P128 Temporal dynamics between activities and fatigue dimensions in knee osteoarthritis: an exploratory within day study
Authors: Fawole Henrietta O , Riskowski Jody L , Dell'Isola Andrea , Steultjens Martijn , Chastin Sebastien F. M 
Published: April 2020

Abstract

Background
Fatigue is believed to include both physical and mental components, suggesting there may be fatigue dimensions. Evidence suggests that physical activity (PA) and mental activity (MA) play a role on fatigue in those with knee osteoarthritis (OA); however, it is unclear how the patterns of physical and mental activity relate to fatigue and its dimensions, particularly in knee OA population. Therefore, the study aims were (1) to estimate the within day contribution of physical fatigue (PF) and mental fatigue (MF) to general fatigue (GF) and (2) to explore within day dynamic and temporal associations between PA categories, MA intensity and fatigue dimensions (PF, MF, & GF) using an ecological momentary assessment (EMA) and time series approach in individuals with doctor-diagnosed knee OA.

Methods
Twenty-three participants with self-reported doctor-diagnosed knee OA were included in this EMA study. Participants self-reported GF, PF, MF and MA intensity three times daily at designated periods for seven days using a 0-10 visual analogue scale. Concurrently, PA (step counts, standing time, light intensity physical activity [LIPA] time, LIPA+standing time and moderate-to-vigorous physical activity [MVPA] time) was measured using an activPAL accelerometer for one week. Compositional data analysis was used to estimate the contribution of within day PF and MF to GF and cross-correlation analyses to estimate within day association of PA categories, MA intensity and fatigue dimensions (PF, MF, & GF). The absolute value of cross correlation was considered significant if it fell within the 95% confidence interval of the mean.

Results
Compositional analysis revealed that PF contributed more than MF to GF within day. However, the contribution of MF to GF rose within day while PF’s contribution stayed stable. Cross-correlation analyses showed that previous GF negatively predicted future step count (r= -0.62; CI[-0.99, -0.25]), LIPA time (r= -0.62; CI[-0.99, -0.25]), LIPA + standing time (r= -0.43; CI[-0.85, -0.01]) within day. MA and GF had a bidirectional association, with MA positively predicting GF and GF negatively predicting MA intensity. A concurrent positive association was noted for MA and MF (r = 0.34; CI[0.01, 0.67]) and MF negatively predicted MA (r= -0.43; CI[-0.85, -0.01]).

Conclusion
These findings suggest higher contribution of PF to GF within day while noting the potential persistence of MF within day. Further, the within day cross-correlation support a potential reduction in GF may increase within day PA; but did not confirm a possible beneficial effect of within day increase in PA on fatigue types. GF and MF may be important components that influence MA intensity within day. Decreasing or treating MF may have positive impact on increasing MA intensity within day. It may be necessary to consider effective (daily) GF and MF treatment to increase PA and MA levels in knee OA.

Disclosures
H.O. Fawole None. J.L. Riskowski None. A. Dell'Isola None. M. Steultjens None. S.F.M. Chastin None.