Best-evidence synthesis

To enable conclusions on associations between sedentary behaviour and stress on the basis of the methodological quality of studies, a best-evidence synthesis [29] was conducted by two authors (MT and LDS). Due to the heterogeneity in exposure and outcomes, a best-evidence synthesis was selected over a meta-analysis given it would not be meaningful to calculate the average effect as per a meta-analysis [29, 30]. This method has been used previously in systematic reviews in the area of sedentary behaviour and health outcomes [22, 31, 32]. Adapted from guidelines outlined in previous reviews that applied best-evidence synthesis [22, 31], the evidence was graded as strong, moderate, or insufficient. Consistency was defined on two levels: 1) within a study (i.e. ≥75% of results in same direction within a study), to account for multiple modelling; and 2) between studies (i.e. ≥75% of results in same direction across studies examined). Strong evidence was defined as consistent results in ≥2 strong/moderate quality studies. Moderate evidence was defined as consistent results in one strong/moderate quality study and at least one weak-quality study; or consistent results in ≥2 weak-quality studies. Insufficient evidence was defined as having only one available study or inconsistent results in ≥2 studies. When ≥2 studies were of strong/moderate methodological quality, those with weak-quality were disregarded in the evidence synthesis [31]. In this manner, evidence was weighted in terms of study design/methodological quality.

To determine whether associations between time in sedentary behaviour and stress could be explained by the nature of the sedentary behaviour and stress measures, studies were grouped and results analysed firstly on the basis of utilising objective versus self-report measures of stress, and secondly, on the use of objective (i.e. device assessed or direct observation) and self-report measures of sedentary behaviour.