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According to recent Alzheimer's research from UVA Health, increased light sensitivity may be responsible for "sundowning," or the exacerbation of symptoms in the late afternoon, as well as for sleep disturbances that are thought to hasten the disease's progression.
As per the researchers, there is significant promise for both the creation of medicines and symptom management based on the new understandings of the abnormalities of the biological clock seen in Alzheimer's. For instance, Alzheimer's patients' disturbed "circadian rhythms," the body's normal daily cycle, cause caretakers to frequently struggle with the patients' unpredictable sleep habits. The latest research indicates that light therapy could be a useful technique for managing that. Further, better understanding Alzheimers effects on the biological clock could have implications for preventing the disease. Poor sleep quality in adulthood is a risk factor for Alzheimers, as our brains, at rest, naturally cleanse themselves of amyloid beta proteins that are thought to form harmful tangles in Alzheimers. Circadian disruptions have been recognized in Alzheimer's disease for a long time, but we'venever had a very good understanding of what causes them, said researcher Thaddeus Weigel, a graduate student working with Heather Ferris, MD, PhD, of the University of Virginia School of Medicines Division of Endocrinology and Metabolism. This research points to changes in light sensitivity as a new, interesting possibleexplanation for some of those circadian symptoms. Alzheimers is the most common form of dementia, affecting 50 million people around the world. Its hallmark is progressive memory loss, to the point that patients can forget their own loved ones, but there can be many other symptoms, such as restlessness, aggression, poor judgment and endless searching. These symptoms often worsen in the evening and at night. Ferris and her collaborators used a mouse model of Alzheimers to better understand what happens to the biological clock in Alzheimers disease. They essentially gave the mice jet lag by altering their exposure to light, then examined how it affected their behavior. The Alzheimers mice reacted very differently than did regular mice. The Alzheimers mice, the scientists found, adapted to a six-hour time change significantly more quickly than the control mice. This, the scientists suspect, is the result of a heightened sensitivity to changes in light. While our biological clocks normally take cues from light, this adjustment happens gradually, thus, jet lag when we travel great distances. Our bodies need time to adapt. But for the Alzheimers mice, this change happened abnormally fast. The researchers initially thought this might be because of inflammation in the brain neuroinflammation. So they looked at immune cells called microglia that have become promising targets in our efforts to develop better Alzheimers treatments. But the scientists ultimately ruled out this hypothesis, determining that microglia did not make a difference in how quickly mice adapted. (Thats not to say that targeting microglia wont be beneficial for other reasons.) Notably, the UVA scientists also ruled out another potential culprit, mutant tau, an abnormal protein that forms tangles in the Alzheimers brain. The presence of these tangles also did not make a difference in how the mice adapted. The researchers results ultimately suggest there is an important role for the retina in the enhanced light sensitivity in Alzheimers, and that gives researchers a promising avenue to pursue as they work to develop new ways to treat, manage and prevent the disease. These data suggest that controlling the kind of light and the timing of the light could be key to reducing circadian disruptions in Alzheimers disease, Ferris said. We hope that this research will help us to develop light therapies that people can use to reduce the progression of Alzheimers disease. (ANI)
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