Alzheimer’s disease (AD) is the leading cause of dementia worldwide. The disease is characterized by the abnormal accumulation of amyloid β (Aβ) protein creating neuritic plaques, hyperphosphorylated tau (p-tau) protein forming intracellular tangles, and neuronal degeneration. Pathological changes related to abnormal Aβ and p-tau accumulation may begin more than fifteen years before the clinical diagnosis of AD is made. The glymphatic system is the brain’s waste clearance pathway that prevents the accumulation of these abnormal proteins and macromolecules. Glymphatic clearance is negatively affected by physiological conditions such as sleep deprivation, and pathological conditions such as traumatic brain injury and hemorrhagic strokes. These physiological and pathological conditions are strong risk factors for AD. In conclusion, impaired glymphatic clearance is an important pathogenetic mechanism for AD.

Behavioural environment and behavioural responses of an individual are known to affect multiple aspects of physiology including neuroendocrine and growth factor signalling, angiogenesis, stem cell dynamics, tissue homeostasis, and maintenance. Despite substantial evidence, the role of behaviour-physiology interface in human health and disease remains underappreciated. The hypothesis proposed here suggests that deficiencies of certain behaviours that have evolved to become essential or “vitactions” can potentially trigger multiple health problems. Altered growth factor expression because of vitaction deficiencies affects angiogenesis and vascular function, neuronal maintenance, transport of glucose and other nutrients to the brain, mitochondrial function, oxidative stress, inflammation, and protein aggregation dynamics all implicated in Alzheimer’s disease (AD). Exercise is already known to be effective in prevention of AD. The hypothesis suggests that it is the behavioural component of exercise over mechanical activity and calorie burning that has crucial effects on brain health through multiple signalling pathways. Similar to vitamin deficiencies, where supplying the deficient vitamin is the only effective solution, for vitaction deficiencies supplying the deficient behavioural stimuli through behaviourally enriched exercise can be the most effective remedy.

Currently, the predominant targets for the treatment of Alzheimer’s disease (AD) are the main components of the two pathological structures: senile plaques (composed of amyloid beta peptide aggregates) or neurofibrillary tangles (constructed of tau protein polymers). However, the existence of adequate disease modifiers based on such targets is discussed. In this special issue, it has been suggested to search for new possible targets for AD therapy. This contribution tries to analyze non-neuronal tissues (periphery) to identify potential factors (target) involved in the development of AD.

There is no approved drug capable of halting the progression of the most prevalent neurodegenerative disorders, namely Alzheimer’s disease (AD) and Parkinson’s disease (PD). Current therapeutic strategies focus mainly on the inhibition of the formation of protein aggregates and their deposition in the central nervous system. However, after almost a hundred years, proper management of the disease is still lacking. The fact of not finding effective management tools in the various clinical trials already carried out suggests that new hypotheses and strategies should be explored. Although vast resources have been allocated to the investigation of protein aggregates and the pathophysiology is now better understood, clues to the actual etiology are lacking. It is well known that brain homeostasis is of paramount importance for the survival of neurons. Drugs that target the periphery are often not subject to evaluation for their potential effect on the central nervous system. While acute treatments may be irrelevant, pills used for chronic conditions can be detrimental to neurons, especially in terms of progressive damage leading to a long-term decline in neuronal survival. Due to the lack of advances in the search for a curative treatment for neurodegenerative diseases, and the lack of new hypotheses about their etiology, a novel hypothesis is here proposed. It consists of assuming that the effects of the drugs most commonly used by the elderly, such as antihypertensive, hypoglycemic, and hypocholesterolemic, could have a negative impact on neuronal survival.