Background: Alzheimer's Disease (AD) is often accompanied by severe sleep problems and
circadian rhythm disturbances which may to some extent be attributed to a dysfunction in the biological
clock. The 24-h light/dark cycle is the strongest Zeitgeber for the biological clock. People with AD,
however, often live in environments with inappropriate photic Zeitgebers. Timed bright light exposure
may help to consolidate sleep- and circadian rest/activity rhythm problems in AD, and may be a low-risk
alternative to pharmacological treatment.
Objective & Methods: In the present review, experts from several research disciplines summarized the
results of twenty-seven light intervention studies which used wrist actigraphy to measure sleep and circadian
activity in AD patients.
Results: Taken together, the findings remain inconclusive with regard to beneficial light effects. However,
the considered studies varied substantially with respect to the utilized light intervention, study design,
and usage of actigraphy. The paper provides a comprehensive critical discussion of these issues.
Conclusion: Fusing knowledge across complementary research disciplines has the potential to critically
advance our understanding of the biological input of light on health and may contribute to architectural
lighting designs in hospitals, as well as our homes and work environments.