Background Ankylosing spondylitis (AS) is a rheumatic inflammatory disease that mainly affects the axial skeleton. Important symptoms comprise pain, (morning) stiffness, fatigue, reduced mobility and limitations in the physical function. Likely this will lead to a decrease of physical activity (PA) compared to a healthy population.
Objectives The aim of this study was to compare patients with AS and healthy controls regarding their PA, using a tri-axial accelerometer.
Methods In this cross-sectional study, PA was measured using a tri-axial accelerometer (Actigraph GT3X+) attached to the lower back by means of an elastic belt. Subjects wore the accelerometer for 7 consecutive days, during waking hours. From accelerometer output, total activity counts per day was calculated, as well as the average minutes per day subjects spent in light i.e. <3.00 Metabolic Equivalent of Task (MET), moderate (3.00-5.99 MET) vigorous (6.00-8.99 MET) or very vigorous activity (>8.99 MET). Subjects also completed an online questionnaire including the BASDAI (disease activity, 0 no symptoms to 10 worst symptoms), BASFI (limitations in physical function, 0 no limitations to 10 most limitations), disease duration in years (patients only), height and weight.
Results A total of 135 AS patients (mean age 51 ± 13 y; 60% males; disease duration of 17 ± 12 y) and 100 healthy controls (mean age 44 ± 12 years; 66% males) were included. Patients with AS were significantly older, P <0.001 and had a mean ± SD body mass index (BMI) in kg/m2 of 26.0 ± 4.3, compared to 24.8 ± 5.0 in controls (NS). Patients showed the same total amount of PA as well as time spent in low and moderate activity as controls (Table 1). Controls spent slightly more time in vigorous and very vigorous PA. Patients reported significantly higher on the BASDAI 4.3 ± 2.2 and BASFI 4.1 ± 2.6 opposed to controls 1.3 ± 1.2 and 0.38 ± 0.7 respectively, (both P <0.001).
Conclusions Despite experiencing more limitations and disease activity, patients with AS scored a similar amount of total PA as controls and spent equal time in light and moderate PA, except for vigorous and very vigorous PA even though the patients were older. This study indicates the importance of including objective measures of physical functioning in patients with AS.
Disclosure of Interest S. van Genderen: None Declared, A. Boonen Grant/research support from: MSD, Pfizer, Amgen, Abbott, Consultant for: Pfizer, Speakers bureau: Pfizer, UCB, P. Jacobs: None Declared, L. Heuft: None Declared, J. Luime: None Declared, A. Spoorenberg: None Declared, S. Arends: None Declared, D. van der Heijde: None Declared, R. Landewe: None Declared, G. Plasqui: None Declared