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‘Neurocognitive’ symptoms, mainly problems with memory and concentration (see review), are extremely common in both ME/CFS and fibromyalgia. Patients usually use the terms ‘brain fog’ or ‘fibrofog’ describe what the experience feels like, and many say that its consequences can be as devastating and as worrisome as the other symptoms, such as pain and fatigue, shared by the two illnesses.

Some fibromyalgia patients become concerned that ‘brain fog’ might be an early symptom of a process leading to Alzheimer’s disease, the most common type of dementia today. For this reason, researchers from Rush Medical College, Chicago decided to look for a decline in cognitive ability in people with fibromyalgia. Using historical data from a repository containing more than 20 years of neuro-psychological information, they identified two groups of women with fibromyalgia: 94 with a short duration of cognitive problems (7.3 months on average), and 55 with longer-lasting cognitive problems (13.3 years on average). Both groups were well-matched as regards educational level, vocabulary scale score and depression – all of which can affect the results of cognitive testing. In total, there were 15 measures of neurocognitive functioning, which rested abilities ranging from word-naming and episodic memory to cognitive effort, sustained attention and mental speed.

Compared with people who had been ill for a short time, long-term fibromyalgia patients showed no evidence of cognitive decline in 14 of the 15 different measures of neurocognition, despite that fact that their cognitive problems had lasted 12.6 years longer. In fact, measures of episodic memory and processing speed (which are good markers of preclinical Alzheimer’s disease) were in the normal range in both groups.

The authors conclude that the brain fog of fibromyalgia (fibrofog) was not associated with progressive cognitive decline. As they explain, “People affected by memory problems for an additional 12.6 years might be expected to display well-advanced cognitive problems, but in reality, they were not significantly more cognitively disabled than those with a history of cognitive problems for 12 months or less.”

Importantly, their findings do not support the idea that there is a transition over time from fibrofog to Alzheimer’s disease. The authors point out that fibromyalgia patients with brain fog remember personal events at a normal rate in quiet, distraction-free conditions, whereas Alzheimer’s disease patients do not. In addition, the inability to appropriately ‘filter out relevant distractions’ is at the heart of memory loss in fibromyalgia, whereas in Alzheimer’s disease the brain mechanisms responsible for fixing events into memory are irreversibly impaired.

The researchers hope that these findings will allay the worries of people with fibromyalgia who fear that their brain fog is the start of a process leading to dementia. There has not yet been a similar investigation in ME/CFS patients but, given the symptomatic overlap between the two illnesses, it would certainly be a worthwhile exercise to undertake.

Reference
Cross-sectional neurocognitive data do not support a transition from fibrofog to Alzheimer disease in fibromyalgia patients. Leavitt, et al. Journal of Clinical Rheumatology, 2015 Mar; 21(2): 81-5. Read more (abstract only).