People with Alzheimer’s disease are known to have disturbances in their internal body clocks.
The disturbances could affect the sleep/wake cycle and may increase the risk of developing the disorder.
Recent research at Washington University in St. Louis shows that such body clock disruptions also occur much earlier in people whose memories are intact but whose brain scans show early signs of Alzheimer’s.
The findings may help doctors identify people at risk of Alzheimer’s earlier than currently is possible.
That’s very important because Alzheimer’s damage can take root in the brain 15 to 20 years before clinical symptoms appear.
The researchers also conducted a separate study in mice, which shows that similar body clock disruptions made amyloid plaques develop in the brain, which is linked to Alzheimer’s.
Previous studies have found that levels of amyloid fluctuate during the day and night.
Amyloid levels decrease during sleep, and research has shown that levels increase when sleep is disrupted or when people don’t get enough deep sleep.
In the current study, the researchers tracked body clock in 189 cognitively normal, older adults with an average age of 66.
Some had positron emission tomography (PET) scans to look for Alzheimer’s-related amyloid plaques in their brains.
Others had their cerebrospinal fluid tested for Alzheimer’s-related proteins. And some had both scans and spinal fluid testing.
Of the participants, 139 had no evidence of the amyloid protein that signifies preclinical Alzheimer’s.
Most had normal sleep/wake cycles, although several had body clock disruptions that were linked to an advanced age, sleep apnea or other causes.
But among the other 50 people, who either had abnormal brain scans or abnormal cerebrospinal fluid, all experienced significant disruptions in their internal body clocks.
Disruptions in the sleep/wake cycle remained even after the researchers statistically controlled for sleep apnea, age, and other factors.
The researchers found that people who experienced short spurts of activity and rest during the day and night were more likely to have evidence of amyloid buildup in their brains.
These findings in people reinforce mouse research. To disrupt the animals’ circadian rhythms, the team disabled genes that control the circadian clock.
The researchers said it’s too early to answer the chicken-and-egg question of whether disrupted circadian rhythms put people at risk for Alzheimer’s disease or whether Alzheimer’s-related changes in the brain disrupt circadian rhythms.
Their findings are published in the journal JAMA Neurology and The Journal of Experimental Medicine.
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