Ever since being diagnosed with Fibromyalgia, Jean Turner has experienced what she refers to as fibro fog.
“I can forget my train of thought in mid-sentence, and often struggle to retain detailed information,” explains the Reading, England, resident. “When I was working-before I had fibromyalgia – I was able to look at my diary on Sunday evening to see what I was doing for the rest of the week and then not refer to it again all week.
“Now, even though everything is written on my calendar in the kitchen, things like appointment times have to be checked several times a day just to make sure I don’t get it wrong. Even that isn’t infallible, though. I still missed an appointment last week!”
Though these cognitive problems are so common among people with fibromyalgia, clinicians don’t always take them seriously and sometimes have a tendency to dismiss them. “If I mention my problems with fibro fog to my doctor,” says Turner, “I know the answer I will get. He will say it’s my age or that everyone seems to be having memory problems these days. But I know it is due to the fibromyalgia.”
The problem is that people with FM tend to perform well in the battery of performance tests that are currently used to measure cognitive difficulties. Patients’ complaints about memory or thinking processes simply don’t match up with the test results, leaving clinicians with the impression that the problems are not as serious as patients make them out to be.
Why is it that people with fibromyalgia perform well in these cognitive tests, but struggle with forgetfulness and brain fog in real life? This apparent puzzle caught the interest of researchers Frank Leavitt, PhD, from the department of psychology and Robert Katz, MD, from the department of rheumatology of Chicago’s Rush Medical College. They have carried out some revealing research into FM and cognitive dysfunction.
“A clue to unravelling the discrepancy between patient conviction of memory loss and normal neuropsychological findings can be gained by highlighting the skills that are assessed by the standard tests used,” Leavitt explains. “A classic example is the Wechsler Memory Scale, generally viewed as the single best measure of memory functioning.”
The Wechsler Memory Scale is a series of memory tests used to assess immediate and delayed recall of verbal and visual information. The problem with this test, in Leavitt’s opinion, is that it doesn’t involve any distraction; participants are able to focus their whole attention on the structured tasks. Leavitt’s research team found that 86 percent of FM participants had essentially normal results using this measure of memory.
“Distraction-free conditions are not representative of difficulties encountered in real life, which is full of stimulus competition that actively divides attention between relevant and distracting information before new information can be rehearsed and stored,” he explains. (“Rehearsing” information refers to the process of repeating it in order to remember it.)
“For example, a clerical employee talking with a customer could be distracted by a phone ringing, by someone speaking in the background, or by the movement of another person walking by. Being able to keep information in mind from a primary task while attending to a secondary task is routine, and absolutely critical to working memory and everyday functioning.”
Leavitt was so convinced about the importance of distraction that, together with Katz, he carried out a research project involving 35 patients with fibromyalgia and 35 patients with complaints of memory loss for other reasons, who acted as the controls’. These 70 participants took part in a series of cognitive performance tests, some involving distraction and some without. What the researchers found was illuminating.
In the tests involving no distraction, only 31.4 percent of the patients with fibromyalgia had significant difficulty with at least one of the tests. When a source of distraction was added, however, 85.7 percent of these FM patients had significant difficulty with at least one of the tests. The most sensitive measure for picking up this difference was the Auditory Consonant Trigram (ACT) test (see box).
When the ACT test was carried out without any distraction, the FM patients essentially performed as well as the control group. But when a distraction lasting nine seconds was introduced, the FM patients lost 58 percent of the new information they were trying to remember. When the distraction time was increased to 18 seconds they lost a total of 74 percent of the new information. In comparison with the controls, the FM patients lost 44 percent more information due to the distractions.
The results clearly show that distraction plays a major role in memory loss in FM patients. “The differences in the impaired rate between the two types of measures [those with distraction and those without] are substantial, and reflect the importance of a source of distraction in assessing memory problems in fibromyalgia,” says Leavitt. “Patients with FM behave essentially normally on the highly structured neuropsychological tests of memory that eliminate distractions. By contrast, adding a source of distraction seriously reduces their ability to remember.
“This inability to filter the effects of distraction may be one reason why new information erodes so quickly in real life situations,” Leavitt continues. “These findings might be taken to indicate that the ability to handle the distractions of daily living may be weakened in FM.”
