Abnormal Circadian Rhythm Can Predict Parkinson’s Disease

Post by D. Chloe Chung

What's the science?

Parkinson’s disease is a debilitating neurodegenerative disease that is characterized by the loss of dopaminergic neurons in the brain in an area called the substantia nigra. In addition to severe motor symptoms, Parkinson’s patients often experience a disrupted sleep-wake cycle, sometimes early on in the disease course. However, no study has actually measured behavioral markers of circadian rhythm to find out whether disruption of the internal biological clock can precede the development of Parkinson’s disease. This week in JAMA Neurology, Leng and colleagues reported that abnormal circadian rhythm in healthy older adults can be regarded as an early sign of developing Parkinson’s disease in the future.

How did they do it?

The authors enrolled almost 3,000 healthy older males (average age of 76.3 years old) for the initial evaluation of circadian rhythm and followed up with them for the following 11 years. The participants were mostly Caucasians and lived in a community setting. At the beginning of the study, participants wore a wristband-like device that can track any movement during sleep. For a minimum of three separate 24-hour periods, the monitoring device recorded various circadian rhythm parameters of wake and rest. Sleep efficiency was determined based on the percentage of time the participants were asleep after “lights off”. Other important factors such as sleep apnea or periodic limb movement have been also taken into account. During the 11-year follow-up, participants were subject to in-person visits or questionnaires five times and reported whether they have been diagnosed with Parkinson’s disease, as well as their medication history. 

What did they find?

While none of the participants had Parkinson’s disease at the beginning of this longitudinal study, 78 out of 2930 study subjects were later diagnosed with Parkinson’s disease over the course of 11 years. After adjusting for variables such as demographics, education level, medication or substance usage, comorbidities, and baseline cognition, the authors found a strong association between the decrease in three out of four circadian rhythm parameters and the development of Parkinson’s disease later in life. Strikingly, participants who showed the most irregular circadian rhythm were three times more likely to develop Parkinson’s disease compared to those with the regular circadian rhythm. These findings indicate that decreased circadian rhythmicity can act as an important early symptom of Parkinson’s disease. 

What’s the impact?

This study is the first one to analyze a large cohort for a long time and reveal that circadian rhythm abnormalities in healthy adults are associated with their chance of developing Parkinson’s disease as they get older. Therefore, the authors suggest that the detection of abnormal circadian rhythm in healthy adults may help early prediction and diagnosis of Parkinson’s disease, ultimately allowing for early disease intervention. It will be interesting to further investigate whether circadian rhythm might directly contribute to the onset of Parkinson’s disease.

Leng et al. Association of circadian abnormalities in older adults with an increased risk of developing Parkinson disease (2020). Access the original scientific publication here.