Factors Influencing Cognitive Impairment in Neuropathic and Musculoskeletal Pain and Fibromyalgia.

Objective: To assess cognitive performance of chronic pain (CP) patients diagnosed with three types of pain-neuropathic pain (NP), musculoskeletal (MSK), and fibromyalgia (FM)-and to analyze the factors influencing cognitive difficulties in each group.

Methods: Two hundred fifty-four CP patients-104 NP, 99 MSK, 51 FM-and 72 pain-free subjects were included in the study. The "Test Your Memory" (TYM) scale was used to assess cognitive performance. Pain intensity was measured by means of the visual analog scale (VAS); the Hospital Anxiety and Depression scale was used to assess mental status, and the Medical Outcome Study (MOS) sleep scale to assess sleep quality. The relationships between cognitive performance and these factors were analyzed using linear regression models.

Results: The mean score in the TYM was significantly lower (worse cognitive function) in CP patients than controls (40.5 vs 43.9, P < 0.001). In the separate analysis of each group, depression was observed to have a negative impact on MSK pain patients (ß = -0.37, 95% confidence interval [CI] = -0.53 to -0.2, P < 0.001) and on FM subjects (ß =-1.01, 95% CI = -1.05 to -2.38, P = 0.022). A significant interaction between pain intensity and depression was observed in the FM patients. In addition, a U-shaped association was found between the duration of pain and cognitive performance in the NP patients. Neither anxiety nor sleep impairment affected cognitive performance in any of the CP patients.

Conclusions: These results highlight the importance of taking into account the type of pain when assessing cognitive performance in CP patients and demonstrate the influence of the emotional state of the patient, especially if depression is present.