Physical Activity And Sedentary Time In Adults With Down Syndrome Estimated By Different Cut Points

Abstract

Physical activity (PA) and sedentary time in persons with Down syndrome (DS) have been previously examined with accelerometry using intensity cut points developed for the general population. These cut-points may not be valid for persons with DS due to altered biomechanical and physiological responses to PA. PURPOSE: To examine if DS-specific cut-points and cut-points developed for the general population differ in estimating sedentary time and PA levels in persons with DS. METHODS: Eleven adults with DS (4 women & 7 men; age 37 ± 14 years) wore for 7 days an accelerometer (wGT3X-BT, Actigraph) on their right hip. Times sedentary and in light, moderate, and vigorous PA were assessed with three cut-point sets: (a) Troiano; (b) Freedson; and (c) DS-specific. The first two sets of cut-points were developed for the general population based on vertical axis counts. The third was developed by our group based on vector magnitude counts in 16 adults with DS. We compared sedentary time and PA variables between methods using 3×4 (method-by-intensity) within-group ANOVA. A significant interaction was analyzed with follow-up within-group ANOVA at each intensity level and post-hoc tests between methods if needed. RESULTS: A significant method-by-intensity interaction (p = 0.002) indicated that the estimates of times in sedentary and light, moderate, and vigorous PA generally differed between methods. Follow-up analysis showed that: (a) sedentary time was lower by our DS-specific cut points than the Troiano and Freedson (457 ± 131, 505 ± 149, and 517 ± 111 min·day-1, respectively; p ≤0.04); (b) light PA did not differ between methods (345 ± 37, 336 ± 85, and 346 ± 73 min·day-1, respectively; p = 0.782); moderate PA was higher by our cut points than the Troiano and Freedson (85 ± 44, 28 ± 24, and 25 ± 23 min·day-1, respectively; p <0.001); and (d) vigorous PA was higher by our cut points than the Troiano and Freedson (9.9 ± 9.2, 0.3 ± 0.8, and 0.1 ± 0.2 min·day-1, respectively; p ≤0.007). There were no differences between the Troiano and Freedson. CONCLUSIONS: Compared to cut-points for the general population, DS-specific cut-points estimate lower levels of sedentary time and higher levels of moderate and vigorous PA. Supported by NIH Grant R15HD098660