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.

Sleep deprivation and fat cell insulin resistance

This article discusses research about the effect of sleep deprivation on fat cells. They studied young, healthy people - allowing some to sleep only 4.5 hours per night and the other to sleep 8 hours for a few days. They examined each groups fat cells and determined that the short sleepers had more resistance to insulin. They concluded that sleep deprivation may impair our fat cells' ability to respond to insulin, which may lead to diabetes.

These findings are interesting, but there are some problems with the conclusions, as pointed out in the article. For example, most people do not get only 4.5 hours per night, more like 6 hours. Do they have the same effect. Also, most do not deprive for only a few days, but for months / years. Does our body adapt and do the fat cells than have normal insulin sensitivity? More research is definitely needed.

Obstructive sleep apnea is linked to decreased insulin resistance.

This article describes research showing that children with obstructive sleep apnea have decreased sensitivity to insulin. Decreased sensitivity to insulin can be seen in diabetes. The researchers hypothesized that oxygen level decreases seen in obstructive sleep apnea could be responsible for the decreased sensitivity to insulin. Results of this study suggest that it is important to screen patients with diabetes or who are prediabetic for obstructive sleep apnea.

Insomnia, obstructive sleep apnea, or daytime sleepiness is linked to insulin resistance

This article discusses research showing that patients with insomnia, obstructive sleep apnea (OSA), or excessive daytime sleepiness are more likely to have insulin resistance. This is no surprise to me, as research has shown a link between OSA and diabetes before. But this research may prompt primary care physicians to test their patients for diabetes if they also experience insomnia or daytime sleepiness, or have known OSA.