These studies indicate that analysis of the data using 60-s epochs and a vertical magnitude cut-point < 200 cpm or using 30- or 60-s epochs with a machine learning algorithm provides the most valid estimates of SB .
Conclusions Few studies have examined the reliability and validity of accelerometers for measuring SB  in older adults .
Studies to date suggest that the criteria research ers use for classifying an epoch as sedentary instead of as non-wear time ( e.g. , the non-wear algorithm used ) may need to be different for older adults than for younger adults .
The required number of hours and days of wear for valid estimates of SB in older adults was not clear from studies to date .
Background The evidence showing the ill health effects of prolonged sedentary behaviour ( SB ) is growing .
Most studies of  SB in older adults have relied on self-report measures of SB .
However , SB is difficult for older adults to recall and objective measures that combine accelerometry with inclinometry are now available for more accurately assessing SB .
The aim of this systematic review was to assess the validity and reliability of these accelerometers for the assessment of  SB in older adults .
Impact of accelerometer data processing decisions on the sample size, wear time and physical activity level of a large cohort study
Background Accelerometers objective ly assess physical activity ( PA ) and are currently used in several large-scale epidemiological studies , but there is no consensus for processing the data . This study compared the impact of wear-time assessment methods and using either vertical (V)-axis or vector magnitude ( VM ) cut-points on accelerometer output . Methods Participants ( 7,650 women , mean age 71.4 y ) were mailed an accelerometer ( ActiGraph GT3X+ ) , instructed to wear it for 7 days , record date s and times the monitor was worn on a log , and return the monitor and log via mail . Data were processed using three wear-time methods ( logs , Troiano or Choi algorithms ) and V-axis or VM cut-points . Results Using algorithms alone result ed in " mail-days " incorrectly identified as " wear-days " ( 27 - 79 % of subjects had > 7-days of valid data ) . Using only date s from the log and the Choi algorithm yielded : 1 ) larger sample s with valid data than using log date s and times , 2 ) similar wear-times as using log date s and times , 3 ) more wear-time ( V , 48.1 min more ; VM , 29.5 min more ) than only log date s and Troiano algorithm . Wear-time algorithm impacted sedentary time ( ~30 - 60 min lower for Troiano vs. Choi ) but not moderate-to-vigorous ( MV ) PA time . Using V-axis cut-points yielded ~60 min more sedentary time and ~10 min less MVPA time than using VM cut-points . Conclusions Combining log- date s and the Choi algorithm was optimal , minimizing missing data and research er burden . Estimates of time in physical activity and sedentary behavior are not directly comparable between V-axis and VM cut-points . These findings will inform consensus development for accelerometer data processing in ongoing epidemiologic studies
These studies indicate that analysis of the data using 60-s epochs and a vertical magnitude cut-point < 200 cpm or using 30- or 60-s epochs with a machine learning algorithm provides the most valid estimates of SB .
Conclusions Few studies have examined the reliability and validity of accelerometers for measuring SB  in older adults .
Studies to date suggest that the criteria research ers use for classifying an epoch as sedentary instead of as non-wear time ( e.g. , the non-wear algorithm used ) may need to be different for older adults than for younger adults .
The required number of hours and days of wear for valid estimates of SB in older adults was not clear from studies to date .
Background The evidence showing the ill health effects of prolonged sedentary behaviour ( SB ) is growing .
Most studies of  SB in older adults have relied on self-report measures of SB .
However , SB is difficult for older adults to recall and objective measures that combine accelerometry with inclinometry are now available for more accurately assessing SB .
The aim of this systematic review was to assess the validity and reliability of these accelerometers for the assessment of  SB in older adults .