Duntley notes that older adults often sleep less and have fewer periods of deep slumber. A number of factors linked to aging, such as reduced exercise levels, can disrupt the normal daily patterns of sleep and waking. These disruptions often become more pronounced as individuals age. The risk of Alzheimer's disease also increases with age.
Scientists studied three sets of subjects: a group age 60 and older who tested positive for the presence of amyloid beta plaques in the brain; a group in the same age range who did not have plaques; and a group of healthy persons age 18-60.
Researchers used a spinal tap to monitor amyloid beta in the spinal fluid hourly for 24 to 36 hours, and videotaped patients' activities and monitored their brain activity during that period.
In the group with brain plaques, amyloid beta levels were close to constant. But in the other two groups, the levels regularly rose and fell in a snakelike, sinusoidal pattern. The highs and lows of this pattern were much more pronounced in younger subjects.
Lead author Yafei Huang, PhD, statistical data analyst, reviewed the subjects' activities during the monitoring period at 30-second intervals. She grouped them into categories such as eating or drinking, watching television, using the bathroom, and using a computer or text messaging.
None of these activities could be closely correlated with changes in amyloid beta levels. But peaks in sleep and wakefulness, assessed both by videotape and by records of patients' brain activity levels, consistently occurred before the peaks and valleys of amyloid beta levels.
Researchers are currently testing if deliberate interruption of sleep in young healthy subjects disrupts the normal daily decrease in spinal amyloid beta.Sc
|Contact: Michael C. Purdy|
Washington University School of Medicine