Effect of night-time data on sedentary and upright time and energy expenditure measured with the Fibion accelerometer in Emirati women

Background and aims: Wearing an accelerometer during night-time could conflate sedentary behavior time and sleep hours. It is important to assess the impact of including night-time data on sedentary and upright behavior in a sedentary population. Therefore, we investigated differences in sitting and upright time and associated energy expenditure (EE), recorded by a Fibion accelerometer, with and without night-time data in Emirati women working in desk-based jobs. Methods: Thirty-one healthy Emirati women working in the government offices used the Fibion accelerometer for a week. Fibion data were included if the participants wore the device for ≥600 min per day for a minimum of three weekdays and one weekend day. Sedentary (sitting) and upright time and associated energy expenditure (EE) were recorded using the Fibion. Variables were compared with and without night-time data using the paired t tests or Wilcoxon signed-rank tests. Effect sizes were determined using Cohen's d. Results: Statistically significant differences for 15 out of 18 variables were observed when the night-time data were included. Except for cycling time, cycling EE, and vigorous activity time, nearly all other outcome measures showed a significant increase (moderate to large effect sizes) with night-time data compared to those without night-time data. Conclusions: Cycling time/EE and vigorous activity time did not change with standard night-time data. Therefore, studies examining only cycling and/or vigorous activity time with the Fibion accelerometer do not require night-time data removal. An analysis of other variables relating to sedentary and upright time will require night-time data exclusion.