Blood sugar control and obstructive sleep apnea

Human sleep can be divided into two different stages, non-REM sleep and REM sleep. During REM sleep is when most dreaming occurs. And while we dream, our brain temporarily paralyzes our muscles to minimize potential harm that would occur if we acted out the dreams we had. However, when the throat muscles get paralyzed in REM sleep, the throat becomes even more floppy, and obstructive sleep apnea (OSA) can be more severe. In some patients, the difference in OSA severity from NREM to REM is quite striking - some patients have OSA confined almost exclusively to those periods of REM sleep.

Some sleep researchers feel that OSA confined only to REM sleep may not be as serious as OSA that is present in both stages of sleep, as I have blogged about before. But in my experience, patients that treat their REM sleep-related OSA often have an improved quality of life.

This article showed that the more severe the OSA is in REM sleep, the worse control of diabetes. It's not clear why that would be, but the findings do not support the thinking that REM sleep OSA is less serious. The study authors point out that since most REM sleep occurs in the second half of the night, patients who don't use their CPAP all night may be at greater risk of having less control of their blood sugars.

Weight loss and obstructive sleep apnea

Most people I see already know that obstructive sleep apnea (OSA) is related, at least in part, to elevated weight. Many of my patients start coming to my clinic for help after their OSA symptoms have worsened. Almost all of them report weight gain that occurred as the OSA symptoms worsened. Part of my treatment options, at least for mild to moderate OSA is weight reduction. Easier said than done, however. And if my patient has severe OSA, weight loss alone may not be enough to eliminate their OSA.

This study confirms what I said above. It showed that even moderate weight loss, if maintained, can eliminate mild OSA. The key here is maintaining the weight loss. Many of my patients are able to temporarily drop weight, only to regain it again.

Obstructive sleep apnea and multiple sclerosis

Multiple sclerosis (MS) is a neurological disease thought to be an autoimmune disorder. It causes a variety of symptoms, with a common one being fatigue. Obstructive sleep apnea (OSA) also can cause fatigue. This study sought to examine the relationship between fatigue, MS, and OSA. It was performed at University of Michigan's Neurology Department. MS patients were surveyed about OSA and fatigue. Results showed that 1 out of 5 MS patients reported a diagnosis of OSA. This is higher in the general population. Also, the researchers found that an even higher proportion of MS patients were at risk for having OSA based on a commonly administered questionnaire (the STOP-Bang). Finally, OSA was a predictor of fatigue after adjusting for other clinical and sleep related predictors of fatigue.

What the results mean is that neurologists and other physicians who care for patients with MS should not use the MS as the only reason for a patient's persistent fatigue. OSA could be contributing and the patient may benefit from a sleep evaluation. OSA is treatable and some of the fatigue may improve with OSA therapy.

Obstructive sleep apnea and cardiovascular disease

Research has shown that obstructive sleep apnea (OSA) increases risk of cardiovascular disease - possibly by multiple pathways - repeated oxygen level drop offs, broken up sleep, chronic hyperactivity of central nervous system, and systemic inflammation. However, the studies have looked only at the apnea-hypopnea index (AHI) as a marker for OSA severity. AHI is good for this, as it tells me how many times per hour your airway collapsed, but it does not tell me about oxygen levels or sleep quality. So researchers did this study to address this issue. Specifically, they studied >10,000 people with a wide variety of OSA severity. They examined the relationship between OSA related variables and cardiovascular outcomes as well as all-cause mortality. They even controlled for traditional cardiovascular risk factors like gender, age, body mass index, etc. The results were surprising - the AHI did not correlate with cardiovascular outcomes when controlling for the potential confounders. However, other related variables did correlate - things such as amount of time asleep with oxygen saturations < 90%, the number of awakenings, mean heart rate, total sleep time, and presence of excessive daytime sleepiness. Specifically, the time spent asleep with oxygen saturations less than 90% increased risk of cardiovascular event or death by 50%.