Light sensitivity in Alzheimer’s may worsen symptoms later in the day

Light sensitivity in Alzheimer's may worsen symptoms later in the day

The Hidden Culprit Behind Sundowning in Alzheimer’s Patients

Sundowning in Alzheimer’s

Sundowning in Alzheimer’s disease patients is a symptom that occurs in the late afternoon and evening. It is characterized by increased confusion, agitation, anxiety, and mood swings. The causes of this debilitating symptom are little understood, and it has been assumed to be due to the effect of Alzheimer’s disease on the brain. However, recent research in mouse models of Alzheimer’s disease has shed new light on the subject.

Unraveling the Mystery of Sundowning

Sundowning is a distressing symptom of Alzheimer’s disease that worsens dementia symptoms in the late afternoon and evening. Many physicians recommend that patients with Alzheimer’s stick to a daily routine with consistent timings, calming activities, minimized noise, and adequate lighting in the evening. Dr. Alexander Lapa, a psychiatrist from the Rehab Clinics Group, explains that sundowning can be distressing for both the affected individual and their caregivers. It can lead to increased care needs, disrupt daily routines, and compromise the safety of the patient and others around them.

The Impact of Light Sensitivity

Despite the debilitating nature of sundowning, the cause has remained unknown for a long time. However, a recent study conducted by researchers from the University of Virginia suggests that increased light sensitivity in the retina may play a significant role.

The study focused on the retina’s specialized cells called intrinsically photosensitive retinal ganglion cells. These cells are light-sensitive but not used for vision. Instead, they signal the brain that it is daytime. The researchers discovered that Alzheimer’s disease model mice had more of these cells in their retina and could be triggered with less light compared to healthy mice.

This finding led the researchers to conclude that Alzheimer’s disease affects the retina, not just the brain. The retina’s photosensitive cells regulate circadian rhythms, communicate with the brain through the optic nerve, and rely on a light-sensitive protein called melanopsin. The researchers observed an increase in melanopsin levels in the Alzheimer’s disease model mice.

Exploring the Connection to Sleep Disturbance

Sleep disturbance is a common issue for individuals with Alzheimer’s disease. Previous research has shown that disruptions in the circadian rhythms and sleep patterns are associated with Alzheimer’s. To investigate the link between sleep disturbance and Alzheimer’s, the researchers conducted experiments using mouse models.

The researchers first exposed mice to a 6-hour shift in their exposure to daylight to simulate jet lag. Interestingly, the Alzheimer’s disease model mice returned to a normal 24-hour routine quicker than the control mice. This difference could not be attributed to the presence of microglia, brain-based immune cells, which are involved in clearing amyloid beta plaques, as reducing their number did not affect the recovery speed. Instead, the Alzheimer’s disease model mice showed greater behavioral sensitivity to changes in lighting, suggesting increased vulnerability to light reception.

Seeking Potential Treatments

The findings of the study suggest that the retina may be affected in a way that increases light sensitivity in Alzheimer’s disease. Amyloid and tau proteins, characteristic of Alzheimer’s, have also been found in the retina of patients. Additionally, the breakdown of the retinal blood barrier has been observed in Alzheimer’s patients. These discoveries provide a new perspective for addressing sundowning.

Dr. Heather Ferris, the lead author of the study, hopes to explore potential therapies in the future. Currently, physicians recommend keeping people with Alzheimer’s on a strict light, sleep, and eating schedule to maintain normal rhythms. Dr. Ferris suggests that light therapy may hold promise for alleviating sundowning symptoms. By reducing light exposure at certain times or changing the wavelength of light, these therapies could potentially prevent some behavioral changes associated with sundowning.

In the meantime, Dr. Ferris advises everyone, regardless of Alzheimer’s disease, to limit exposure to blue light from screens in the evening. Blue light is known to trigger melanopsin and disrupt sleep and circadian rhythms, making it important to manage light exposure for overall well-being.

With these new insights into the connection between sundowning and increased light sensitivity in the retina, researchers are hopeful that future studies will lead to more effective treatments and improved quality of life for individuals with Alzheimer’s disease.