IL6 and Alzheimer disease: For example, levels of proinflammatory factors such as IL-6 are associated with depression, fatigue, and cognitive impairment and are elevated in Alzheimer’s and Parkinson’s patients.50,180 Accelerated epigenetic aging has also been shown to be associated with the development of neurodegenerative diseases.181 Astrocytes in aged brains also express more significant levels of p16 than those in young brains.182 Cellular senescence also prompts a physiological aging shift into neurodegeneration.183 Alzheimer’s disease (AD) is a distinct neurodegenerative disease associated with immunosenescence.