, geographical region, initial health status, and cause of death. In order to elaborate on the developmental processes over time that might impact social support from close relationships and health, a life-span model of support has been proposed that attempts to integrate prior work and models across disciplines. Most social support interventions also target individuals who are most at risk or who already have psychological, behavioral, or medical problems.