The Hidden Cause of Fatigue, Hypertension, High Cholesterol, and Diabetes

Dr. Frank Shallenberger, MD

May 6, 2019



Anita had a bad problem. She was tired every day; often to the point of complete exhaustion. She had been this way for several years, and now it seemed that there was no relief in sight.

At first her doctors thought it was just because of her age. After all, she was 64 years old. And all of her blood tests were normal. But the problem just kept getting worse.

After two years of this, Anita had another complete physical examination, along with all the standard blood tests. Her blood pressure was slightly elevated. So were her blood sugar and cholesterol levels. But her doctor couldn’t find anything to account for her fatigue. He was stumped. So he sent her home with a prescription for a blood pressure pill, but admitted it wouldn’t help her feel better.

Then something happened that broke the case apart. She passed out. She was just standing in the kitchen when she suddenly and without warning passed out. Her husband immediately called the paramedics.

In the emergency room, a very astute emergency room doctor told her that he knew what had been causing not only her fatigue, but also her elevated blood pressure, cholesterol, and blood sugar. He thought she had sleep apnea.

Now Anita was not typical of most people with sleep apnea. She wasn’t overweight, and she didn’t snore. But the emergency doctor insisted that her symptoms indicated sleep apnea.

The Most Common Kind

Because it is so common, you probably know a lot about sleep apnea already. More than four million Americans have it. People with sleep apnea literally stop breathing during their sleep. This may happen as many as hundreds of times during a single night. And each episode may be as long as a minute or even longer.

There are three different forms of sleep apnea: obstructive sleep apnea (OSA), central sleep apnea (CSA), and complex sleep apnea. Complex is a combination of central and obstructive. OSA is the most common kind. Statistics show that it accounts for about 84% of all cases.

In OSA, the reason that breathing stops is that the airflow through the upper airway becomes obstructed or blocked.

CSA is completely different than OSA. There is no obstruction. It’s simply a problem with how the brain controls breathing during sleep. For reasons that are not usually obvious, the brain stops sending the proper signals to the muscles that control breathing. It is often triggered by taking alcohol, sedatives, or sleeping pills before bed. It can also be caused by other medications, especially the combined effect of several different medications. And lastly, it can be a side effect of a serious illness, such as encephalitis or a neurodegenerative illness like Parkinson's.

A Deadly Condition

Whether you have OSA or CSA (or both) the final result is the same – the brain is starved of oxygen during sleep. But most people don’t realize just how damaging that is. When the brain doesn’t get enough oxygen, it’s not able to enter into the deeper, restorative stages of sleep that are so important for health.

Additionally, many studies indicate that each apneic event causes a “fight or flight” reaction in the body. This causes harmful hormonal imbalances, such as excessive adrenalin and cortisol production. Those changes, coupled with the low oxygen saturation level of the blood, can cause significant damage — even disease — to the body over time.

A Better Test — And It’s Free!

Most data you’ll read about CSA say it’s rare, less than one out of every 200 cases of sleep apnea. But I think that’s mostly because it’s under-diagnosed. Under-diagnosed for two reasons.

First, because doctors and patients usually don’t think of it. Everyone knows about the symptoms associated with OSA, such as weight gain and snoring. But CSA can occur without these symptoms.

Second, many doctors think that the only way to diagnose sleep apnea is in an overnight sleep lab. Overnight sleep labs are very expensive, often costing from $4,500-$6,000 per test. That makes it out of reach for many people. There’s no doubt that overnight sleep studies are the most comprehensive evaluation for sleep disorders. But in many cases, they are not needed. There’s another way to diagnose both CSA and OSA that does not require a night spent in a sleep lab — or the extreme expense. The test is overnight home oximetry. Researchers recently documented the effectiveness of overnight home oximetry.

Overnight home oximetry is so easy to do. All it involves is wearing a small clip called an oximeter that fits over the end of one of your fingers. You put it on before you go to sleep and take it off the next morning. A small wire connects the oximeter to a recording device that continuously monitors and records the level of oxygen in your tissues during the night. The next morning, it prints out the minute-by-minute results, graphed and analyzed.

Researchers recently documented the effectiveness of overnight home oximetry. In this study, researchers evaluated 68 patients for sleep apnea. All of them had symptoms of sleep apnea, as well as elevated Epworth Sleepiness scores. All of their doctors considered them to be “highly likely” to have sleep apnea. And half of the participants had this confirmed using an overnight study in a sleep lab. The other half used only overnight home oximetry. The researchers found that overnight home oximetry is just as accurate and easier to obtain than a formal sleep lab study.

But the best part about overnight home oximetry is that most oxygen supply companies will provide it free of charge! And this means that doctors can easily screen for apnea in virtually everyone they suspect of having the problem. I have been able to diagnose all three kinds of sleep apnea many times simply with a free overnight home oximetry. And I believe that CSA would not be considered so rare if more doctors used this test.

Of course, the treatment most doctors prescribe for sleep apnea is the C-PAP. But there are a lot of reasons most people don’t want to use these machines. Fortunately, there are alternatives. I’ll tell you about those next week.


Mulgrew AT, Fox N, Ayas NT, Ryan CF. Diagnosis and initial management of obstructive sleep apnea without polysomnography: a randomized validation study. Ann. Intern. Med. 146 (3): 157-66.

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