Turner agrees that distraction affects her greatly. “It really is so easy to lose my train of thought when I’m interrupted,” she says. “If I am asked a question in the middle of what I am saying, I completely lose my train of thought and end up asking ‘Now where was I?’ every time. My grown-up kids tend to think it’s hilarious and often say, ‘Quick, let Mum speak before she forgets what she is saying!”‘
So it appears that patients with FM are not exaggerating the difficulties they experience with memory loss in everyday life; the symptoms are simply not showing up on the usual tests used by neuropsychologists. In this case, it is the tests that are flawed, not the patients’ reports. In a recent U.S. survey, not one neuropsychological test incorporating distraction was listed in the top 50 most popular tests used by neuropsychologists to measure memory. The Auditory Consonant Trigram test was nowhere to be seen.
“The sad reality is that the wrong tests are being applied in examining fibromyalgia patients with cognitive complaints,” says Leavitt. “In the recent U.S. survey of neuropsychological measures, the measure most widely used by neuropsychologists to assess memory function in fibromyalgia was the Wechsler Memory Scale. Unfortunately, it is also a measure with serious shortcomings for assessing memory complaints in FM, as it entirely eliminates sources of distraction. Instead, it taps cognitive skills that are largely working adequately in FM, and obscures the cognitive deficiencies that are salient to their complaints.
“People can have excellent memory when isolated in a distraction-free environment, and extremely poor memory when they must deal with a source of distraction that divides their attention,” he continues. “We believe that detection of cognitive deficiency in FM is simple, but is hampered by the poor diagnostic accuracy of conventional tests.”
Recently Leavitt and Katz rediscovered the Stroop test (see box on page 39), which distinctly reveals abnormal cognitive processing in fibromyalgia compared to other patients with complaints of memory loss. They decided to measure processing speed with a series of 10 timed tests involving the processing of letters, numbers, words, symbols, and colors2 They found that compared with other patients with complaints of memory loss (controls), the majority of the patients with FM performed better than the controls on eight of the timed tasks, but were slower at reading words and naming colors. In fact, 50 percent of the FM patients were twice as slow at reading and 1.6 times slower at naming colors.
People without memory or processing problems read words at a rate of 108 words per45 seconds, or417 milliseconds (ms) per word, and name 80 colors in 45 seconds, or 562 ms per color. The impaired FM patients took 620 ms per word and 847 ms per color, which is a delay of 203 ms per word and 285 ms per color. Essentially, the FM patients are doing the same job at roughly half the speed.
So why do Fibromyalgia patients struggle with reading words and naming colors, but perform adequately in other speed processing tests involving numbers and symbols? One explanation is that different mental processes in the brain are flowing at different speeds. For example, naming words involves the part of the brain that processes letters of the alphabet, and turns what you see and understand into spoken language.
This part of the brain is referred to as the lexicon, the vocabulary storehouse of a language. Its job is to name and assign meaning to sequences of letters based on the vocabulary built up through years of experience in processing words. It is possible that FM patients may experience delays in accessing lexical information, but are able to the process numbers and symbols at normal speed.
This extra processing time required to access lexical information not only slows down the activity of reading, it also reduces the ability to remember what you have read. Leavitt explains: “If increased time is needed to access the stock of lexical traces [information], it slows the flow of information and diminishes the time available for processing the information. It is as though a 203 ms-time delay is put on the information entering the short-term memory bank of individuals with fibromyalgia, thus shortening the time to lay down a strong memory trace by 203 ms.”
The presumption is that because the slower flow of information shortens the processing time, people with FM tend to create weaker memory traces. The weaker the memory traces, the less likely you are to remember what you have read.
If you add in a source of distraction, it makes the situation even worse. Distraction prevents any chance of solidifying the weak memory traces. Usually, you would naturally rehearse the information to reinforce it, making the memory trace stronger. The lack of rehearsal and reinforcement due to the distraction makes the memory traces fade faster than normal, making it difficult to retrieve the information. No wonder people with FM struggle to remember things!
Leavitt’s and Katz’s discovery-that tests involving distraction and naming can specifically reveal the cognitive difficulties experienced by people with FM-offers clinicians an opportunity to identify and confirm the cognitive symptoms that FM patients are reporting. Leavitt and Katz believe they may even point towards the underlying neural mechanisms involved in fibromyalgia. So if you ever have the opportunity to have your cognitive symptoms tested you know which tests to request!