Newsletter #147: The Power of Sleep, and the Promise of Personalized Health
Happy weekend friends, and welcome to the latest edition of the humanOS newsletter!
This week, we got some insight into the impact of sleep and circadian rhythms on the brain. We learned that inadequate sleep dramatically increases risk of dementia, and that irregular sleep schedules may make you more susceptible to depression (meaning that when you sleep might matter as much as how much).
We also discovered that seasonal changes in light exposure may affect opioid receptors in the brain, which in turn could affect mood. So, if you feel kind of grouchy this time of year, this might be a reason why - and might be something that you can change.
Finally, we have discovered an exciting tool that can help you optimize your health - using a personalized approach - which we think y’all are going to really like. 👀
Scroll down to learn more! 👇🏼
This Week’s Research Highlights
☀️ Seasonal changes in length of daylight hours affects the number of opioid receptors in the brain, and may play a role in winter blues.
It is well understood that seasons affect how we feel, and our interactions with others (or lack thereof). Some evidence suggests that gradual changes in various neuroreceptor systems in response to daylight exposure may play a role. In this study, researchers first analyzed scans from 204 human volunteers who had been scanned with Positron Emission Tomography (PET). Specifically, these subjects had had a small dose of radioactive tracer that binds to the brain’s opioid receptors injected into their blood, making it possible to visualize and quantify opioid receptor signaling. The researchers calculated daylength for when each PET image was acquired, and found that seasonally varying daylength influenced brain opioid receptor availability, with the highest binding at intermediate daylengths. To figure out whether daylight was playing a causal role, they then investigated experimentally whether such variability in daylength affected brain availability in rodents. They measured opioid receptors in rats when the animals were kept in standard conditions where only the length of daylight hours was changed, and found similar results. Importantly, alterations in opioid receptors were most prominent in regions of the brain that control emotions and sociability. It seems likely that these shifts in the opioid receptor system, driven by changes in daylight hours, could play a role in seasonal affective disorder.
🧠 Older adults who get inadequate sleep are at much greater risk of developing dementia.
Researchers used nationally representative data collected from older adults participating in the National Health and Aging Trends Study (NHATS), a longitudinal study of Medicare beneficiaries (n=2610). Participants answered detailed sleep questionnaires addressing multiple aspects of their sleep patterns. Researchers collected information on patient outcomes for up to five years after the surveys were completed to analyze how aspects of sleep influenced health and mortality. The researchers determined that both sleep latency (how long it takes to fall asleep) and sleep duration were strongly associated with incident dementia. Taking thirty minutes or longer to fall asleep was linked to a 45% greater risk of developing dementia, and nightly sleep of five hours or less was associated with double the risk of dementia, when compared to those who reported getting 7-8 hours of sleep per night. Sleep disturbance and inadequate sleep were also linked to increased all-cause mortality.
😴 An irregular sleep schedule may increase risk of depression as much as not getting enough sleep.
Researchers examined direct measurements of sleep and mood from first year medical residents (n=2115). Medical interns are a useful population for examining the relationship between mental health and sleep timing, as they are routinely subjected to very long work days and irregular work schedules, which in turn inevitably alters their sleep schedules.
The participants were outfitted with wearable devices to objectively measure sleep, and their daily mood and depressive symptoms were assessed via a smartphone app. They found (unsurprisingly) that those who got the fewest hours of sleep and who regularly stayed up late scored higher on depressive symptoms and lower on daily mood. However, participants who were shown to have variable sleep schedules were also more likely to score higher on depression symptom questionnaires, and to have lower mood ratings, and the magnitude of effect was similar as not getting enough sleep. To optimize mental health, sleep should ideally be not just sufficient, but also consistent.
Question of the Week
🤔 Light has an underappreciated impact on health and performance. What does your pattern and intensity of light exposure - in both day and night - look like, and what tweaks could you make to improve it?
Podcasts We Loved This Week
- Matthew Wolf-Meyer: Rethinking sleep in modern American life. Via Sleep Junkies.
- Greg Potter: Why sleep is critical for immune health. Via Nourish Balance Thrive.
Products We're Interested In
InsideTracker
In regards to health, individuals respond uniquely to the environment, and of course this includes differential responses to things like diet and exercise. This is why a personalized approach to health is seductive, and it’s also why we find InsideTracker to be an intriguing solution.
Their platform analyzes your data from blood biomarkers, DNA, and fitness trackers along with your lifestyle and habits to provide guidance that could very well give you greater ROI on your efforts. I haven’t yet tried their solution, but I’m interested to do so, and here is one example of why: LDL cholesterol.
Hundreds of studies demonstrate that concentrations of blood LDL cholesterol can play a causal role in heart disease. We actually have a course on this subject coming soon! Nutrition and other lifestyle factors strongly affect how much LDL you have, however, people eating the same diet can still show variation in LDL levels. Why? Genetics. A number of different genetic variants affect blood lipids, meaning that the same diet will not affect everybody the same way. It’s useful to know if you have a genetic propensity for a health issue but that is not enough. It’s also useful to compare that with blood markers to see if your genetic propensity matches with your current health status (to the degree you can measure it in blood). Combined genetic and blood values could help you lean into an area that you might need to focus on more than others, and this information could very well be useful, if acted upon, for the rest of your life.
Their app also tracks your progress to try to help you assess or focus on what’s working, and continues to adjust based on real-time feedback from your body. I think that is pretty cool. And of course, this applies to lots of different metrics, like blood glucose, vitamin D, etc.
Importantly, this platform has been rigorously tested by scientists. When a group of 1032 individuals used InsideTracker, researchers found that participants were able to improve abnormal biomarkers by using the platform, and that the recommendations provided by the application were associated with said improvements.
They reached out to us and are offering the humanOS audience a 25% discount on their services. We do not get a commission on sales, but we’re delighted to pass this offer on to you. I’m also excited to take part in it myself (Dan).