Sensitization in office workers with chronic neck pain in different pain conditions and intensities

Objectives
Office workers with chronic neck pain demonstrates signs of widespread hyperalgesia, less efficient descending pain modulation, which could indicate sensitization of central pain pathways. No studies have assessed a wide variety of office workers with different chronic neck pain disorders and assessed the impact of pain intensity on assessments of central pain pathways. This study aimed to assessed pressure pain thresholds (PPTs), temporal summation of pain (TSP) and conditioned pain modulation (CPM) and to associate these with pain intensity and disability in subgroups of office workers.

Methods
One hundred-and-seventy-one office workers were distributed into groups of asymptomatic and chronic neck pain subjects. Chronic neck pain was categorized as chronic trapezius myalgia and chronic non-specific neck pain and as ‘mild-pain’ (Visual Analog Scale [VAS]≤3) and ‘moderate-pain’ (VAS>3) groups. PPTs, TSP, CPM, and Copenhagen Psychosocial Questionnaire II were assessed in all subjects. Neck Disability Index and Pain Catastrophizing Scale were assessed in all the symptomatic office workers.

Results
PPTs were lower in moderate pain (n=49) and chronic trapezius myalgia (n=56) compared with asymptomatic subjects (n=62, p<0.05). TSP was facilitated in moderate pain group compared with mild pain (n=60, p<0.0001) group and asymptomatic subjects (p<0.0001). No differences were found in CPM comparing the different groups (p<0.05). Multiple regression analysis identified Neck Disability Index and TSP as independent factors for prediction of pain intensity in chronic trapezius myalgia (R2=0.319) and chronic non-specific neck pain (R2=0.208). Somatic stress, stress and sleep as independent factors in chronic non-specific neck pain (R2=0.525), and stress in moderate pain group (R2=0.494) for the prediction of disability.

Conclusions
Office workers with chronic trapezius myalgia and moderate pain intensity showed significant signs of widespread pressure hyperalgesia. Moreover, the moderate pain group demonstrated facilitated TSP indicating sensitization of central pain pathways. Neck Disability Index and TSP were independent predictors for pain intensity in pain groups. Sleep and stress were independent predictors for disability.