Cognitive dysfunction is a signature feature of fibromyalgia. Many who develop cognitive problems in their middle years are concerned that it is prodromal to Alzheimer's disease.
To determine if deficits in episodic memory and progressive cognitive decline, hallmarks of Alzheimer's disease, are prominent in the cognitive makeup of fibromyalgia patients.
In a cross-sectional study, performance on 15 neurocognitive (NC) measures was evaluated in 2 cohorts of fibromyalgia subjects. The first cohort contained 94 subjects with a short duration of cognitive problems (≤12 months). The second cohort contained 55 subjects with a long duration of cognitive problems (≥84 months).
The 2 groups were similar in education (14.9 ± 2.3 vs 14.9 ± 2.4), vocabulary scale score (11.2 ± 2.3 vs 11.6 ± 2.7), and depression (17.9 ± 9.8 vs 17.7 ± 9.4). The mean durations of cognitive problems in the short- and long-term group were 7.3 ± 3.9 months and 13.3 ± 7.1 years, respectively. There was no evidence of decline on 14 of 15 measures in the fibromyalgia group with an additional 12.6 years of cognitive dysfunction. Normality of function was in evidence on 4 measures of episodic memory in both cohorts.
Fibromyalgia patients' fear of developing Alzheimer's disease was not borne out by the data. The cognitive pattern of fibromyalgia appears distinct from that of Alzheimer's disease. Fibrofog is not associated with either episodic memory loss on standard tests of episodic memory or progressive cognitive decline. Patients with fibrofog remember personally experienced events termed episodic memory at a normal rate in quiet, distraction-free conditions. Patients with Alzheimer's disease do not. They forget the essential elements of short stories just read to them in environments free of distractions. In Alzheimer's disease, the brain mechanisms responsible for encoding personally experienced events into memory are irreversibly impaired. In fibrofog, the encoding mechanisms are intact. At the heart of memory loss in fibromyalgia is the inability to appropriately filter out relevant distractions. Encoding mechanisms that otherwise operate normally in forming episodic memories for everyday events in fibromyalgia appear to malfunction when 2 streams of information operate concurrently (relevant information and a source of distraction overlap). The findings should allay the worries of many with fibromyalgia who fear that fibrofog is the start of a dementing process.