Characterization and Agreement Between Application of Mobile Ecological Momentary Assessment (mEMA) and Accelerometry in the Identification of Prevalence of Sedentary Behavior (SB) in Young Adults

Introduction
Sedentary behavior (SB) is defined as any activity performed during “awake” time with low energy expenditure (equal to or below 1.5 metabolic equivalents – MET’s) in a sitting or reclining position (Sedentary Behaviour Research Network, 2012; Tremblay et al., 2017). Studies have shown that this behavior is highly prevalent among adults, and most of the time awake (62%) is spent on this type of activity (Hansen et al., 2012) and that the mean percentage of SB, weighted by the total time of accelerometer use per day in a sample of the National Sample of the United States was from 35 to 82.3% (Evenson et al., 2015).

These high SB prevalence rates demonstrated in epidemiological studies indicates that SB is associated with all-cause and cardiovascular morbidity and mortality in adults (Young et al., 2016). Additionally, a recent study based on data for more than 1 million participants in 19 studies has shown that daily sedentary time is log-linearly associated with increased risk of all-cause mortality in adults and suggest that the ideal situation is to spend less than 9 h per day when referring to all-cause mortality (Ku et al., 2018).

Methodologies for assessing SB include self-report and objective measurement, and each provides distinct information and has different limitations (Gibbs et al., 2015). While self-report depends on participant’s ability to remember past activities, objective measurement is not able to identify the different contexts where behavior occurs (Healy et al., 2011; Atkin et al., 2012). Recently, researchers have indicated the need for the development and validation of novel devices capable of assessing posture and standardization of research practices for SB assessment by accelerometry (Gibbs et al., 2015). Ecological Momentary Assessment (EMA) (Shiffman et al., 2008; Atkin et al., 2012) using mobile phones, such as the Mobile Ecological Momentary Assessment (mEMA) application (Runyan and Steinke, 2015) has potential to capture information about the context in which the behavior occurs and the type of activity being performed (Loveday et al., 2016).

A recent study examined the association between EMA records for TV, video, and game use with objective measures of sedentary time in children measured by accelerometer during a 2-h observation window found that EMA records are highly related to the accelerometer measurement. Therefore, understanding the relationship between EMA and accelerometry can optimize future studies aimed at assessing activities and health outcomes (Zink et al., 2018). In adults, few studies have been conducted to verify the validity or agreement between objective SB methods and EMA, and in addition different criteria have been used in data interpretation (Dunton et al., 2012; Liao et al., 2014; Bruening et al., 2016; Knell et al., 2017). The use of EMA in combination with objective measurements (Dunton et al., 2012) can provide information about the presence or absence of SB in different contexts. Until then, studies have been aimed at verifying the relationship between total SB time and health outcomes, but with the possibility for researchers to identify the time spent in SB in different contexts, these new relationships with health outcomes still need to be investigated (Busschaert et al., 2015).

The evidence that SB is associated to health outcomes is still limited because these relationships are almost exclusively measured by self-report (Gibbs et al., 2015) and little explored by methods like EMA, which can obtain information about the context of SB. Therefore, the aim of this study was to describe SB in the physical, social, and environmental contexts and verify the agreement between the application of mEMA and accelerometry in the identification of SB in young adults.