SP426
THE IMPACT OF HAEMODIALYSIS ON PHYSICAL ACTIVITY AND RECOMMENDATIONS FOR THE STANDARDISED ASSESSMENT OF ACTIVITY MONITOR DATA

INTRODUCTION: Physical activity (PA) is exceptionally low amongst the haemodialysis (HD) population, and physical inactivity is a powerful predictor of mortality, making it a prime focus for intervention. Objective measurement of PA using accelerometers is increasing, but standard reporting guidelines essential to effectively evaluate, compare and synthesise the effects of PA interventions are lacking. This study aims to: describe PA levels of HD patients, including the impact of HD days, weekdays (WD) and weekends (WE); determine the measurement and processing guidance required to ensure representative PA data amongst a diverse population.

METHODS: 77 HD patients, (64% men, age 56±14 years, time on HD 40 (IQR 19-72) months, 40% Chinese, 34% White British, 22% Indian, CCI 3 (IQR 2-5)) wore an accelerometer for 7 days.

Step count and wear-times were extracted for a range of wear-time criteria (≥1-12 hours). Analysis of step count and wear-time between types of day (HD, WD, WE) across a range of minimum wear time criteria were conducted using repeated measures ANCOVA. Intraclass correlation coefficients (ICCs) were used to determine the reliability of the data, with an ICC of ≥0.80 deemed acceptable. The Spearman-Brown prophecy formula was used to estimate the minimum number of days required to obtain representative PA data. The influence of applying these minimum number and increasing wear-time on sample size retention was examined, with an acceptable sample size retention set at 80%.

RESULTS: Participants wore the monitor for fewer minutes on HD days than both WD and WE (803 [95%CI 759-847] versus 951 [95%CI 913-989] minutes and 972 [95%CI 934-1009] minutes p<0.001, respectively). This was driven by poor adherence with accelerometer wear for 37% (1.5±1.3 hours) of the HD session.

Patients took fewer steps on HD days compared with WD and WE (3402 [95%CI 2665-4140] versus 4914 [95%CI 3940-5887] and 4633 [95%CI 3558-5707] steps/day, p<0.001). Findings were unchanged after controlling for wear-time.

Given that there were no statistically significant differences between WD and WE, these data were pooled into non-HD days. ICCs on HD days across wear-time criteria ≥7 hours were >0.80 (ICC 0.815-0.839) and were greater than ICCs for wear-time criteria on non-HD days (ICC 0.0559-0.611). Spearman-Brown calculations indicated that a minimum of 1 HD day and 3 non-HD days are required to provide representative data. The most stringent wear-time criterion retaining 82% of the sample was ≥ 7 hours.

CONCLUSIONS: Activity levels within HD patients are low, particularly on HD days. At group level, a wear-time of ≥7 hours on one HD day and three non-HD days is required to provide reliable PA data whilst retaining an acceptable sample size. Standardised assessment of PA will enhance data quality and ensure that PA interventions can be effectively evaluated, compared and synthesised.