Background/Purpose: Similar cognitive complaints for patients with fibromyalgia and systemic lupus erythematosus (SLE) have been reported; however, inherently different deficits can share superficial similarities. The major purpose of this study is to determine if the two syndromes have deficits in cognitive functioning in common as measured by the new Mental Clutter Scale.

Methods: The Mental Clutter Scale is a new 16 item scales that focuses on 8 dimensions of the tradition cognitive skills such as memory and concentration, and 8 dimensions of disturbed mental clarity such as cluttered thinking and mental fog.    The measure was administered to 52 patients who met ACR criteria for fibromyalgia and 35 patients who met ACR criteria for Lupus.   The classification criterion for cognitive dysfunction was the upper boundary of the 95% confidence interval (CI) of the normative sample. This score provided prevalence rates of cognitive dysfunction in the two samples.

Results: The two groups were predominantly female (81.5% vs. 82.9%0), with those in the fibromyalgia group significantly older [mean (±SE) age (49.0 ± 12.7 vs. 32.2.3± 10.6 p<0.001)].  Cognitive dysfunction was present in 63.5% (33/52) of the sample with FMS and in 28.6% (10/35) of the sample with Lupus.  The differences were significant (p<0.001).   Both the traditional cognitive symptoms (52.7± 10.0 vs. 32.2± 10.6; p<0.004) and the disturbance in mental clarity (45.5 ± 15.5 vs. 30.6± 10.7; p<0.01) were more pronounced  in fibromyalgia.  Endorsement of the 16 subscales is shown in Table 1.  As can be seen, patients with FMS report significantly higher severity on 5 of 8 cognitive scales, and 7 of 8 mental clarity scales.

Conclusion:   The cognitive findings suggest that there is considerable difference in the cognitive functioning of people with fibromyalgia and Lupus.  The majority of patients with FMS report cognitive dysfunction; whereas only a minority of patients with lupus report cognitive dysfunction.  Among those reporting cognitive dysfunction, cognitive deficits are more pronounced in FMS.  Fog like features as measured by the mental clarity scale are more prominent in fibromyalgia, providing strong support for the notion of fibrofog.  Fog like features play less of a role in lupus, providing weak support for the notion of  brain fog in most lupus patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/cognitive-manifestations-of-fibromyalgia-and-lupus/