Wednesday, November 27, 2013

Workweek sleep restriction and weekend make up sleep

Here is an interesting study about the effect of mild sleep restriction and make up sleep. In this study, researchers took young, healthy volunteers and had them restrict their sleep from 8 hours down to 6 hours for 6 nights in a row. Then they let them sleep upto 10 hrs per night for 3 nights. During this study, they measured blood markers of inflammation, sleepiness, and performance with a computerized test.

The results showed that cortisol levels did not change with sleep restriction, but did fall below baseline after the recovery sleep. This is interesting to me on two fronts. One is that sleep deprivation did not raise cortisol levels. More interesting was the effect of recovery sleep on lowering cortisol from the baseline. I assume it's the relatively increased amount of deep sleep obtained during recovery that played a role in lowering cortisol levels.

Another marker for inflammation, interleukin-6, did increase during sleep restriction and fell back to baseline with recovery sleep. And subjective and objective sleepiness increased after restriction but returned to baseline after recovery. However, performance deteriorated significantly after restriction and did not improve completely after recovery. And this was after just one week of restriction. It will be interesting to see long term studies that would replicate this week after week, like what many working people do. Would performance continue to decline and not fully recover on weekends? Or would acclimation happen, such that performance level decrements stopped or where recovery sleep became better at improving performance?

Wednesday, November 20, 2013

Drowsy driving

This article discusses a survey about driving while sleepy. Lots of drivers still do it. The survey showed more than a quarter of respondents admitted to drowsy driving in past 30 days. This was more common in young drivers. Perhaps it's because more young drivers take risks and are more likely to stay up later. Drowsy driving is a serious problem. If you are sleepy, do not drive. If you get sleepy while driving, you should pull over to a save location and take a brief nap. Or if you are driving with someone else, switch drivers.

Wednesday, November 13, 2013

Poor sleep quality and Alzheimer's disease

This article discussed research about Alzheimer's disease and sleep. Researchers looked at a marker for Alzheimer's, called beta-Amyloid. The results showed that those with lower sleep quality and shorter sleep duration had higher levels of beta-Amyloid. However, sleep duration and quality was determined by subject self-report. It will be helpful to see if the relationship holds up with objective sleep measurements.

Wednesday, November 6, 2013

Obstructive sleep apnea and cardiovascular disease

Obstructive sleep apnea (OSA) is associated with elevated risk of cardiovascular disease. However, it's been difficult to show a causal link because OSA occurs so commonly with other risk factors, like obesity and high blood pressure. This article discusses research showing that OSA is independently associated with a marker (troponin) for heart muscle injury. The more severe the OSA, the higher the level of this marker. And the relationship held true after adjusting for 17 other variables.