Wednesday, October 29, 2014

Tongue fat and sleep apnea

Apparently your tongue is fat. I mean that there is a normal amount of fat within your tongue muscle. And if you have obstructive sleep apnea (OSA), you may have too much tongue fat. At least according to this recent study. Researchers used sophisticated MRI scans to compare the overall volume and amount of fat in the tongues of overweight men with and without OSA. The results showed that the more obese the subject, the larger the tongue and the higher amount of fat in the tongue. There was also a significant association between belly fat and tongue fat. Patients with OSA had more tongue fat than in the control patients. They also had higher tongue volumes and a higher percentage of tongue fat. There was also an association between the sleep apnea severity and the tongue volume as well as amount of tongue fat.

The amount of fat was greatest in the back of the tongue rather than the front of the tongue in the patients with OSA. This makes sense anatomically because the back of the tongue is involved in blocking off the upper airway during sleep apnea. Another interesting finding was that the researchers examined the chewing muscle and it did not have a higher percentage of fat. This means that when patient's have extra weight, it's not deposited uniformly in the neck and head, but only in certain areas.

Finally, the researchers suggest that the increased amount of fat in the tongue in those with OSA can inhibit the way the tongue normally moves out of the way to allow air to flow.

Wednesday, October 22, 2014

Salt water infusion and sleep apnea

Sleep researchers have not worked out exactly how we develop obstructive sleep apnea (OSA). There are several risk factors and anatomical reasons involved. Some researchers have postulated that OSA may be worsened by fluid shifting from the legs to the neck area overnight. In other words, because the legs are generally at the level of the heart while in bed, fluid from the legs moves into the neck area, causing swelling in the upper airway. This narrows the upper airway enough to restrict airflow.

In this article in the Journal Sleep, researchers studied older and younger men to see if giving them IV salt water impacted the level of sleep apnea. The study was limited to men who were not obese and had either no or non-severe OSA. They did sleep studies after giving them the IV salt water. The results showed that the IV salt water worsened OSA significantly in older men, but not younger men. The reason for this was not clear from the study. However, the results have important implications for older men undergoing surgery, since IV fluids are commonly given during and right after surgery.

Wednesday, October 15, 2014

Hibernation to reduce the cost of manned space flights

Here is a fascinating article about space travel. Apparently, a trip to Mars will take about 6 months. A team at NASA has shown that putting astronauts in a form of hibernation can significantly reduce the cost of a trip, as much less food will need to be brought if the crew is hibernating.

The way it works is that the crew members will be cooled down to 89°F – 93°F by fluid pumped through their noses! The crew will be fed intravenously while they hibernate. The article does not mention how urination is dealt with - catheter maybe? When the crew arrives at Mars, they will be warmed up again and woken up. The article mentions that during hibernation, the crew will be in a "spinning habitat...to offset bone and muscle loss." Sounds like something out of a science fiction movie, only apparently it's very possible to do this now.

Wednesday, October 8, 2014

Rising prevalence of obstructive sleep apnea

Obstructive sleep apnea (OSA) is becoming more common in the U.S. When I was a sleep disorders fellow, it was thought that OSA occurred in 2% of women and 4% of men. This article highlights how the rates of OSA have increased in the past two decades. Apparently, OSA now is present in at least 25 million adults in the U.S. and in 26% of adults between the ages of 30 and 70 years old.

The article discusses the complications of untreated OSA too. It does not discuss why the prevalence rates have risen. I suspect more public awareness of the symptoms, more acceptable treatment options, rising obesity rates, and aging population contribute to the increase in OSA rates.

Wednesday, October 1, 2014

Deep sleep circuit in the brain

There are 4 different sleep stages that humans cycle through at night. Deep sleep is one of those stages, and is typically seen in the first half of the night, at least in adults. Sleep researchers do not know exactly how deep sleep is produced, but it's thought to involve the neurotransmitter GABA, which stands for gamma-aminobutyric acid.

Here is a report of a study involving stimulation of a deep part of the brain (the brainstem) that turns on deep sleep. The technique used to stimulate this area of the brain is different than other methods involving electrical stimulation of the cells in the brainstem felt to be responsible for deep sleep. With electrical stimulation, the problem is that the electrode stimulates everything it touches, including surrounding areas it did not come into contact with. As stated in the article, electrically stimulating cells was like using a sledgehammer, when what was needed was a scalpel. In this study, researchers inserted a harmless virus that incorporated itself precisely into the very cells the researchers were trying to study. The cells were then remotely "turned on" and the animals went right into deep sleep.

This is exciting research as it points to the possibility of developing therapies that enhance deep sleep by targeting only certain brain areas. Hopefully this will lead to treatments with more specific modes of action and less side effects.

Wednesday, September 24, 2014

Insomnia and obstructive sleep apnea

I've followed Dr. Barry Krakow's work for years, starting when I was a fellow at Dartmouth. Dr. Krakow is an expert on insomnia, nightmare treatments, and obstructive sleep apnea (OSA). I have a copy of one of his insomnia books, called Sound Sleep, Sound Mind, and I recommend it highly. Besides treating nightmares, Dr. Krakow has brought to the mainstream the common co-existence of insomnia and OSA, and the relationship to each other. Now, he has published an exciting paper in the Mayo Clinic Proceedings, but I don't have access to it - all I have is the abstract.

In this study, Dr. Krakow evaluated over 1200 patients with chronic insomnia. Almost three-fourths of the insomnia patients did not respond to medications for their insomnia. Dr. Krakow studied 942 of them in the sleep lab using the most modern testing equipment, not done in older insomnia studies. Results showed that over 90% of these patients had moderate to severe OSA! The results are somewhat surprising with respect to the percentage of insomnia patients that had undiagnosed OSA. In my clinic, I regularly get patients referred to me for "insomnia" that actually have OSA, and sometimes it is severe. In these cases, treating the OSA usually improves sleep quality significantly such that sleeping pills are no longer needed.

The bottom line is that patients with chronic insomnia that do not respond to medications may benefit from referral to a sleep specialist for evaluation of underlying medical causes of the insomnia, such as OSA.

Wednesday, September 17, 2014

Brain changes before and after CPAP treatment for obstructive sleep apnea

Some studies have shown changes in the white and gray matter of the brain from untreated obstructive sleep apnea (OSA). The gray matter refers to cell bodies in the brain and is generally on the outer surface. White matter is the connections between the cell bodies and some of the supporting cell types - it's deeper in the brain, meaning below the gray matter.

This study sought to evaluate white matter changes and impact on cognition in patients with OSA, and if the changes were reversible with CPAP therapy. The researchers studied 17 patients with severe OSA and compared them to similar patients that did not have OSA. The treated patients were evaluated at baseline, 3 months, and at 12 months - however, the controls were only evaluated at baseline. CPAP use was monitored objectively with downloads from each unit.

Results showed changes in white matter in the untreated OSA patients. There was only limited improvement with 3 months of CPAP, but there was significant improvement at 12 months of CPAP. This is an exciting study because it suggests that the brain damage inflicted by untreated severe OSA may be reversible with regular, prolonged CPAP treatment.