Many researchers have shown that people with fibromyalgia (FM) have an autonomic nervous system with a hyperactive sympathetic branch and an underactive parasympathetic branch. The sympathetic system is geared to respond to stress, but who needs this system to be on full throttle when one is sleeping? The parasympathetic system is designed to aid with sleep and digestion, but obviously it’s not doing an adequate job because sleep is severely disturbed and digestion is slowed (see results in section above).
Ordinarily, the sympathetic system is dominant during the day and the parasympathetic system is dominant during the night period. Although previous studies have shown sympathetic dominance, a research team from Turkey was interested in measuring the day-to-night fluctuations in the autonomic system and whether patients were more prone to cardiac arrhythmias.* In general, a cardiac arrhythmia is an alteration in the heartbeat caused by abnormal neurological impulses traveling to the heart muscle. The heart, as with all other organs, is controlled by the autonomic nervous system.
Fifty FM patients and age-matched healthy controls were studied with a small 24-hour heart monitor to evaluate the autonomic nervous system function during the day and night. Subjects were also put through a number of tests to assess how their autonomic and cardiovascular systems responded to abruptly laying down to standing up (and vice versa).
FM patients were clearly different from the healthy control group in many ways. The nighttime sympathetic activity for the FM group was just as active as it was during the day and the parasympathetic system never did step up to the plate, activity wise. This means that during the night when you are trying to sleep, the stress response branch of your sympathetic system is revved up for action. Naturally, this situation is not at all conducive for sleep and could explain your nighttime troubles. An active sympathetic system is not going to allow you to easily drift off into deep sleep and will likely limit your ability to stay asleep, particularly the deep stages that restore your body.
When FM patients went from standing to laying down, or vice versa, the difference in autonomic function between the patients and healthy control subjects was more exaggerated than the findings between night and day. After laying down, the sympathetic system continued to be dominant. Upon standing, the sympathetic activity in the FM group did not change because it was already operating at maximum capacity and was unable to respond to the stress challenge of standing up. This may help explain why so many FM patients in the above COMPASS study stated that they felt dizzy or faint when they stood up because this activity requires the sympathetic system to quickly activate the heart to pump more blood to the head. In FM patients, the sympathetic system is maxed out and cannot respond to even simple challenges such as going from a reclined to standing position.
If the autonomic nervous system that controls the heart is not functioning properly in FM patients, could this impact their odds of cardiac arrhythmias? The Turkish team found that the answer to this question was “yes” —but only by a small factor. Although more studies are warranted to determine how the abnormalities seen in the autonomic nervous system might contribute to increased incidence of irregular heart patterns, or cardiac arrhythmias, the research team concluded that FM patients should be closely followed for arrhythmias.
Before you overreact, please keep in mind that arrhythmias do occur in healthy people and may not be serious in nature (do not rush to your doctor to ask for a cardiac workup). Also, the majority of the arrhythmias were detected during the nighttime, so standard daytime EKG tests that are often used to evaluate heart function may not pick up arrhythmias. However, if you do notice a lot of irregular heartbeats, particularly skipping of a beat, you may require a 24-hour holter monitor or a device called an event monitor to pick the cardiac irregularities. Keep in mind that cardiac workups can be extremely costly and may not lead anywhere in terms of treatment.
The best way to use the findings from this study is to better understand your symptoms, such as your difficulty sleeping (review the suggestions offered in the April 2009 Fibromyalgia Network Journal for how to turn off the chatter in your brain during the night). Also try to eliminate as much stress from your life as possible. Stress does not cause FM, but nonetheless, your body does not respond properly to stress. And keep in mind, future research on the role of the autonomic nervous system in FM is bound to bring forth more answers about the many symptoms that bug you.
* Dogru MT, et al. Anadolu Kardiyol Derg 9(2):110-7, 2009