Role of social factors on cell death, cerebral plasticity and recovery after stroke

Abstract

Stroke is a serious global health care problem. It is now is the fourth leading cause of death and the primary cause of adult disability in the United States. Substantial evidence from both experimental and clinical studies has demonstrated that social isolation (SI) can increase stroke incidence and impair recovery. Epidemiological studies demonstrate that an increasing number of patients are living alone, and as the aging population increases, loneliness will only increase in prevalence. SI is increasingly identified as an independent risk factor for all-cause mortality. In contrast, individuals with high levels of social support exhibit more rapid and extensive functional and cognitive recovery after a wide variety of pathological insults, including stroke. Clinical data suggests that SI is an important risk factor for increased mortality and delayed functional recovery following ischemic stroke. Attesting to the importance of mortality and behavioral factors in stroke outcome is that these same effects can be reproduced in animal models of experimental stroke. This has allowed researchers to identify several mechanistic changes that occur with affiliative interactions. These include decreased systemic inflammation, elaboration of growth factors including brain derived neurotropic factor (BDNF), enhanced neurogenesis, and improved neuroimmune responsiveness in group housed animals. These may mediate the beneficial effects of social interaction on improving stroke recovery and reducing neuronal death. In this review we provide an overview of the effects of SI on ischemic injury and recovery and discuss their clinical and therapeutic implications.

Figure 1. Pathway implied in stroke outcomes influenced by social isolation and paired housing

Schematic of postulated pathway and possible mechanisms by which pair housing regulates stroke outcome. Blue shading represents factors associated in cell death or survival. Green shaded factors are associated with recovery. The yellow shaded area indicates processes on which social interaction have beneficial effects during stroke onset and recovery.