Alzheimer’s may worsen in patients facing ‘jet lag’ from light exposure changes, study suggests

Alzheimer’s disease symptoms may worsen in some patients due to light exposure changes, according to a new study that may lead to new therapies for treating the debilitating neurological condition.

The new research, published recently in the journal Frontiers in Aging Neuroscience, says enhanced light sensitivity could contribute to “sundowning”, or the worsening of Alzheimer’s symptoms late in the day, and may spur sleep disruptions thought to contribute to the disease’s progression.

The findings, according to researchers from the University of Virginia in the US, provide new insights into the disruptions of the biological clock seen in Alzheimer’s patients.

Alzheimer’s disease is the most common form of dementia, which affects over 50 million people around the world, characterised by progressive memory loss to the point that patients may forget their own loved ones and have trouble managing their daily lives.

In the new study, scientists used a mouse model to better understand what happens to the body’s natural biological clock called the circadian rhythm in Alzheimer’s patients.

Researchers gave the mice “jet lag” by altering their exposure to light and examined how it affected their behaviour.

They say the new study could help both in the development of new Alzheimer’s treatments as well as symptom management.

Caregivers often have trouble with erratic sleep patterns in Alzheimer’s patients due to their altered natural biological clocks called circadian rhythms.

And the new study suggests therapy using light exposure could be developed to help manage such sleep cycle disruptions in patients.

“Circadian disruptions have been recognized in Alzheimer’s disease for a long time, but we’ve never had a very good understanding of what causes them,” study co-author Thaddeus Weigel said.

“This research points to changes in light sensitivity as a new, interesting possible explanation for some of those circadian symptoms,” he added.

In the latest research scientists found that Alzheimer’s mice reacted very differently to light exposure changes than did regular mice.

Researchers say Alzheimer’s mice adapted to a six-hour time change significantly more quickly than the control mice, likely due to their heightened sensitivity to changes in light.

The body’s biological clocks take cues from light, adjusting gradually, but for the Alzheimer’s mice, scientists suspect this change happened abnormally fast.

The findings point to a likely important role for the eye’s retina in the enhanced light sensitivity in Alzheimer’s.

Scientists say the retina may be a promising avenue to pursue future 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 Alzheimer’s disease,” study author Heather Ferris said.

“We hope that this research will help us to develop light therapies that people can use to reduce the progression of Alzheimer’s disease,” Dr Ferris added.