The Aging Brain

According to the United States Department of Health and Human Services Administration on Aging, more than 14 percent of the US population is 65 or older, a percentage that is predicted to steadily increase over the next several decades. The rapid growth of this segment of the population is not a phenomenon limited to the United States — the global population is aging as well. A recent report by the Population Division of the United Nations Department of Economic and Social Affairs indicates the worldwide number of individuals ages 60 and older is set to double by 2050. As this demographic shifts, certain medical challenges are anticipated to heavily affect the aging members of the world, as well as the caregivers and loved ones who help support them. This issue of the Yale Journal of Biology and Medicine (YJBM) addresses some of the largest concerns and challenges facing this expanding community of elderly individuals. The degeneration of the brain, loss of memory, compromised motor functions, loss of vision, slow injury recovery, and the effect of chronic substance abuse are issues that are essential to this community. Understanding the underlying biological mechanisms of physiological changes that occur in later stages of life is critical to diagnosing and treating age-related disease. This issue on The Aging Brain provides various insights into the means to more effectively treat and care for this valued segment of the population. The Alzheimer’s Association suggests that one in three senior citizens in the US will be affected by Alzheimer’s disease (AD) and other forms of dementia. Although there is no cure for AD, scientific studies in the past decade have provided insight into the causes of neural damage and potential treatment approaches. To better clarify the current gaps in our knowledge surrounding the sequence of pathogenic events in AD and elucidate the current efforts and studies around these events, this issue begins with an interview with Dr. Christopher van Dyck, the Director of the Alzheimer’s Disease Research Unit at the Yale School of Medicine. Dr. van Dyck discusses current neuroimaging studies working to understand disease pathogenesis in vivo and efforts to test new AD therapeutics in humans. Arbor, LaFontaine, and Cumbay discuss new information regarding amyloid beta structure and protein processing pathways, as well as obstacles hindering scientists from understanding the underlying causes of dementia and developing curative therapies. Tincer et al. describe the potential uses of neural stem cells and progenitor cells in treating AD, a method that holds great promise in reversing neural degeneration that occurs with the disease. Another neurodegenerative disease primarily affecting the aging population is Parkinson’s disease (PD). Patients with PD lose dopaminergic neurons in the substantia nigra, which causes problems with speech, movement, and balance. Borovac provides a clinically relevant review of the current dopamine agonists used as therapeutic agents to treat the symptoms of PD. While some disorders primarily affect certain regions of the brain, it is also important to recognize the interconnectivity and effects that different systems in the brain can have on each other. Mohan et al. introduce the clinical significance of the brain’s Default Mode Network and its role in various neurological and neuropsychiatric disorders, including AD. This article provides a unique perspective on how different regions of the brain interact and the effect these interactions have on the development and occurrence of symptoms. O’Callaghan and Kenny explore the neural control of the cardiovascular system and the various links between neurocardiovascular instability and cognitive decline often seen in dementia. Co-occurrence of various neurocardiovascular symptoms and neurodegeneration as highlighted in this article is common, but has not been explicitly discussed in the literature. This review compiles evidence from many studies in a detailed description of the pathophysiology and emphasizes that,