Tag Archives: Circadian rhythm

“Sleep disturbances may be an early warning sign of Alzheimer’s”

1 Sep

A post from the blog Neurophilosophy:

“The research shows that people with Alzheimer’s, Parkinson’s and several other neurodegenerative conditions often experience sleep disturbances many decades before any symptoms appear, and that these disturbances are somehow linked to disruptions of the circadian rhythm. They include common sleeping difficulties such as insomnia, sleep apnoea, and daytime drowsiness, and some slightly more unusual ones. According to one small study published in 2011, for example, the early stages of Parkinson’s disease are characterised by alterations in the content of dreams, particularly the presence of animals and increased aggressiveness.”

Here is Dr. Greger on optimal sleep duration:

Melatonin in food and sleep quality

4 Apr

I have blogged a lot recently about the importance of sleep for cognitive performance. But what can we do to improve the quality of sleep?

Here is a video from Dr. Greger about dietary melatonin.


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Sleep is critical for brain health

3 Apr

Neuroscientifically Challenged has a good post on why sleep is important for brain health.

While at Nautilus there is a piece by  Eli Chen about the health consequences of nighttime light exposure.

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Chronotype and Academic Achievement

15 Mar

I am fascinated by chronotypes (also called circadian preference). Here is a paper just published on the relationship between chronotype and academic achievement published in the journal Learning and Individual Differences. The paper reports:


“Circadian preference has an effect on academic achievement.”


In general, earlier chronotype predicts a higher cumulative grade point average.


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Later school start time benefits students

27 Jan

A study, published in The Journal of Developmental and Behavioral Pediatrics, reports that an experimental 25 minute delay in school start time improved students’ sleep and their daytime functioning.  From the abstract:


The delay in school start time was associated with a significant (29 min) increase in sleep duration on school nights. The percentage of students receiving 8 or more hours of sleep on a school night increased to more than double, from 18% to 44%. Students in 9th and 10th grade and those with lower baseline sleep amounts were more likely to report improvements in sleep duration after the schedule change. Daytime sleepiness, depressed mood, and caffeine use were all significantly reduced after the delay in school start time. Sleep duration reverted to baseline levels when the original (earlier) school start time was reinstituted.


A modest (25 min) delay in school start time was associated with significant improvements in sleep duration, daytime sleepiness, mood, and caffeine use. These findings have important implications for public policy and add to research suggesting the health benefits of modifying school schedules to more closely align with adolescents’ circadian rhythms and sleep needs.”

One weakness of the study is that it was based on self-report data, not objective measures. In addition, it did not examine any effects on cognitive performance. However, it was a prospective experimental study that did show important effects and should be taken seriously.

Later start times for school would a relatively inexpensive intervention and is certainly worth considering.

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Blue light disrupts student’s circadian rhythm

13 Dec

I wrote again a few days ago about the dangers of artificial light. I received my copy of Education Week today with a front page story: ” ‘Blue Light’ May Impair Students’ Sleep, Studies Say”  The article cites work by Charles A. Czeisler. Here is a piece by Czeisler in the science journal Nature.

Czeisler tell us:

“Sleep is essential to our physical and mental wellbeing, so it is vital that we learn more about the impact of light consumption and other ways our 24/7 society affects sleep, circadian rhythms and health. We must then use this knowledge to develop behavioural and technical interventions to mitigate these ill effects. It is time to reassess the early assurances of Thomas Edison that using electric light “is in no way harmful to health, nor does it affect the soundness of sleep”.”

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The dangers of artificial light

11 Dec

I have written a number of times about the importance of sleep for memory. Here is an article from the magazine In These Times describing how artificial light poses a danger to our sleep wake cycles.

According to the article:

“In outdoor lighting, a cool tint has significant drawbacks. According to a 2011 study published in the Journal of Environmental Management, when blue light seeps into people’s homes at night through windows or slats in blinds, it can alter circadian rhythms and suppress melatonin production, leading to difficulty sleeping. A low melatonin level has also been linked to breast and prostate cancer. What’s more, blue light contains ultraviolet light, which cannot be seen, but can damage retinas and contribute to macular degeneration. Abraham Haim, director of the Center for Interdisciplinary Chronobiological Research at the University of Haifa and coauthor of the study, urges that “short wavelengths should be eliminated from the nocturnal spectrum.”

“According to an American Medical Association report, other health problems that may be exacerbated by the light “include obesity, diabetes, depression and mood disorders, and reproductive problems.” In 2012, the American Medical Association formally recommended that more research be conducted “on the risks and benefits of vocational and environmental exposure to light-at-night, the risk of cancer and the exacerbation of chronic diseases.””

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