What Is the Role of Reserve Capacity?

A robust, linear association between socioeconomic status (SES) and health has been identified across many populations and health outcomes. This relationship is typically monotonic, so that each step down the SES hierarchy brings increased vulnerability to disease and premature mortality. Despite growing attention to health disparities, scientists and policymakers have made little progress toward confronting their causes and implementing effective solutions. Using the reserve capacity model (Gallo & Matthews, 2003) as an organizing framework, the current article examines the contribution of resilient psychosocial resources to socioeconomic disparities in physical health. Findings suggest that deficient psychosocial resources, such as low perceptions of control and social support, may be one of many factors that connect low SES with poor health. Additional research is needed to test these relationships and their underlying mechanisms, to consider interventions to enhance reserve capacity, and to evaluate the efficacy of such efforts in fostering resilience to socioeconomic hardship. KEYWORDS—health disparities; socioeconomic status; resources; reserve capacity The powerful association between socioeconomic status (SES) and physical health has been recognized for many decades. Whether defined according to educational attainment, income, or occupational status, lower SES is associated with diverse disease endpoints and with premature mortality. The relationship is typically monotonic, such that each step down the socioeconomic gradient brings increased vulnerability to health problems, including functional impairment, poor self-rated health, disease-specific morbidity, and premature mortality. Thus, the robust health impact of SES is not solely a reflection of the poor health suffered by those in poverty; it transcends every level of the socioeconomic hierarchy. Despite growing attention to health disparities, efforts to confront their causes have lagged behind. In part, this is due to our limited understanding of the factors that underlie health disparities. The picture is complicated, as SES shapes virtually every aspect of health risk, including health-care access and quality, environmental exposures, community characteristics, health behaviors, and psychosocial functioning. The elimination of health disparities will require widespread involvement from multiple organizations, agencies, and systems—federal and local public health officials, the health-care industry, policymakers, human services agencies, the educational system, the justice system, the media, community members, and so on. Psychological scientists can facilitate these efforts by uncovering key psychosocial and behavioral pathways and translating their findings into targeted prevention and intervention strategies. THE RESERVE CAPACITY MODEL We developed the reserve capacity model (Gallo, Bogart, Vranceanu, & Matthews, 2005; Gallo & Matthews, 2003) as a broad organizing framework for research examining psychosocial variables in SES-related health disparities. As shown in Figure 1, this model incorporates three fundamental psychosocial pathways. First, as compared to their higher-SES counterparts, individuals with low SES endure more stress, which in turn predicts physical-health outcomes such as cardiovascular disease and premature mortality (arrows A, C, and M). Second, increased negative emotions and reduced positive emotions (well-known correlates of stressful environments) may contribute to the relationships among SES, stress, and health (arrows B and J). Compared to their higher-SES counterparts, individuals with lower SES tend to report greater depression, anxiety, and hostility—emotional factors that subsequently relate to health risk factors and outcomes (arrows L and M). Finally, individuals with low SES may be more physiologically and emotionally reactive to stress. Based on resource models of stress (Hobfoll, 2001) and healthy aging, we proposed that this heightened vulnerability occurs because individuals with low SES have few Address correspondence to Linda C. Gallo, SDSU/UCSD Joint Doctoral Program in Clinical Psychology, San Diego State University; 6363 Alvarado Court, Suite 103, San Diego, CA 92120; e-mail: [email protected]. CURRENT DIRECTIONS IN PSYCHOLOGICAL SCIENCE Volume 18—Number 5 269 Copyright r 2009 Association for Psychological Science resilient psychological and social resources (i.e., reserve capacity) with which to manage frequent environmental demands (arrow D). In addition, stress combined with low resources can generate further stress and resource deficiencies, fostering spiraling stress and losses (arrow K; Hobfoll, 2001). Importantly, research suggests that resilient psychosocial factors also relate directly with health, so that reserve capacity could moderate (arrow E) or mediate (arrows F and G) the relationships among SES, stress, and emotional and physical health. The reserve capacity model emphasizes resilient personal and social factors that have been related to SES and physical health and have been shown to alter emotional and physical stress responses. These include interpersonal resources, such as social support and social integration, and intrapersonal resources, such as perceived control (i.e., mastery), optimism, and self-esteem. Ultimately, resources are believed to affect health via converging biological and behavioral risk pathways. For example, they can dampen physiological stress responses that foster disease vulnerability, or they can help attenuate stress perceptions, facilitate expectancies positive outcomes, and promote adaptive coping. Low resources and stress also relate to unhealthy behaviors, such as smoking, poor nutrition, and reduced sleep. In turn, these interrelated biobehavioral pathways can promote a host of health problems, including chronic and infectious diseases and premature mortality (Miller, Chen, & Cole, 2009). Much of the research that informed the reserve capacity model provided indirect support, since few studies prior to 2002 had concurrently examined associations among SES, psychosocial factors, and physical health. Although a more recent review suggests that the literature base remains somewhat limited (Matthews, Gallo, & Taylor, in press), studies examining contributions of resilient resources are particularly promising. When combined with other research, these findings suggest that reserve capacity may represent a modifiable intermediate pathway connecting SES with health. The current manuscript describes what we have learned to date about the roles of resilient resources in associations among SES, stress, and physical health. As shown in Figure 2, we examine studies that have tested whether resilient resources mediate the association between SES and health outcomes—that is, if the impact of SES on health occurs, in part, through an indirect pathway via a relationship with resource variables and their subsequent effects on health risk (arrows N, O, P). Where possible, we report the proportion of the SES effect attributable to resource variables, in order to provide information about the importance, or magnitude, of the mediational pathway. We also examine studies that have addressed moderation, or the possibility that resources alter the relationship between SES and health risk (arrow Q)— for example, by attenuating the unhealthy effects of stressful low-SES environments. Our discussion includes examination of subjective as well as objective health outcomes. However, since a common underlying construct (e.g., negative affectivity) could influence perceptions of both resources and self-rated health, studies with subjective endpoints should be viewed more tenReserve Capacity Tangible Intrapersonal Interpersonal ↑ A Low SES ↓Access to Resources ↓ Position in Social Hierarchy Stress ↑Threat of or Actual Loss/Harm ↓Potential for or Actual Benefit/Gain TIME Intermediate Paths Behavioral Diet Physical Activity Substance Use Sleep Physiological SAM/HPA Activity Immune Function Metabolic Function