A large accelerometry-based analysis of the Cancer Prevention Study–3 revealed extended sedentary behavior and limited vigorous physical activity among U.S. adults.

In the study, published in BMJ Journals and conducted by the American Cancer Society, researchers tracked 21,219 adult participants using ActiGraph GT3X+ accelerometers to measure physical activity over multiple days.

Among the 23,111 participants initially enrolled, 91.8% returned devices with complete wear logs. The researchers noted that 90.6% (n = 20,950) of them provided at least 3 adherent days of data with a minimum wear time of 10 hours per day.

The participants were predominantly female (77.3%) and non-Latino White (85.8%), with an average age of 58. The median daily wear time was 15.3 hours.

The researchers found that the median sedentary time was 9.4 hours (564 minutes) per day, with an interquartile range (IQR) of 171 minutes. The median moderate activity was 29 minutes per day (IQR = 36), while the median vigorous activity was just 3 minutes per day (IQR = 13). Participants had a median of 6,474 steps per day (IQR = 5,348). The researchers also found consistent device wear time across days. 

As part of a broader investigation launched between 2006 and 2013, the Cancer Prevention Study–3 Accelerometry Substudy aimed to explore links between physical activity, sedentary time, and health outcomes, particularly future cancer incidence and survival. Future data will be linked with the National Death Index and state cancer registries biennially, with triennial surveys planned for the next 20 years.

Strengths of the study include its large cohort size, objective data collection, and high adherence rates. However, the participant group—primarily older, non-Latino White participants—may limit generalizability.

Another potential limitation of this subcohort was the 3.5-year duration of data collection, partly because of a 6-month pause at the onset of the COVID-19 pandemic.

"Timing of data collection around the pandemic may also be a limitation because studies (including one study using self-reported data within CPS-3) suggest that the pandemic may have affected usual physical activity and sedentary time patterns," wrote lead study author Erika Rees-Punia of the Department of Population Science at the American Cancer Society, and colleagues.