Objectively measured physical activity and sedentary time in young adults born preterm-The ESTER study

Background: Young adults born preterm have higher levels of cardio metabolic risk factors and they report less physical activity than their peers born at term. Physical activity provides important cardio metabolic health benefits. We hypothesized that objectively measured physical activity levels are lower and time spent sedentary is higher among preterm-born individuals compared with controls. Methods: We studied unimpaired participants of the ESTER birth cohort study at age 23.3 y (SD: 1.2): 60 born early preterm (<34 wk), 108 late preterm (34–36 wk), and 178 at term (controls). Physical activity and sedentary time were measured by hip-worn accelerometer (ActiGraph). Results: As compared with controls’ (mean physical activity, 303 counts per minute (cpm; SD 129)), physical activity was similar among adults born early preterm (mean difference = 21 cpm, 95% CI −61, 19) or late preterm (5 cpm, −27, 38). Time spent sedentary was also similar. Adjustments for early life confounders or current mediating characteristics did not change the results. Conclusion: In contrast to our hypothesis, we found no difference in objectively measured physical activity or time spent sedentary between adults born preterm and at term. The previously reported differences may be limited to physical activity captured by self-report. Follow-up studies of adolescents and adults born preterm suggest that those born smallest report less physical activity and are less fit than term-born individuals (1,2,3,4). The differences can be substantial: as assessed by a comprehensive 12-mo physical activity questionnaire, unimpaired adults born preterm at very low birth weight (< 1,500 g) report over 50% lower energy expenditure from leisure-time conditioning physical activity than controls born at term (3). This may contribute to the increased cardio metabolic risk profile reported in this group (5,6). However, these infants constitute only a minority of preterm infants; for example, in the United States, 70% of preterm infants are born late preterm, between 34 and 36 wk of gestation (7). Recent studies have suggested that the adverse cardio metabolic risk profile and perhaps levels of physical activity, and in parallel muscular fitness, decrease with an increasing degree of prematurity and may extend to those born late preterm (8,9). Promoting increased physical activity and decreased sedentary time is important for preventing cardio metabolic risk (10,11). However, few studies have measured physical activity and sedentary time objectively in adults born preterm (12,13,14). We hypothesized that objectively measured physical activity levels are lower and sedentary time higher among preterm-born individuals and that there is a dose-response relationship between the degree of prematurity and physical activity and sedentary time