How useful are biomarkers for the diagnosis of Alzheimer’s disease and especially for its therapy?

Alzheimer’s disease (AD) is a slowly progressive neurodegenerative disease with no available effective treatment. It is possible to distinguish an early-onset AD that affects a limited number of subjects of young age, and a sporadic or late-onset form of the disease that affects the vast majority of subjects who are diagnosed with AD. As life expectancy has increased considerably over the past century, the number of people diagnosed with AD has grown exponentially. So, AD and AD-related pathologies represent a huge social and economic burden. The number of individuals waiting for effective disease-modifying therapy is impressive. It is estimated that 50 million people worldwide live with dementia, the majority of these cases are caused by AD (World Health Organization, 2021). In the US about 6 million individuals are living with AD, and more than 9 million people are in EU member states (OECD and European Union, 2020). The costs of health care and long-term care are substantial. Given this massive societal impact, enormous efforts have been made to understand the pathogenetic mechanisms of the disease with the hope of identifying new targets and, therefore, developing effective drugs. However, despite huge preclinical and clinical scientific efforts, therapeutic advances are truly modest, and the clinical practice is still anchored to the use of drugs modulating the cholinergic and glutamatergic systems.