Prolonged bouts of sedentary time are associated with 2-hr plasma glucose, independent of total sedentary time

Abstract

Total sedentary time is associated with increased 2-hr plasma glucose. However, total sedentary time does not indicate how the sedentary time was accumulated. Animal studies suggest that longer, uninterrupted bouts of sedentary time have more detrimental metabolic effects compared with shorter accumulated bouts. We examined if longer average bouts of sedentary time were associated with higher 2-hr plasma glucose, independent of total sedentary time. In total, 67 men and 106 women (mean age 53.3, range 30 to 87) without known diabetes were recruited from the 2004-2005 AusDiab study. Sedentary time was measured by accelerometers worn during waking hours for seven consecutive days, and summarised as total sedentary time (counts/minute < 100, hours), total number of sedentary bouts, and mean sedentary bout time (minutes). A sedentary bout was defined as the sum of minutes of <100 accelerometer counts. An oral glucose tolerance test determined 2-hr plasma glucose. Mean sedentary bout time was 6.0 minutes (range 3.0 to 11.3). After adjusting for age, sex, total sedentary time, moderate-to-vigorous intensity physical activity, and time accelerometer worn, mean sedentary bout time was significantly associated with higher 2-hr plasma glucose (b=0.28, 95%CI 0.07 to 0.49, p=0.010). Additionally, total number of sedentary bouts (reflecting more breaks in sedentary time) was significantly associated with lower 2-hr plasma glucose (b=-0.04, -0.06 to -0.01 per 10 bouts, p=0.003). These findings provide preliminary evidence on the potential importance for human health of avoiding prolonged periods of being sedentary, and provide a key step towards formulating sedentary behaviour recommendations.