Metrics, Sleep

Studies on Sleep that Validate our Variance Metrics Tool

Surveying information this week I came across two quick studies highlighting two different data collection points in our variance metrics tool.

Time eating before bed

This is an oft-overlooked facet of our daily environmental signaling. As described in the page explaining the metric tool, going to bed on a full stomach can disrupt sleep which will obviously lead to a lesser state of well being the next day. This study shows in specificity one way in which eating in close proximity to bed may cause metabolic dysfunction.

These results suggest that moving the dinner to an earlier time may result in better glucose tolerance especially in MTNR1B carriers.

Even though the study was flushing out a specific genetic presentation, it is useful to see this facet of late night eating manifest in impaired insulin resistance which can, of course, lead to diabetes as well.  This concept of avoiding meals during ramp up to melatonin rise has also been documented in a terrific new book:

as melatonin levels begin to rise 2 to 4 hours before your typical sleep time. Finishing your meals before melatonin begins to rise is necessary to escape the interfering effect of melatonin on blood sugar. 

Satchin Panda, The Circadian Code: Lose Weight, Supercharge Your Energy, and Transform Your Health from Morning to Midnight, loc. 1671 

The other study that showed this interval was impactful is titled Early supper associated with lower risk of breast and prostate cancer

Having an early supper or leaving an interval of at least two hours before going to bed are both associated with a lower risk of breast and prostate cancer. Specifically, people who take their evening meal before 9 pm or wait at least two hours before going to sleep have an approximate 20% lower risk of those types of cancer compared to people who have supper after 10pm or those who eat and go to bed very close afterwards, respectively.

Light Intensity Exposure

Another collection point we gather is the number of hours of bright vs less bright you are exposed to during the day and contrast that to your evening hours of dim light exposure. It is been written about much that blue light exposure in the evening causes suppression of melatonin and can decrease sleep quality. This study looked at if the evening low light exposure was as important if one gets sufficient bright daylight exposure.

Methods: Followingaconstantbrightlightexposureover6.5hours(~569lux),14participants(six females) read a novel either on a tablet or as physical book for two hours (21:00–23:00). Evening concentrations of saliva melatonin were repeatedly measured. Sleep (23:15–07:15) was recorded by polysomnography. Sleepiness was assessed before and after nocturnal sleep. About one week later, experiments were re- peated; participants who had read the novel on a tablet in the first experimental session continued reading the same novel in the physical book, and vice versa. 

Results: There were no differences in sleep parameters and pre-sleep saliva melatonin levels between the tablet reading and physical book reading conditions.
Conclusions: Bright light exposure during daytime has previously been shown to abolish the inhibitory effects of evening light stimulus on melatonin secretion. Our results could therefore suggest that expo- sure to bright light during the day – as in the present study – may help combat sleep disturbances associated with the evening use of electronic devices emitting blue light. However, this needs to be validated by future studies with larger sample populations. 

When developing the algorithm that computes the various scores, the one that got the biggest numbers was always the light section. I continued to scrutinize closely because I was unsure if spending 2+ hours in the sun with no sunglasses warranted super high scores. This data certainly validates what we are measuring. The appropriately timed bright daylight exposure essentially downplayed the brighter pre-bed light exposure. They looked at 500 lux which is essentially like a hospital or an overly bright retail environment like a big box retailer. Most office workers are getting far less than that though, so if you aren’t getting your outside light, even cloudy days are often much greater than 500 lux, so the evening light sleep disruption can still persist.

These were two validations of our data collection points that I came across this week. Head over and start collecting today to see how different environmental exposures each day impact how you feel and perform.

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