Circadacare logo

Exploring the link between circadian cycles and Alzheimer’s

While the exact mechanisms underlying the relationship between circadian rhythms and Alzheimer’s disease are still being unravelled, it is clear that disruptions in sleep-wake cycles and circadian rhythms play a significant role in the development and progression of the disease. Understanding this connection provides valuable insights for potential prevention and treatment strategies.

Further research is needed to explore the optimal approaches for regulating circadian rhythms and mitigating the risk of Alzheimer’s disease. Collaborative efforts between neuroscientists, sleep experts, and clinicians are crucial to unravel the complexities of this relationship and develop targeted interventions.

Introduction to Alzheimer’s: While Alzheimer’s disease’s exact cause is still under investigation, researchers have made significant progress in understanding the various factors that contribute to its development. One emerging area of study focuses on the intricate relationship between circadian cycles and Alzheimer’s disease.

Understanding circadian rhythms: Before we delve into the connection, let’s first understand what circadian rhythms are. Circadian rhythms are natural, internal processes that regulate the sleep-wake cycle and numerous physiological functions in living organisms, including humans. These rhythms are regulated by an internal biological clock located in the suprachiasmatic nucleus (SCN) of the brain; light is the single most potent trigger for this.

Circadian rhythms and Alzheimer’s: Recent studies have highlighted a strong association between disrupted circadian rhythms and Alzheimer’s disease. Individuals with Alzheimer’s often experience disturbances in their sleep patterns, with fragmented sleep, increased nighttime wakefulness, and daytime drowsiness. These disruptions can occur years before the onset of cognitive symptoms and may even serve as early indicators of the disease.

The Link: Beta-Amyloid and Tau Proteins

Two key hallmarks of Alzheimer’s disease are the accumulation of beta-amyloid plaques and tau protein tangles in the brain. Interestingly, emerging research suggests that circadian disruptions may contribute to the build-up of these pathological markers.

Beta-Amyloid: Disruptions in circadian rhythms can lead to an imbalance in the production and clearance of beta-amyloid proteins. Normally, during sleep, the brain clears away excess beta-amyloid, preventing its accumulation. However, when sleep is fragmented or reduced, as seen in circadian rhythm disturbances, the clearance process becomes less efficient. This can result in the buildup of beta-amyloid plaques, which are toxic to brain cells and contribute to Alzheimer’s pathology.

“Taking care of our sleep or circadian rhythms – sometimes called good sleep hygiene – may be able to reduce amyloid beta burden over our lifespan… Reducing amyloid burden could mean a reduction in Alzheimer’s symptoms or a delay in the onset or progression of the disease.” Dr Jennifer Hurley

Tau protein: Disruptions in circadian rhythms also affect the phosphorylation and clearance of tau proteins. Tau proteins play a crucial role in maintaining the stability and structure of neurons. However, when these proteins become abnormally phosphorylated, they form tangles, impairing cellular communication and triggering neuronal damage. Circadian rhythm disturbances have been shown to disrupt the clearance of phosphorylated tau proteins, leading to their accumulation and contributing to Alzheimer’s progression.

Understanding the link between circadian rhythms and Alzheimer’s disease opens up new avenues. Here are a few potential implications:

Sleep hygiene: Promoting healthy sleep habits, including maintaining a consistent sleep schedule, creating a conducive sleep environment, and avoiding factors that disrupt sleep, may help regulate circadian rhythms and reduce the risk of Alzheimer’s disease.

Light: Light exposure, particularly in the morning, can help synchronise circadian rhythms and improve sleep-wake cycles. True circadian lighting may prove beneficial in regulating circadian disruptions associated with Alzheimer’s.

Lifestyle modifications: Maintaining a healthy lifestyle that includes regular exercise, a balanced diet, and managing stress can have a positive impact on circadian rhythms and overall brain health. These lifestyle factors may help reduce the risk of Alzheimer’s disease or slow its progression.

While sleep disturbances often arise before Alzheimer’s disease, Hurley and many other scientists suspect there is a complex interplay between the two. Disrupting sleep and circadian rhythms allowed amyloid beta to build up, Hurley said, but this in turn damaged brain cells that ran the circadian clock, causing further accumulation of amyloid beta.

The understanding from key studies points to the importance of promoting healthy circadian cycles and, in turn, sleep cycles in older adults and those living with dementia and how circadian lighting interventions can play a critical role for wellbeing.