Background: Fibromyalgia (FM) is a prevalent disorder estimated to affect 2-6.4% of the United States adult population (more than 5 million Americans).[1, 2] While chronic widespread pain is a fundamental symptom of FM, cognitive impairment is also a core manifestation, colloquially referred to as “fibrofog”, and may be even more disabling than pain symptoms. Studies report that 50-80% of FM patients experience memory decline, mental confusion, and concentration difficulties. There is limited data exploring risk factors for cognitive dysfunction in FM patients. The objective of our study is to evaluate the association between smoking and cognitive function in patients with FM.
Patients and methods: We surveyed 668 patients with FM from May 2012 through November 2013. Informed consent was obtained by all participants and our study was approved by our hospital’s Institutional Review Board. Patients were categorized by smoking status (non-smoker and smoker). Primary outcome of interest was cognitive function (MASQ), and secondary outcomes included FM symptom severity (FIQ-R), quality of life (SF-36), fatigue (MFI-20), sleep (MOS-sleep scale), anxiety (GAD-7), and depression (PHQ-9). Independent t-tests and Chi-square tests were performed for continuous and categorical variables, respectively. Univariate multivariable regression analysis was performed to identify if smoking was predictive of primary and secondary outcomes.
Result: Ninety-four (14.07%) patients self-identified as smokers. There was an association of lower education level (p<0.001), unmarried status (p<0.001), and younger age in smokers (p=0.001). Unadjusted analysis identified smoking as a risk factor for lower total cognitive functional score (p=0.001) as well as lower MASQ subscale scores in language (p=0.006), verbal memory (p<0.001), visual-spatial memory (p=0.005), and attention (p=0.0031). Similarly, univariate analysis adjusting for age, gender, body mass index (BMI), marital status, and education level revealed smoking as a risk factor for lower total cognitive functional scores (p=0.009) and lower MASQ subscale scores in language (p=0.033), verbal memory (p=0.003), visual-spatial memory (p=0.018), and attention (p=0.040). In terms of secondary outcomes, unadjusted analysis identified smoking as a risk factor for greater FM symptom severity (p<0.001), worse quality of life measures of bodily pain (p=0.023) and mental component scale (p=0.009), greater fatigue (p=0.037), increased sleep problems (p<0.001), and increased anxiety (p<0.001) and depression (p=0.004). Univariate analysis adjusting for age, gender, BMI, marital status, and education level revealed smoking as a risk factor for greater FM symptom severity (p=0.003), worse quality of life measures of bodily pain (p=0.026) and mental component scale (p=0.021), greater sleep problems (p=0.012), and increased anxiety (p<0.001) and depression (p=0.037).
Conclusion: In FM patients, smoking is a risk factor for cognitive dysfunction. Moreover, FM patients who smoked were also more likely to report increased FM symptom severity, worse quality of life indices, worse sleep, and increased anxiety and depression.