There are different types of mental and cognitive changes, and some are worse than others. Patients with FMS who reported a combination of memory decline and mental confusion reported they perceived their illness to be of greater severity – more pain, stiffness, fatigue and disturbed sleep, compared with patients reporting just memory problems alone. In general, for patients with FMS, peak cognitive performance tends to occur only during a limited time during the day, approximately 10 am to 2 pm. Sound familiar?
A group of FMS patients were brought together in focus groups and asked to tell researches specifically about their FMS problems. When patients are asked about the effects FMS had on their thinking they reported concentration and memory difficulties that affected their ability to organize, plan, and express themselves especially because of an inability to find words. How many times has this been your problem?

Given the impact reported by patients only one study, published in 2005, has used a well-validated cognitive function questionnaire. This is important in the scientific world because it means not only that the results will apply to individuals other than just those studied in the experiment but the questionnaire has something called scientific validity, meaning it seems to be free from biases that may affect how well it measures what it is designed to measure.  Their findings demonstrated lower memory capacity, more memory deterioration, and higher anxiety about memory among FMS patients than age matched people who did not have FMS.

There are three categories of memory that may be independently affected – semantic, episodic, and working memory. Semantic memory involves stored knowledge and facts (your mother’s birthday), episodic refers to the ability to remember past specific individual events or episodes (the location of your honeymoon), and working memory concerns short-term storage of information for brief periods of time, e.g. seconds (the phone number you never heard before your friend wants you to call).

One study that was published in 2001 found evidence of cognitive dysfunction in patients with FMS that was related to just pain levels and did not seem to be affected by psychological or psychiatric conditions. In this study the greatest impairment was seen in working memory followed by episodic memory. Since that review, a number of other studies have provided even greater insight.

Another study found that FMS patients’ performance in working memory was similar to control subjects 20 years older than they were – someone with FMS who was 40 had the working memory of someone who was 60!  This study also found deficits in free recall, verbal fluency, and vocabulary which are measures of semantic memory. FMS patients in this study showed impaired cognitive performance that correlated with pain complaints, but were not affected by any depressive or anxiety symptoms they  may have had.
An unappreciated feature of the cognitive disturbances of FMS is abnormalities of naming speed, another feature of semantic memory. In naming speed, someone is asked to say all the words they can think of that begin with one letter, say the letter “a.” You can try this yourself. Look at your watch, and then count all the words you can think of that begin with the letter, “a” for the next 45 seconds. It’s actually more difficult than you think. You’ll be surprised at how quickly you run out of words. Then try the test with someone who doesn’t have FMS.

More than 49% of FMS patients tested in one study were impaired on two validated speed tasks, reading words and naming colours. This indicates a deficit in accessing stored knowledge.  This is also what was related by both the patient focus groups and the clinical domains that were identified in the Delphi exercises;  patients said they had word finding difficulties.  Researchers in one study have actually quantitated the delay in naming words, which is approximately equal to the delay at which information enters short term memory banks, at 203 milliseconds. In this study, FMS patients were also found to have mild deficits in episodic memory, but not as significant as those with working memory.  

The problems FMS patients have with working memory may be more due to the “management” of the contents of working memory than an actual loss of storage capacity. As an analogy, your computer has a large hard drive but not enough RAM. Given this condition, an important environmental variable is distraction. Results from several separate types of attention tests suggest that a particular problem with FMS patients is dealing with distraction or focusing on the material at hand.  When a source of distraction was added to a standard memory task FMS patients lost new verbal information 44% faster than an age matched control group that also had their own memory problems and almost three times faster than a normal group. Without the distraction, short term memory in the FMS patients was normal.

The element of distraction is unique to patients with FMS especially in regard to psychological testing. If any of you have had this type of testing think about where it was done – probably a quiet room. This type of testing is almost always done in a quiet setting without any source of distraction. For example, if an individual with FMS is being given psychological tests to assess their job performance, their ability to perform a job, or even be considered for disability, an important consideration is the degree of distractibility present on the job. A psychological examination completed without distractions in a FMS patient could potentially miss abnormalities in memory. If their work environment provides considerable distractions and does not allow the individual to attend to their job there would be little correlation to a psychological test done without some type of artificial distraction. Most FMS patients do not differ from age matched people without FMS in their ability to lay down new memories provided they are free of distractions.  

With the scientific findings as of 2009, two FMS researchers propose that “fibrofog” results from the recurring 203 millisecond time lags of sensory information entering and leaving the short-term memory banks adding up over millions of times a day combined with additional disruptions from outside distractions that together affect the how the brain processes information.  They suggest one way to manage this condition, at least the difficulties created by distraction, is by someone with FMS adding a “rehearsal of information.” In other words, repeating to themselves the information they need to know. This can partially compensate for the losses due to processing time and create a memory that is less affected by distraction.

Sleep and pain would be expected to have effects on cognition. The first effects of sleep on cognitive performance were published in 1997 Dr. Moldofsky and another researcher. You can read more about Dr. Moldofsky in the short report that deals with FMS and sleep. One researcher has investigated the disruption of cognitive function in patients with FMS and found little differences when controlling for self-reported pain but significant differences remaining when controlling for sleep, anxiety, or depression.  In general, the studies suggest that although disrupted sleep contributes to dyscognition it cannot account fully for its full effects.

Several studies have shown a correlation between patients’ self-reported pain levels and cognitive performance. This is not an unexpected finding given that pain would distract anyone from paying full attention to normal activities. Past studies on chronic pain syndromes have shown that chronic pain recruits brain regions involved in emotional processing and decision making that would normally be involved in cognitive processes.  Given that pain and perceived distress is significantly higher in FMS patients than other pain conditions this is a relevant issue.  Consequently, the “attentional cost” of pain makes less brain “resources” available for information processing.

The studies mentioned above have primarily concentrated on memory processes but four studies have shown that patients with FMS can also have deficits in executive functioning as well. Executive functioning is a term that refers to the higher process of brain function, for example, doing your tax return. One study comparing FMS patients with chronic pain patients and healthy controls did not show any differences in executive function after controlling for fatigue, pain, and depression although depression was related to memory performance and fatigue to psychomotor speed.  Psychomotor speed is simply how fast your brain processes information, similar to how different microprocessors make better computers run faster.

There are specific, measurable and objective cognitive impairments in patients with FMS. However, the subtleties of this patient population, for example, the effects of distraction, render detection difficult for standard neuro-psychological tests that assess more complex functions. One way that researchers have surmounted this problem and gained insight into these processes has been through fancy neuro-imaging techniques such as functional magnetic resonance imaging and positron emission tomography. These are going to be the topics of future short reports so that you can gain an even better picture of “your brain on fibromyalgia.”