High Fragmented Physical Activity as an Early Risk Indicator of Frailty and Mortality in Adults Aged 50 Years and Over

INTRODUCTION: This study aimed to explore the associations of activity fragmentation with frailty status and all-cause mortality in a representative US sample of people 50 years and over. METHODS: This prospective study used data from the 2003-2006 waves of the National Health and Nutrition Examination Survey (NHANES). Participants 50 years or over were included in the study (n = 2,586). Frailty status was assessed using a valid modification of the Fried criteria. Linked data from the National Death Index registry were used to ascertain mortality. Physical activity fragmentation was measured by accelerometry. To calculate activity fragmentation, an active-to-sedentary transition probability was calculated as the number of physical activity bouts divided by the total sum of minutes spent in physical activity. Age, gender, ethnicity, education, mobility issues, drinking status, smoking status, BMI, and self-reported chronic diseases were reported in the NHANES study. RESULTS: An increment of 1 SD in activity fragmentation was associated with an increased likelihood of frailty (odds ratio [95% confidence interval] = 1.36 [1.13-1.664]). Compared with participants in the high activity fragmentation/low physical activity category, participants in the low activity fragmentation/low physical activity and low activity fragmentation/high physical activity categories were associated with a lower likelihood of frailty. We found a nonlinear association between activity fragmentation and all-cause mortality. Compared with participants in the high activity fragmentation/low physical activity category, participants in the low activity fragmentation/low physical activity, low activity fragmentation/high physical activity, and high activity fragmentation/high physical activity categories were associated with a lower mortality risk. Participants with a low fragmented activity pattern may also overcome some of the detrimental effects associated with sedentary behavior. CONCLUSIONS: Our results suggest that a high fragmented physical activity pattern is associated with frailty and risk of mortality in adults and older adults. This association was independent of total volume of physical activity and time spent sedentary.