Background Morning stiffness exhibits a circadian rhythm. Its assessment is subjective and no method has been introduced yet to measure it quantitatively. Morning stiffness may cause a delay in response to a stimulus and this delay in response time can be measured electrophysiologically (1,2).
Objectives To quantify morning stiffness and to determine the relationship between disease activity and morning stiffness in patients with rheumatoid arthritis.
Methods 27 patients with rheumatoid arthritis (23 female, 4 male; with a median age 55.00 [24-74] years) were enrolled. Premotor reaction and response times of the participants were measured electromyographically. Premotor time is the interval between the stimulation and the beginning of muscle activation. Motor time is the interval between the beginning of muscle activation to perform a prespecified task and fulfillment of that task. Each subject was seated on a chair with the back supported and forearms on the lap. A button was located on a vertical platform placed in front of the patient at arm's length. With a surface stimulation electrode, a painless electrical stimulus of 5 mA was applied on the shoulder of the non-dominant side. The patient was asked to press the button in response to the stimulus. The active recording surface electrode was placed over the anterior fibers of the deltoid muscle and the reference surface electrode was placed over the acromion on the dominant side. Recordings were performed twice at 8:00 AM and 17:00 PM on the same day. Grip strength was measured by a dynamometer. Quality of life and pain were evaluated by health assessment questionnaire (HAQ) and visual analogue scale (VAS), respectively. DAS28 was also evaluated.
Results Motor time, grip strength, VAS and HAQ measurements improved significantly improved in the evening (Table 1). There was positive correlation between DAS28 and both duration (r=0.448, p=0.019) and severity (r=0.574, p=0.002) of morning stiffness, HAQ (r=0.553, p=0.003) and VAS (r=0.580, p=0.002).
Conclusions This is a preliminary trial to quantify morning stiffness. We observed a decrease in the motor reaction time in the evening which may be due to amelioration of stiffness during the day. We believe that this electrophysiological method may permit assessment of morning stiffness more objectively.
Ozyemisci-Taskiran O, Gencay-Can A, Gunendi Z, Beyazova M. A Single Dose of Indomethacin Does Not Prolong Premotor Reaction Time in Young, Healthy Adults: A Randomized, Placebo-Controlled, Double-Blind, Cross-Over Study.Double-Blind, Cross-Over Study. Turk J Rheumatol 2012;27(1):24-30.
Dickstein R, Hocherman S, Amdor G, Pillar T. Reaction and Movement Times in Patients with Hemiparesis for Unilateral and Bilateral Elbow Flexion. Phys Ther. 1993;73:374-380.
Disclosure of Interest None declared