Sympathetic-parasympathetic system deregulation theory of aging.

The central nervous system, comprised of the brain, spinal cord, and nerves, includes the autonomic nervous system (ANS) that regulates involuntary functions. Within the ANS, the sympathetic and the parasympathetic nervous systems (SNS and PNS, respectively) control the same bodily functions, but in opposing directions. For example, the sympathetic nervous system elicits our "fight or flight" response, while the parasympathetic system supports "rest and repair" mechanisms in the broadest possible sense. With age, changes occur in how information is transmitted, in energetic requirements and expenditures, and in the ability to respond to change. These alterations with age result in the "hallmarks of aging", specifically including genomic instability, telomere attrition, epigenetic changes, loss of proteostasis, deregulated nutrient-sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and chronic inflammation. Understanding these age-dependent changes is essential for promoting healthy aging and longevity. We propose that, at the core of aging, there is an imbalance between the SNS and PNS, which provides opportunities for therapeutic intervention.