Chronic Sleep Disturbance May Trigger Alzheimer's Disease

New research suggests that people whose sleep is chronically disturbed may be at increased risk of early-onset dementia or Alzheimer’s disease. Domenico Praticò, professor of pharmacology and microbiology/immunology at Temple University’s School of Medicine, and colleagues studied the effects of chronic sleep disturbances on a transgenic mouse model of Alzheimer's disease. The study began when the mice were approximately 6-months old – the equivalent of an adult human in their 40s. One group of mice was exposed to 12-hours of light and 12-hours of darkness, while a second group was subjected to 20-hours of light and just 4-hours of darkness, which greatly reduced their amount of sleep. At the end of the 8-week-long study period, the researchers found that the mice in the second group demonstrated significant impairment in their working and retention memory, as well as their learning ability. Examination of the animals’ brains revealed no significant differences in amyloid plaque deposits between the two groups, however the second group of mice had a significant increase in the amount of tau protein that had phosphorylated and formed tangles inside the brain's neuronal cells. "Because of the tau's abnormal phosphorylation, the sleep deprived mice had a huge disruption of this synaptic connection," said Professor Praticò. "This disruption will eventually impair the brain's ability for learning, forming new memory and other cognitive functions, and contributes to Alzheimer's disease." The fact that the sleep deprived mice developed the Alzheimer's brain pathology earlier than the mice that were not deprived, suggests that chronic sleep disturbance acts as a trigger that accelerates pathological processes associated with dementia and Alzheimer’s disease. Professor Praticò concluded: "We can conclude from this study that chronic sleep disturbance is an environmental risk factor for Alzheimer's disease."