1: The two most feared diseases in the modern world are dementia and cancer. “Both are related to inadequate sleep,” writes Matthew Walker in Why We Sleep: Unlocking the Power of Sleep and Dreams.  

So far this week, we’ve looked at the connection between a lack of sleep and auto fatalities as well as anger and hostility. Today we look at the link between dementia and sleep. “Lack of sleep is becoming recognized as a lifestyle factor contributing to your risk of developing Alzheimer’s disease,” Matthew writes.

More than 40 million people currently suffer from this debilitating disease. “That number has accelerated as the human life span has stretched, but also, importantly, as total sleep time has decreased,” notes Matthew. Today, one in ten adults over sixty-five now suffers from Alzheimer’s disease. 

2: Sleep quality deteriorates as we age, which has been connected to a decline in memory. The disruption of deep sleep is far more exaggerated with Alzheimer’s patients.  

“More telling, perhaps, is the fact that sleep disturbance precedes the onset of Alzheimer’s disease by several years, suggesting that it may be an early-warning sign of the condition, or even a contributor to it,” Matthew writes. “While much remains to be understood, we now recognize that sleep disruption and Alzheimer’s disease interact in a self-fulfilling, negative spiral that can initiate and/or accelerate the condition.”

In fact, more than 60 percent of patients with Alzheimer’s disease also have at least one clinical sleep disorder. “Insomnia is especially common, as caregivers of a loved one with Alzheimer’s disease will know all too well,” he notes.

Matthew’s research at the University of California, Berkeley has shown the connection between the impairment of deep-sleep and Alzheimer’s: “And it was not just a general loss of deep sleep, which is common as we get older, but the very deepest of the powerful slow brainwaves of NREM sleep that the disease was ruthlessly eroding,” he writes.

3: The research of Dr. Maiken Nedergaard at the University of Rochester complements the findings above, showing how “inadequate sleep and the pathology of Alzheimer’s disease interact in a vicious cycle,” notes Matthew.

Deep sleep is not only critical to consolidating new memories but also “for removing dangerous metabolic contaminants generated by the hard work performed by neurons in [our] brain,” he writes. “Phrased differently, and perhaps more simply, wakefulness is low-level brain damage, while sleep is neurological sanitation.

“So what does this have to do with Alzheimer’s disease?” Matthew asks. One piece of “toxic debris” evacuated during deep sleep is the poisonous amyloid protein associated with the disease. When there is not enough deep sleep, the protein remains.

“The loss of deep NREM sleep caused by this assault therefore lessens the ability to remove amyloid from the brain at night, resulting in greater amyloid deposition. More amyloid, less deep sleep, less deep sleep, more amyloid, and so on and so forth,” he explains.

Matthew warns that while insufficient sleep is only one of several risk factors, “Getting too little sleep across the adult life span will significantly raise your risk of developing Alzheimer’s disease,” he writes. “Sleep alone will not be the magic bullet that eradicates dementia. Nevertheless, prioritizing sleep across the life span may be a significant factor for lowering Alzheimer’s disease risk.

He concludes with an observation: “Parenthetically, and unscientifically, I have always found it curious that Margaret Thatcher and Ronald Reagan—two heads of state that were very vocal, if not proud, about sleeping only four to five hours a night—both went on to develop the ruthless disease.”


Reflection: Am I getting enough sleep? If not, what am I going to do about it?

Action: Journal about my answers to the questions above.

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