Atkin, Andrew J4; Ekelund, Ulf4; Møller, Niels Christian5; Froberg, Karsten5; Sardinha, Luis B4; Andersen, Lars Bo5; Brage, Soren4
1 Department of Sports Science and Clinical Biomechanics, Det Sundhedsvidenskabelige Fakultet, SDU2 Research in Childhood Health (RICH), Department of Sports Science and Clinical Biomechanics, Det Sundhedsvidenskabelige Fakultet, SDU3 Exercise Epidemiology, Department of Sports Science and Clinical Biomechanics, Det Sundhedsvidenskabelige Fakultet, SDU4 unknown5 Department of Sports Science and Clinical Biomechanics, Det Sundhedsvidenskabelige Fakultet, SDU
Influence of Accelerometer Processing on Health Relations
PURPOSE: Accelerometry is increasingly being used to assess sedentary time in epidemiological studies, yet the most appropriate means of processing this data remains uncertain. This cross-sectional study examined the influence of selected accelerometer cutpoints and non-wear criteria on associations of sedentary time with adiposity and clustered metabolic risk. METHODS: Data were from the European Youth Heart Study, which included assessment of sedentary time by accelerometer. Sixteen sedentary time variables were constructed based upon combinations of frequently used cut-points (100, 500, 800, 1100 counts-per-minute) and non-wear criteria (10-, 20-, 60-, 100-min consecutive zeros). Adiposity was assessed by sum of four skin-fold thickness measures. A clustered metabolic risk score was calculated as the mean of standardised metabolic syndrome components, including blood pressure, insulin resistance, and inverted fasting HDL-cholesterol. Analyses were conducted using multi-level cross-sectional time-series regression, adjusted for overall physical activity (accelerometer counts per minute). Meta-analysis was used to obtain pooled estimates of the exposure-outcome association over all processing protocols; meta-regression was used to determine the influence of non-wear and cut-point protocol on observed associations. RESULTS: Sedentary time follows a power law with cut-point (exponent=0.27) and zero-string (exponent=0.03), and was positively associated with clustered metabolic risk (β = 0.0051, 95%CI 0.0018, 0.0085). The association was moderated by cut-point, with higher cut-points typically producing stronger associations. No significant association between sedentary time and adiposity was observed. CONCLUSION: Choice of accelerometer cut-point may moderate the association between sedentary time and clustered metabolic risk, suggesting that direct comparisons of associations between studies using different cut-points must be made with caution.
Medicine and Science in Sports and Exercise, 2013, Vol 45, Issue 6