The timing of sleep (known as circadian rhythm) is under the control of the hypothalamus (a part of the brain about the size of a dime directly behind the eyes and above the pituitary). The most important input to this “biological clock” is light information from the retina. In newborn infants our biological clock has not yet been set and the pattern of sleep is somewhat random (known as irregular circadian rhythm). Over the first several weeks of life light input from the retina eventually sets the biological clock and the baby’s most dominant sleep period is at night. Over the next couple of years naps become more consolidated and eventually disappear by three to five years old. Patients with dementia face a number of challenges to the control of sleep rhythms. One challenge is gradual loss of brain cells in the biological clock. In addition, there may be gradual degeneration of the retina due to conditions such as macular degeneration or decreased light input to the eyes from conditions such as cataracts. These problems predispose to the patient reverting to an irregular circadian rhythm. This irregular pattern of sleep is the most common reason that patients with dementia ultimately can not be cared for at home resulting in placement in a nursing home. It is critically important for patients with dementia to have activity during the daytime and exposure to light to allow for more normal sleep patterns for their health and for the well-being of their caregivers. Engaging in daily activities such as activities provided at St. Agnes Center is a crucial element in maintaining the function of the biological clock.
James W. Kozelka, M.D., Ph.D.
Board Certified Neurologist