Bedtime and metabolic health

Research has shown an association between shift work and metabolic health. Specifically, shift workers are prone to obesity and type 2 diabetes. However, there is less research data about a variable sleep schedule that is not related to shift work. I'm referring to individuals who have one bedtime during the work week but a later bedtime on the weekends. This study researched the effects of going to bed later on weekends and obesity as well as metabolic health. They studied all women with a mean age of 52 years. The researchers collected information annually on sleep times and duration with a sleep diary for about 5 years. They recorded the patient's weight and drew blood to check for insulin resistance (a marker for pre-diabetes). The results showed that a greater variability in bedtime and going to bed early was associated with an elevated body mass index. Interestingly, the mean bedtime and going to bed later were not related to body mass index. However, variability in bedtime and going to bed later on the weekends was associated with an increased rate of insulin resistance, even after adjusting for factors including sleep duration.

The authors speculate on the reason why later weekend bedtimes could contribute to insulin resistance. One possibility is that there is more exposure to light at night which could alter melatonin and possibly increased consumption of food. However there was no significant increase in weight over time despite later bedtime. It may be that people who go to bed later on weekends are eating more simple carbs but don't necessarily gain weight. Increased carb intake could be contributing to the insulin resistance. More studies will need to be done to see how clinically important these effects are, as the statistical differences were real, but small.

Week of camping can reset sleep schedule

Research has shown that our modern lifestyle can make it hard to get to bed early enough. Not just indoor lighting, but the screens from electronic devices used close to bedtime can delay sleep. This article discussed a study about the effects of light on sleep. Researchers took volunteers who normally slept after midnight and 8 am. They had them sleep in tents outdoors for one week with no external lighting of any kind, and no cell phones. After a week, the volunteers had shifted their sleep schedules two hours earlier. Researchers said the participants melatonin levels changed, being secreted earlier.

The headline of this article is misleading, however. The week of camping won't have a lasting affect when the volunteers go back home to their routines. They would have to restructure their time so that their homes are relatively dark and to not use electronic devices close to bed.

Sleep problems common on simulated space mission

Here is an article about an experiment done to simulate space travel. Astronauts were confined to a pressurized spacecraft in Moscow for 520 days straight. Their sleep was monitored with an actigraph, a type of accelerometer. After a month, some of the crew members began to have sleep problems. It seems that one of the issues is that the low light levels on the spacecraft are not strong enough to simulate the day-night cycle we experience daily. Since our brain's clock depends on light to keep our rhythms regular, exposure to stronger light sources on the spaceship may help in actual space flight.

Neuroscientist advises NASA about importance of proper lighting to sleep

This article features a neuroscientist who is advising NASA about replacing its outdated lighting on spacecraft with high tech adjustable lights. This may improve astronauts sleep quality, since light affects sleep and other aspects of our daily functioning.